GTU
CHEM 114
GENERAL
CHEMISTRY
LABORATORY-II
BOOKLET
2017 SPRING
1
PREFACE
Üniversitelerde Fen bölümleri, tıp ve mühendislik öğrencileri ilk yıllarında Kimya
Laboratuvarı dersi ile karşılaşmaktadır. Kimya Laboratuvarı dersi ile ilgili bu kitapçığın
başında öncelikle kimya laboratuvarı için son derece önemli olan kimya laboratuvarında
uyulacak kurallar ve laboratuvarda alınması gereken güvenlik önlemleri açıklanmıştır.
Laboratuvar güvenliği ile ilgili detaylı bilgiler, verilen web bağlantısındaki kaynakta yer
almaktadır.
Kimya Laboratuvarında kullanılan malzemelerin tanıtıldığı bölümden sonra,
Genel Kimya Ders konuları ile bağlantılı seçilen deneylerin föyleri yer almaktadır.
Laboratuvara ilk geldiğiniz gün, kimya laboratuvarında uyulacak kurallar ve
laboratuvarda alınması gereken güvenlik önlemleri konularında bilgilendirilerek, yangın
tüpleri, güvenlik duşu, göz yıkama muslukları gibi kaza anında kullanılacak malzeme ve
sistemlerin yerleri ve nasıl çalıştıklarını öğreneceksiniz.
Kimya laboratuvarları, her an istenmeyen kazaların yaşanabileceği yerler olması nedeni
ile herşeyden önce güvenlik konularındaki bilgilerin öğrenilmesi çok önemlidir. İlk hafta
güvenlik kuralları ve önlemleri bölümünü ve her deney haftası deney föyünü mutlaka okuyup
öğrenerek geliniz.
Hepinize sağlıklı, başarılı ve kazasız bir eğitim, öğretim dönemi dilerim.
Saygılarımla
Prof. Dr. Ayşe Gül GÜREK
Kimya Bölüm Başkanı
2
CONTENT
PREFACE ......................................................................................................................... 2
CONTENT ........................................................................................................................ 3
LABORATORY RULES FOR KIM 114 GENERAL CHEMISTRY LAB.II COURSE 4
LABORATORY EQUIPMENTS ................................................................................... 11
EXPERIMENT 9: INVESTIGATION OF THE PRINCIPLE OF VOLTA BATTERY 16
EXPERIMENT 10: ELECTROLYSIS OF WATER ...................................................... 18
EXPERIMENT 11: DETERMINATION OF REACTION ENTHALPY ..................... 21
EXPERIMENT 12: SOLID SOAP ................................................................................. 26
EXPERIMENT 13: LEAD IODIDE PRECIPITATION REACTION ........................... 29
EXPERIMENT
14:
SEPARATION
OF
MIXTURES
OF
LIQUIDS
BY
DISTILLATION ............................................................................................................. 35
EXPERIMENT 15: SYNTHESIS OF NYLON 6,6 ....................................................... 38
DENEY16:MOLECULAR WEIGHT DETERMINATION USING FREEZING POINT
DEPRESSION ................................................................................................................ 42
3
LABORATORY RULES FOR KIM 11 4 GENERAL CHEMISTRY LAB.
II COURSE
1. The students must attend the General Chemistry Laboratory course in exact day, time and
laboratory which is declared on the course programs’s of the departments.
2. Attendance compulsion is %80 for the laboratory semester. If a student will not attend for 2
experiment a VF will be issued.
3. During the lab course, the students have to wear their lab coat, lab goggles and latex gloves. The
students must bring their own lab coat, lab goggles and latex gloves to the lab. If the student does not
bring lab coat, lab goggles and latex gloves to the lab or not use these items in the lab, she/he will not
be allowed to attend the lab. It will be failed in the experiment.
4. If the student will be late more than 10 minutes to the lab course, she/he will not to be allowed to
attend the lab. and the experiment.
5. During the lab course, it is strictly forbidden to use mobile phone. The students do not leave the lab
and experiment set without permission of the lab assistant.
6. In order to provide life safety and to ensure the success of experiment in a safe manner, hand jokes
between the students is strictly forbidden. Also, touching to chemicals without gloves, sniffing and
tasting them are dangerous.
7. In every experiment, chemicals and materials for the experiment will be supplied to the students by
lab assistants. The students will not borrow the chemicals and materials from the other students. At the
end of the each experiment, all the glass or metal materials will be cleaned by the students. Also, the
experiment set will be tidy and clean.
8. Before coming to lab, the students should know about the procedure of the experiment and
theoretical information.
9. In every week, at the beginning of the lab course, the quiz will be applied to the students about the
experiment of the week.
10. The total grade of an experiment will be the sum of the report grade (%50) and quiz grade (%50).
11. The passing grade of General Chemistry Laboratory course will be average of the all experiment
grades for the semester
12. At the beginning of the semester, the students will be informed about the safety rules of laboratory.
4
13. The health reports must be handed over within 5 days to the lab assistant. Students who do not
obey the rules and fulfill the requirements of the lab.will be considered as not attended to the lab. (
look at entries 1, 3, 4, 11) and no reports for the mentioned lab. session will be accepted.
14. Make-up experiments will be available for only those with health reports.
5
LABORATORY SAFETY RULES AND CAUTIONS
1. All students have to wear lab. coat and students without lab coat will not be allowed
in the lab.
2. All students have to wear safety glasses in the lab. and students without safety glasses
will not be allowed in the lab. Contact lances are not allowed in the lab. because acid and
organic chemical vapors could get in between eye and lances, lances can be glued on the eye
in the case of an accident and can be diffıcult to remove.
