Solutions
A solution is a mixture that has no visible
boundaries among its components
(i.e. a homogeneous mixture)
Vinegar:
water + acetic acid (+ others)
Brass:
copper + zinc
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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http://www.ehow.com/about_6369891_brass-alloy-information.html
The components of a solution may either be
solid, liquid, or gas
Component Component
1
2
Resulting
solution
example
gas
gas
gas
air
gas
liquid
liquid
gas
solid
solid
soda water
(CO2 in H2O)
H2 in palladium
liquid
liquid
liquid
ethanol in water
solid
liquid
liquid
sugar in water
solid
solid
solid
silver in gold
Brown, , E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd.
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
A solution contains a solvent and solute(s):
The solvent is present in larger amount, while the
solute(s) is/are present in smaller amount/s
Solution
soft solder (s)
softdrinks (l)
air (g)
Solvent
Solute
Pb
Sn
H2O
sugar, CO2, etc
N2
O2, Ar, etc
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
A molecular view of the
solution process
When salt is placed in a glass of water,
it dissolves
http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/health_tools/sore_throat_slideshow/photolibrary_photo_of_salt_sprinkled_into_water.jpg
When the solute dissolves in the solvent, particles
of the solute disperse throughout the solvent
solvent-solvent
interaction
solute-solute
interaction
solvent-solute
interaction
remember your IMFAs!
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
To determine if a solution will form, the three
types of interaction are considered
solvent-solvent
attraction
>
solution process
unfavorable
solute-solvent
attraction
&
solute-solute
attraction
<
solution process
favorable
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Effect of temperature on solubility
(water solvent, gas