3. Wide dresses, sandal type shoes shouldn’t be worn in the lab. and long hair should be
tied.
4. Food, drink and chewing gum are not allowed in the lab.
5. All students should know where the fire extinguisher, first aid cabinet and shower are
placed in the lab.
6. Learn the speediest exit from the lab. in the case of a fire.
7. Use the shower when your dresses or hair catches fire.
8. Do not run and do not make jokes in the chemistry lab.
9. Benches should not be used to sit on or to leave bags or personal things.
10. Smoke and vapor released during chemical reactions should not be smelled directly.
11. It is not allowed to work in chemistry labs. without attendance of assistants or
instructors.
12.Do not use Bunsen burners next to flammable chemicals (i.e. ethers)
13.Read the labels carefully on the bottle before use of any chemicals.
14. Read the experimental procedure before coming to the lab. Students who comes to
lab having no knowledge about experiment could create risks for themselves and other
students.
15.In the case of any accident (glass cut, acid/base burn, fainting etc.) immediately
inform your assistant or instructor.
16. Do not orientate the test tube toward yourself and your friend. Reaction carried out
in the test tube could be dangerous.
17.Water should not be added on concentrated acids. Acids should be added to the water
slowly and by stirring.
6
18.It is forbidden to smell and to taste the chemicals and to pull solutions by mouth
when using pipet.
19. Chemicals (solid, liquid or solution) must not dumped into the sink. Waste bottles in
the lab. should be used. (Learn where the waste bottles in the lab are.)
20.Use the ‘’ broken glass labeled container in the lab for the broken glass pieces.
21. Matchstick, litmus paper must not be disposed to the sink.
22. Mercury vapor is invisible and toxic. Mercury in the broken thermometer is very
dangerous. You must inform your assistant.
23. Materials like hot test tube, crucible, and beaker must not hold by hand. Tube tongs
should be used or left to cool on an asbestos wire.
24. Please use the amounts of chemicals given in the procedure. Use of excess amounts
can make difficult to control the reactions or cause the side reactions.
25. Left behind chemicals should not be returned to the stock bottles, should be
discarded into the waste bottle
26. Always keep clean your working area, balance and its environment. Work clean and
tidy in the lab.
27. Don’t change the locations of the chemicals during the experiment.
28. At the end of the experiment, hand in all the materials you used to your assistant as
cleaned.
29. Make sure of that gas and water taps are closed before leaving the lab.
30. Wash your hands before leaving the lab.
31. Learn the information given in the link below and Table 1.
http://www.gtu.edu.tr/Files/kimyaBolumu/documents/LabGuvenlik.pdf
This web page is important for Lab. Security Examination
7
The following cases, must be notified firstly to the assistant or lecturer.
BURN: expose the burned area to the tap water (5-10 CUT / INJURY: Wash with water
min.), apply first aid.
and apply first aid.
FAINTING: Provide fresh air. Lay down and put the FIRE:
(Notify
the
assistant
head lower than the body.
immediately) Put the bunsen burner
off. Use shower in case of hair and
clothes caches fire. Use the fire
extinguisher when necessary.
BLEEDING: compress on the wound, keep the wound CHEMICAL SPILL: clean in a
above the heart level and get medical help.
manner appropriate to the chemical.
Aqueous solutions can be removed
with water. Information your assistant.
ACID BURNS: Use NaHCO3 solution
CHEMICALS SPILLED IN THE
EYE: The Eye is washed immediately
BASE BURNS: Use Boric acid or Acetic acid solution
with plenty of water for at least 15
minutes (use the eye-wash shower
rooms) Get medical help.
8
Laboratory Security Symbols
Anlamı
Symbols
E (Explosive): Patlayıcı
Kıvılcım, ısınma, alev, vurma, çarpma ve sürtünmeye maruz
kaldığında patlayabilir (R1-R3). Ateş, kıvılcım ve ısıdan uzak
tutulmalıdır. Uygun mesafede durulmalı ve koruyucu giysi
giyilmelidir.
F (Flammable): Yanıcı, parlayıcı
F+ (Extremely Flammable): Aşırı yanıcı, parlayıcı
Yanıcı ve parlayıcılardır (R10-R12). Alevlenme noktası sıfır
derecenin altı ve kaynama noktası maksimum 35 derece olan
sıvılar. Ağız, deri ve solunum yolu ile zehirlenmelere yol açar.
Vücut ile temas ettirmemelidir. Ateş, kıvılcım ve ısıdan uzak
tutulmalıdır.
O (oxidative): Oksitleyici
Havasız ortamda bile alev alabilir veya yanabilirler (R7-R9).
Yanabilir maddelerle karıştırıldıklarında patlayabilirler. Yanan
maddelerle teması önlenmelidir. Ateş, kıvılcım ve ısıdan uzak
tutulmalıdır. Uygun mesafede durulmalıdır. Uygun mesafede
durulmalıdır ve koruyucu giysi giyilmelidir.
G (Gas): Gaz
Basınç altında gaz içerir. Çıkan gaz soğuk olabilir. Isıtılırsa
patlayabilir. Deriye ve göze temas ettirilmemelidir.
C (Corrosive): Korozif
Canlı Dokuyu tahrip eden ya da demiri aşındıran/paslandıran
maddelerdir (R34, R35). Deriye ve göze hasar verirler. Gözleri ve
deriyi korumak için özel önlemler alınmalı, koruyucu giysi
giyilmeli ve buharı solunmamalıdır.
9
T (Toxic): Zehirli
T+ (Very Toxic-): Çok Zehirli
Zehirli (R23-R-25) ve çok zehirlidirler (R26-R28). Ağız, deri ve
solunum yolu ile zehirlenmelere yol açar. Vücut ile temas
ettirilmemelidir. Kanser riski taşırlar.
Xi (Irritant): Tahriş edici, rahatsız edici
Xn (Sensitising): Hassasiyet yaratıcı
Deriye ve göze hasar verirler (R20-R22i R36-R38). Buharı
solunmamalıdır. Vücut ile temas ettirilmemelidir. Gözleri ve deriyi
korumak için özel önlemler almak gerekir. Koruyucu giysi
giyilmelidir. Ozon tabakasına zarar verirler.
H (Healt effect): Sağlık etkisi
İnsan sağlığına, kısa veya uzun dönemli hasar verebilirler (R40,
R45-R47). Vücut/cilt ile temas ettirilmemeli, ağız yoluyla
alınmamalı ve solunmamalıdır. Kanser riski taşırlar.
N (Toxic to environment): Ekotoksik
Sudaki ve doğadaki canlılara zarar verirler. Doğaya dökülmemeli
ve salınmamalıdırlar.
10
LABORATORY EQUIPMENTS
11
12
13
14
15
EXPERIMENT 9: INVESTIGATION OF THE PRINCIPLE OF VOLTA
BATTERY
9.1 PURPOSE
To investigate the structure and properties of the Volta battery.
9.2 THEORY
A zinc anode and copper cathode battery type that's created in an acidic solution is
called galvanic volta cell. Electron flow occurs from the anode to the cathode. Events that
take place here are shown in detail in (Fig 9.1). The electrical energy derived from the system
can be used to light a bulb. In this experiment, electrical energy will be obtained as a result of
spontaneous chemical reaction.
Fig. 9.1 The princible of Volta Batery
9.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Beaker
LED bulb (2.5 V)
Heard cable
Sulfuric acid (conc.)
Pure water
Sandpaper
Copper plates
Zinc plates
9.4 SET UP AND PROCEDURE
"Galvanic cell test" experiment which is designed in relation to the Fig. 9.2.
16
Fig. 9.2 Galvanic cell test
1. Clean Copper and zinc electrodes, washed with water and dried.
2. Fill 25 ml of tap water into 100 ml beaker and add 5-10 drops of concentrated sulfuric
acid solution then mix.
3. Set up copper and zinc electrodes into the solution
4. Make electrodes and bulb connections.
In the result of the experiment; observe whether bulp lightened or not, by electric
energy obtained from spontaneous chemical reaction and note your observations into your lab
notebook.
17
EXPERIMENT 10: ELECTROLYSIS OF WATER
10.1 PURPOSE
In this experiment, the electrolysis of water will be carried out and water will be
decomposed into H2 and O2 by electric energy.
10.2 THEORY
Electrochemical cells that produce chemical reactions from non-spontaneously
occurring chemical reaction, by giving external electric energy call electrolysis cell. In an
electrolysis cell, the two conducting electrodes immersed in an electrolyte solution and
current / voltage source is connected to tip of electrodes remaining above the solution. Anode
is electrode connected to the positive terminal of the current /voltage source and cathode is the
electrode which connected to the negative part. In order to get electrolysis occurs; a
corresponding voltage difference (higer then total of anode and cathode equilibrium voltages)
is applied between the electrodes. Directions of ions inside cell depends on sign of charge
they carry. While positively charges ions move toward negative electrode (cathode),
negatively charged ions move toward to positive electrode (anode). Electrons required for
reduction reactions are supplied from current/voltages source. Some of applications of the
electrolytic cell, can be summarized as; the purification of metals (copper, silver, aluminum
etc.), coating of various metal surface, silver, nickel or chromium, polishing metals, purify
metals from oils as cathode or anode, synthesis of Cl2 gas, obtaining H2 and O2 from water
decomposition, charge of batteries containing lead sulphate, separation of organic tissues for
medicinal purposes.
The relationship between chemical reactions and electrical energy is described by
Michael Faraday in the early 19th century. Faraday, has observed that the amount of reactants
is proportional to the amount of current and electrons passing from system during electrolysis.
Electrical charge which is carried by 1 mole (as Avogadro's number, 6,02x1023) electron
is called the Faraday constant and shown as F.
18
Fig. 10.1 Experimental design
N=
Q
nF
Q=It
m
Q
=
𝑀𝑊 nF
Here:
m: the amount of matter collected in the electrolysis,
MW: The molar mass of material collected in electrolysis
I: Current (Amps)
t: Time (in seconds)
n = Number of electrons transferred per mole.
m
𝐼𝑡
=
𝑀𝑊 nF
10.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Voltage-current source
Burette
Clamps
Sports
Crocodile tipped connection cables
Steel (or platinum) electrodes
Beaker
Puar
H2SO4 solution
10.4. SET UP AND PROCEDURE
The experiment is designed according to the Fig. 10.1
19
Fig. 10.2 Experimental design of water electrolysis
1. Take 14 mL of concentrated sulfuric acid and complete to 250 mL with distilled water. Add
250 mL H2SO4 solution into 500 mL beaker.
2. Attach two burettes upside down to the sports by clamps and immerse in to your acidic
solution. Pull up acidic solution a certain level into burette by using puar which fitted to tip of
burette, close burette tap and remove puar. Repeat same procedure to other burette.
3. Put tip of electrodes into tubes. Connect electrode outside part to the direct current output
of current/voltage source with crocodile pointed cables.
4. The current is set to be about 300 mA and is applied for 2 minutes.
5. Note that observed change and amount.
10.5. REPORT
Determine the nature and the quantities of the gazes in the burettes.
20
EXPERIMENT 11: DETERMINATION OF REACTION ENTHALPY
11.1 PURPOSE
To investigate the heat changes during the chemical and physical events.
11.2 THEORY
Thermochemistry is concerned with chemical phenomena accompanying changes in
heat. The amount of heat exchanged with the surroundings is an important property of a
chemical reaction. The amount of heat absorbed or released during a reaction under constant
pressure is called "enthalpy" and is represented by the variable H. When the pressure of the
systemis constant, the enthalpy change of a system equals to the heat exchanged with the
surroundings:
H=q
If a reaction gives heat to its environment, that reaction is exothermic and enthalpy
change (ΔH) is negative. If a reaction receives heat from its environment, that reaction is
endothermic and enthalpy change (ΔH) is positive. Reaction enthalpy divided into the
following classes in more detail:
Formation enthalpy is the enthalpy change during the formation of one mole substance
from its elements in standard conditions.
Enthalpy of combustion is the enthalpy change during combustion of a substance in
the presence of oxygen.
Enthalpy of solution, vaporization, melting and sublimation is related with changes
of state of matter or related with dissociations of molecules and ions.
Enthalpy of neutralization is the heat released during the acid-base reactions which
gives one mole water.
Temperature measurements can be done by a chemical reaction of the glass calorimeter
in the following figure. The reactants are stirred in a container made of polyurethane foam
and the temperature change is measured. Polyurethane foam is a good thermal insulator, cup
and its content are considered in isolation.
The amount of heat given or received in chemical reactions can be calculated by the
following formula:
q= m.c.ΔT
21
In this formula m, mass of solution (g); c, specific heat (cal/g.°C or J/g°C); ΔT,
temperature change in solution (Tlast-Tfirst).
The heat received by calorimeter is calculated by the following formula:
qkal = heat capacity of calorimeter. ΔT
Calorimeter heat capacity is given as cal / °C or J / °C in order to allow more precise
measurements. In this experiment, firstly heat capacity of calorimeter will be predicted, and
enthalpy of neutralization will be determined next.
11.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Beaker
Calorimeter
Thermometer
2 pieces of Styrofoam coffee cup
HCl solution (30 ml, 2 M)
NaOH solution (30 ml, 2 M)
1 piece of ice cube
Pure water
11.4 SET UP AND PROCEDURE
The experiment is set up according to the Fig. 11.1
A) Determination of the Heat Capacity of Calorimeter
1. Add 50 ml of water to the calorimeter and measure the temperature 3 times at 30
second intervals.
2. Add 60-70 ml water to the beaker and heat it about 50°C.
3. Carefully move 50 ml of hot water from the heater and measure the temperature 3
times at 30 second intervals.
4. As soon as meauring the hot water’s temperature, place it in the calorimeter
containing cold water. After mixing it throughly, measure the temperature 3 times at 30
second intervals.
5. Calculate the heat capacity of the calorimeter.
22
Figure 11.1: Representation of coffe cup calorimeter.
23
B) Determining the Heat of Neutralization
1. Place the 30 ml 2 M HCl solution to the calorimeter and measure the teperature 3 or 4
times with 30 second intervals (thermometer should be dry and clean).
2. Place the 30 ml 2 M NaOH solution to the calorimeter and measure the teperature 3
or 4 times with 30 second intervals (thermometer should be dry and clean).
3. Add the NaOH solution to the calorimeter containing HCl solution and mix it with
thermometer and then measure teperature 4 times with 30 second intervals.
4. Calculate the neutralization heat for 1 mol water.
5. (The solution which is obtained after notralization, has density as 1.02 gr/ml and
specifi heat as 0.95 cal/gr.°C)
11.5 REPORT
A) Determination the Heat Capacity of Calorimeter
Temperature of Cold Water
Temperature of Hot Water
_____________
______________
_____________
______________
_____________
______________
Temperature of Mixture
_______________
_______________
_______________
Heat released from hot water: _________________________________cal
Heat received by cold water:
_________________________________cal
Heat received by calorimeter: _________________________________cal
Heat capacity of calorimeter: _______________________________cal/0C
B) Determining the Heat of Neutralization
Temperature of NaOH solution
___________
___________
Temperature of HCl solution
___________
___________
24
___________
___________
Temperature of Mixture
_______________
_______________
_______________
Heat received by solution______________________ cal
Heat received by calorimeter: ______________________ cal
Total heat released ______________________ cal
Number of moles of water ______________________ mol
Heat of Neutralization ______________________ cal/mol
25
EXPERIMENT 12: SOLID SOAP
12.1
To produce soap from animal or vegetable oil.
12.2 THEORY
Esters turn to carboxylic acid and alcohol by hydrolysis in acidic or basic medium.
Esterification and ester hydrolysis is an equilibrium reaction. Mainly alkaline catalyst is used
to shift the equilibrium to the hydrolysis. Wherein the carboxylic acid which forms salt by
reacting with base and help to shift the equilibrium towards hydrolysis.
Oils, glycerol esters are formed by high carbon fatty acids. These esters are generically
called glycerides and by the number of alcohol groups esterified with trialcohol glycerin
called as monoglycerides, diglycerides and triglycerides are called. Glycerides having
of the three identical fatty acid are defined simple glycerides and glcerides having different
fatty acids are defined as mixed glycerides. As example; tristearin is simple glyceride, αpalmito-α, β-diol is mixed glyceride. Mixed glycerides, glycerine 1,2,3 or α, β, γ or α, β, α
indicate which of the alcohol group esterified by which of the fatty acid (For example; αpalmito-α, β-diol and 1-palmito-2-oleo-3-stearin like). Usually straight chain and double
carbon number fatty acids found in natural glycerides. Sodium or potassium salts of
carboxylic acids which are resulting product of hydrolysis of fats and alkaly hydroxides,
defined as soap and this hydrolize process defined as saponification. Fatty acid sodium salts
are white soap,potassium salts are soft soap.
26
12.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Volumetric flask (100 ml)
Graduated cylinders (50 ml)
Beaker (100 ml) x 2
Short glass pipette
Glass Stirring Rod
Beaker (500 ml ve 1000 ml)
Spatula
washing bottle
Pipette bulbs
Magnetic stirrer with heating
Magnetic follower.
Sodium hydroxide
Animal or vegetable fat
Common salt
12.4 SET UP AND PROCEDURE
Solid (White) Soap
Take 30g of the any plant or animal oil, and saponify with 30 mL of 5M NaOH solution
as follows:
Heat 5 ml of 5M NaOH solution and 5 ml water. Add the oil on this heated NaOH
solution and after half an hour, add 10 ml of water and 10 ml of NaOH on the mixture.
Meanwhile, stirr often and heat gently to boiling. About after 2 hours, add remaining NaOH
solution and if needed add an amount of water prior to the addition of NaOH to compensate
for the evaporated water. After a further half hour, add 25 ml of water and continue boiling
until a homogeneous paste is obtained. Thereafter, add 200mL hot water with vigorous
stirring, which results a crude and clear paste. Finally saturate the paste with 10 gr common
salt at boiling temperature and left it overnight in the casts. After cooling, next morning the
solidified soap in cast is removed and the pulp adhered to the bottom of the cast is washed
with water.
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Figure 12.1: Solid (White) Soap.
12.5 REPORT
1. Describe the chemical reaction that takes place in the process of saponification. What
are the reactants? What are the products?
2. Why is the NaCl used in the soap making process?
3. How many grams of soap did you get at the end of the experiment?
4. Place a small amount of the soap in a test tube and mix the soap with water well.
Touch a few drops of the solution to both red and blue litmus paper. Record your
observations. What explanation can you give for the observed color changes of the litmus
paper?
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EXPERIMENT 13: LEAD IODIDE PRECIPITATION REACTION
13.1 PURPOSE
Study of precipitation reaction and to learn the general laboratory techniques (solving,
crystallization, filtration) used in chemistry laboratories.
13.2 THEORY
In precipitation reactions, solutions of the anions and cations are mixed and a solid called
precipitate is obtained as reaction product. Solid reactants and products used in chemical
reactions in general may need to be purified. Solving, cyristallization, and fitration are the
tecniques used for purification of solid substances.
Solving
Solving process is made by gradually adding the substance to be solved into the solvent.
after each addition the mixture is stirred with the aid of a stick and provided the substance to
be dissolved. If there are large pieces they are crushed and the mixture is heated for
dissolving if necessary. Glass container do not contact directly to the flame during heating.
Asbestos fiber used for this purpose. When working with organic and flammable solvents,
naked flame is very dangerous, therefore electrical heaters should be used if possible. If
there isn’t an electrical heater, a asbestos heating wire should be used necessarily over a low
flame and should be very carefull. Excessive boiling should be avoided during heating.
Crystallization
Crystallization is one of the purification methods. Crystallization based on the principles
of dissolution of a substance in a solvent that solubility of the substance is maximum in hot
and minimum in cold solvent. Therefore the choice of solvent in crystallization process is
very important.
Crystallization Technique
Prepare a hot saturated solution of the crystalline matter in a suitable solvent. This
solution was hot filtered into a clean flask with a preheated funnel. The purpose of this
filtration is to separate solid particles that are insoluble in hot solvent. The purpose of heating
the funnel is to prevent crystallization from saturated hot solution on cold funnel wall. Prior to
filtration funnel must be heated either in an oven or by exposure to a hot steam.
29
Saturated solution is filtered into the beaker and allowed to cool by covering the beaker
with watch glass. The cooling rate is one of the most important factors that affect the size of
the crystals. If large crystals are desired to be obtained cooling should be slow, and small
crystals are obtained by fast cooling. Ice bath can be used for rapid cooling.
In some cases, the crystallization agent may be separated as an oil. In such cases, the
solution is heated again to dissolve the oily substance again and leave to cool very slowly
without breaking. To ensure slow cooling, the area around the beaker may wraped with a
clean towel.
If the crystallization does not ocur even though the solution was thoroughly cooled, a
baguette is rubbed against the wall of the beaker for scratching operation, or a seed crystal
should be added to the solution. It should also be noted that it is difficult to crystallize from
the viscous solution which is concentrated by thoroughly evaporating. So to concentrate the
solution by excessive evaporation should be avoided.
After the formation of crystals they are separated by filtration through a funnel, the
crystals are washed with a small amount of a solvent which can not solve crytals in cold and
dried.
Filtration
The filtration process is applied in two ways:
a) Simple filtration
For this purpose, the filter paper is folded first in half after four, then upper part of filter
paper rounded with a scissors and, formed into cone shape by opening one of the plies. Paper
is placed on the funnel. Funnel is placed on an iron ring or a clay of the triangle, depending on
its diameter. After placing a clean beaker under the funnel, the mixture to be filtered is
poured in the center of the filter paper with the help of a drumstick. The filtered mixture
should never be filled to the higher level of 1 cm below the upper edge of the filter paper.
Pleated paper filter can also be used in the filtering process. Preparation of pleated filter
paper is as follows: Round filter paper before folding in half after four (Figure 13.1).
30
Figure 13.1 Preparation of Pleated Filter Paper
Then the fold is opened, 1 to 2 and 3 to 2 are overlaid and folded to form 4 and 5
corners. Then the sequence (1,5), (3,4), (1,4) and (3,5) are fitted to the corners and folds are
created manually pressing the sharp edges. After each folding in the opposite direction of their
pleated folds of filter paper is ready to use. (Figure 13.2)
Figure 13.2 Pleated Filter Paper
b) Filtering with Buchner Funnel
Buchner funnel with filter assembly is shown in Figure 13.3.
31
Figure 13.3 Filtering with Buchner Funnel
Filter paper which is cut in suitable diameter is placed in a Buchner funnel as shown in
Figure 13.3 and vacuum is applied to the system by opening the sink faucet. Meanwhile an
amount of distilled water is poured onto the filter paper and the paper is firmly adhered to the
funnel. Then the mixture be aligned with the cone by means of a drumstick is poured slowly.
After the entire mixture transferred into funnel, the crystals on the filter paper are washed and
dried with the paper based upon the watch glass.
Reaction Equation:
Pb(NO3)2 + 2KI → Pbl2 + 2KNO3
32
13.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Beaker (100 ml) x 2
Glass funnel (big)
Graduated cylinders(25 ml)
Watch glass
Beaker (500 ml) x 2
Balance
Spatula
Magnetic stirrer with heating
Magnetic follower
Filtering paper
washing bottle
ring holder.
Lead Nitrate
Potassium Iodide
13.4 SET UP AND PROCEDURE
Put 1 g of lead nitrate in about 20 ml of water in a beaker; dissolve approximately 1 g of
potassium iodide in 20 ml water in another beaker and mix these two solutions. Add 300 mL
of water to the solution until the yellow precipitate dissolved and heat. Since a large amount
of water is necessary, large beaker should be used fort he reaction . Filter the boiling solution
on funnel with a pleated filter paper into another beaker. Before filtering process the funnel
must be heated by holding to vapor. Crystallize the collected filtrates by cooling in ice. Dry
filtered crystals. Crystals are yellow colored and hexagonal shaped. Insoluble in alcohol. The
solubility in water is 0.063 g / 100 ml. at 20 °C.
Fig. 13.4 Yellow Precipitate, Pbl2
33
13.5 REPORT
The mass of Pb(NO3)2 ____________________________
The mass of KI ____________________________
The mass of filtering paper ____________________________
Filter paper + product mass ____________________________
Product mass ____________________________
Calculations
Number of moles of Pb(NO3)2
Number of moles of KI
Name and number of moles of excess
reactant
Number of moles of the product (obtained)
Number of moles of the product (theoretical)
%Yield
34
EXPERIMENT 14: SEPARATION OF MIXTURES OF LIQUIDS BY
DISTILLATION
14.1 PURPOSE
Separation and purification of compounds in a mixture.
14.2 THEORY
Distillation is one of the most common method used for the purification and separation
of organic compounds. Distillation is carried out by the evaporation of liquids by heating and
re-condensation of the vapour into liquid again. Common distillation types can be listed as:
Simple distillation
It is applied on the compounds which do not decompose on or around the boiling
temperatures.
Vacuum distillation
It is used for the compounds which can decompose near or under the boiling
temperatures.
Steam distillation
It is used for the separation of compounds from non-volatile mixtures which are not
soluble in water.
Fractional distillation
It is applied on liquids which have close boiling points.
35
14.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Round bottom flask ( 500 ml)
Round bottom flask or erlenmayer (250
ml x 4)
Bunsen burner or magnetic stirrer heater
Distillation adaptor ( x 2)
Termometer
Condenser
Ice- water bath
Ethanol (C2H5OH)
Water
Hexane (C6H14)
Dichlorometane (CH2Cl2)
14.4 SET UP AND PROCEDURE
Fig. 14.1 Experimental design
1. Heat the liquid slowly, the temperature rises up and it stays constant when it reaches
to boiling temperature.
2. The distillate collected up to that temperature is taken away, called frontier and
another flask is placed to collect the main distillate.
3. The dropping speed should be as one or two drops per second while heating.
4. During heating, the thermometer should be checked continuously. The pure distillate
should be collected around the boiling point.
5. If the temperature of the mixture exceeds the boiling temperature, another fraction
can be collected. Remember that these two extra fractions may have the target compound.
Another distillation can be applied later.
36
14.5 QUESTIONS
1. How many fractions did you get?
2. Write the distillation temperatures of the fractions you collected and predict what kind
of liquids exist the mixture have.
37
EXPERIMENT 15: SYNTHESIS OF NYLON 6,6
15.1 PURPOSE
Study of polimerization techniques
15.2 THEORY
Polymers are macromolecules built from smaller molecular subunits, called monomers.
Synthetic polymers can be classified into two main types according to the mechanism by
which they synthetically grow from monomer to polymer: chain-growth polymers and stepgrowth polymers. This classification scheme is an update from historical nomenclature, in
which polymers were classified by whether there existed a by-product of the polymerization
reaction (condensation polymerization) or not (addition polymerization). In a step-growth
reaction, the growing polymer chains (of any molecular length) may react with each other to
form longer polymer chains. The monomer or dimer may react in just the same way as a
polymer containing hundreds of monomer units. In chain-growth polymerization, however,
only monomers may react with growing polymer chains. That is, two growing polymer chains
cannot join together as in the case during step-growth polymerization.
In this reaction, monomers need not necessarily add sequentially, but instead small
polymer chains may couple into larger chains. For example, nylon 6,6 is an aliphatic
polyamide that is synthesized using A-A/B-B step-growth condensation-polymerization. The
two monomers involved in this polymerization are hexamethylenediamine and adipoyl
chloride, each of which is bifuctional (i.e., two ends of each are reactive), and each end
contains the same functionality (i.e., A or B functional groups).
The first step in the reaction is occurred
between one
molecule of
hexamethylenediamine and one molecule of adipoyl chloride. The hydrogen atom of the
amine group belonging to hexamethylenediamine forms a hydrochloric acid (HCl) molecule
with the chloride from the acid functional group. The remaining adipoyl chloride molecule
and the hexamethylenediamine molecule will join together to form a larger molecule
(polymer). The molecule formed has an acid group at one end and an amine group at the other
and is a nylon 6,6 unit. The end groups can then react in a similar manner with other
acid/amine groups present on adipoyl chloride and hexamethylenediamine. After completion
of many steps of this process, the nylon 6,6 polymer will form.
38
Figure 15.1 Synthesis of Nylon 6,6
15.3 MATERIALS AND CHEMICALS
MATERIALS
CHEMICALS
Beaker (250 ml x 2)
Magnetic stirrer
Magnetic stir bar (x 2)
Stirring rod (glass)
Graduated cylinder
1,6-Diaminohexane (1g) H2N(CH2)6NH2
Adipoyl chloride (1mL) C6H8Cl2O2
Hexane (25mL) C6H14
NaOH ( or Na2CO3) 0.5g
Distilled water
15.4 SET UP AND PROCEDURE
Fig. 15.1 Experimental design
1. Weigh 1g of 1,6 diaminohexane in a beaker and add 25 ml of distilled water.
2. Heat the solution to dissolve all compound using magnetic stirrer.
39
3. Add 0.1 g of Na2CO3 (10-15 drops of 10 % Na2CO3 solution) to the solution.
4. In another beaker, dissolve 1 ml adipoyl chloride in 19 ml n-hexane, and pour this
into first solution.
5. You will notice an interphase between these two solutions. This film is removed out
of the beaker carefully with a glass rod and nylon 6,6 polymer is obtained.
15.5 QUESTIONS
1. What can you say about the molecular weight of the polymer you synthesized?
2. What is the reason of adding base to the reaction medium?
3. What do the two numbers correspond to in the name “Nylon-6,6?” What would the
chemical structure of the repeat unit be in “Nylon-2,2?”
40
41
DENEY 16: MOLECULAR WEIGHT DETERMINATION USING
FREEZING POINT DEPRESSION
16.1 PURPOSE
Freezing point determination and molecular weight determination of a solute from the
freezing point depression of solvent. Determination of molecular weight of suphur from the
freezing point depression of naphtalene.
16.2 THEORY
When a pure solid is heated, temperature of the solid increases until melting point of
the solid is reached. Temperature stays constant during the melting of all solid since the heat
is used for melting of solid. Temperature starts to increase after melting of solid (turning into
liquid) is completed. Teperature increases of solid and liquid states are different, since heat
capacities of solid and liquid states are not same. As it can be seen in temperature-time graph
(Figure 16.1) below liquid starts to turn into solid at temperature T1 and the temperature
remains constant during this turning period (time t1 - t2).
Şekil 16.1 Temperature - time graph (cooling curve).
During freezing, as the particles pass from liquid to solid, they enter a certain geometric
sheen and the potential energy of the material begins to fall. For this reason, the formation of
solid particles during freezing forms heat energy, and this energy that meets the heat energy
42
dissipated by cooling. As a result, the temperature remains constant until the freezing is
complete. This helps us determine the freezing point of the naphthalene in the experiment.
The melting point of a substance is the temperature at which the liquid is equilibrated
together. For example, at 1 atm pressure, ice melts at 0 ° C. During melting period solids
become irregular and transfer into liquid from a regular and certain crystal structure. The
amount of heat required to melt one mole of a solid is called molar melting heat. The heat
given after the melting point will increase the average kinetic energy of the liquid molecules
and the temperature of the liquid will increase. This state continues until the boiling point and
stops at the boiling point. Because the heat given at the boiling point is spent for boiling rather
than raising the temperature of the liquid. The temperature at which the vapor pressure of a
liquid is equal to the atmospheric pressure is called boiling point. At this temperature the
liquid starts to boil. The boiling liquid evaporates and over time the whole liquid becomes
vapor. The subsequent heat is used to increase the kinetic energy of the vapor molecules. The
amount of heat required to evaporate one mole of liquid is called the molar evaporation
temperature. A curve is called as heating curve that shows changes in temperature with time
when materials are heated. A curve that shows changes in temperature with time when
materials are cooled is called a cooling curve. The temperature (condensation temperature) at
which the gas is converted into liquid is the same as the temperature at which the liquid is
converted into the liquid (boiling point). In the similar case, the temperature (freezing point)
at which the liquid turns into solid is the same as the temperature at which the liquid turns into
liquid (melting point). It is known that, compared to pure solvents, the total vapor pressure of
unvolatile solutions of these solvents is lower. The decrease in vapor pressure in such
solutions, causes the boiling point to rise and the freezing point to decrease. Such properties
of solutions are called "colligative properties".
Colligative properties are numerical properties that are not dependent on the structure and
chemical properties of the material but only on the structure of the molecule. These are
vapor pressure descent, freezing point descent, boiling point elevation and osmotic press. The
colligative properties vary depending on the solute / solvent particle ratio in the solution. In
general, the addition of a solute raises the boiling point of the solvent while reducing the
freezing point. The descent of the freezing point for a given solvent is directly proportional to
the concentration of the solute present in the solvent.
T = Kd ×m
T = Freezing point depression
Kd = Freezing point depression constant of solvent
43
m = molality
Molality: number of moles of the substances in 1000g of solvent.
Molality = number moles of solute, n/ 1000 g solvent
Measurements related to freezing point depression can be used to determine the molecular
weights of substances as in the case of boiling point elevation. A certain amount of unknown
molecular weight substance is dissolved in a freezing point depression constant known
solvent. Freezing point of the solution is determined. Freezing point depression and molality
of the solution are determined.
In this experiment naphtalene is solvent and suphur is solute. If one mole of suphur is
dissolved in 1000 grams of naphtalene, freezing point of the solvent 6,9°C decreases (Kd =
6.9°C/molal). A known amount of sulphur will be dissolve in a known amount of naphtalene
and molecular weight of sulphur will be determined.
16.3 CHEMICALS AND MATERIALS
Materials
Chemicals
400 ml beaker
Naphtalene
Two holed cork
Sulphur
Test tube
Magnetic stirrer
100 0C ( 0,1 0C scaled)
thermometer
16.4 SET UP AND PROCEDURE
Construct the experimental set up shown below. Place the thermometer in the hole of two
holed cork. Wrap the thermometer and the cork with a towel while turning the thermometer
slowly while inserting to the hole. Make sure above 70°C of thermometer scala can be seen
and tip of the thermometer does not touch to the bottom ( otherwise it could be broken) .
Weigh 5 g of Naphtalene and record amount as solvent weight, m2. Make sure the test tube is
clean and dry before filling. Pour all naphtalene in thr bottom of a big test tube. Cover the
tube with the two holed cork with thermometer anda wire stirrer placed. Place the tube in a
44
beaker containing water. Heat the beaker slowly untill naphtelene completely melts. Melting
point is observed around 80°C. Take the bunsen burner under the beaker and put it off.
Record the temperature at every 30 second while stirring continuously. Continue this
procedure till teperature drops to 75°C. Weigh 1 g of suplphur ( record the weighted amount
as solute weight, m1) and add on the cooled solid naphtalene. Place the thermometer and
stirrer and heat in a water bath untill naphtalene and suphur melt completely. After turning the
bunsen burner off and record the temperature drop at every 30 second in the 85-70°C range.
Experiment is completed. Make your calculations using your experimental data.
To clean the the test tube heat in water bath once more until all contents melt. When every
thing the Take the thermometer and stirrer out after contents of the test tube completely
melted. Empty the melted naphtalene in the naphtalene labeled beaker. Never pour the melted
naphtalene in the sink.
16.5. RESULTS AND DISCUSSION
1. Draw the cooling curves for Pure Naphtalene and suphur-naphtalene solution on a graph
paper.
Naphtalene (solvent ) weight (m2)
………………………………………
Cooling curve data of pure Naphtalene
t (time, s)
………………
………………
………………
………………
………………
………………
………………
………………
………………
T (temperature, °C)
…………………
…………………
…………………
…………………
…………………
…………………
…………………
…………………
…………………
Suphur (solute) weight(m1)
t (time, s)
………………
………………
………………
………………
………………
………………
………………
………………
………………
T (temperature, °C)
…………………
…………………
…………………
…………………
…………………
…………………
…………………
…………………
…………………
………………………………………
Cooling curve data of Suphur solution in Naphtalene
t (time, s)
………………
………………
………………
………………
………………
………………
………………
T (temperature, °C)
…………………
…………………
…………………
…………………
…………………
…………………
…………………
t (time, s)
………………
………………
………………
………………
………………
………………
………………
T (temperature, °C)
…………………
…………………
…………………
…………………
…………………
…………………
…………………
45
………………
………………
…………………
…………………
………………
………………
…………………
…………………
2. Determine the freezing points from the cooling curves.
Freezing point of püre Naphtalene (T1)
………………………………………………
Freezing poiny of the solution (T2)
………………………………………………
3. Kd ( Naphtalene) is 6,9° C/molal. Calculate the molality of the solution.
Freezing point depression (T)
Molality of the solution (m)
………………………………………………
………………………………………………
4.Calculate the molecular weight of sulphur using Molality (m), m1 ve m2 data.
Molecular weight of sulphur (MW)
………………………………………………
5. Atomic mass of suphur is 32 g/mol. write the molecular formula of suphur as Sn using the
molecular weight value you found
Sn ………………………………………………
6. Look at the correct molecular formula of sulphur in your book. Calculate the theoretical
molecular weight of suphur and percentage error of your experiment.
% Error in MW ………………………………………………
16.6. QUESTIONS
1. What is the percentage error in the freezing point value of Naphtalene?
2. What is the advantage of using your experimental freezing point value for Naphtelene
in the determination of the molecular weight of suphur?
46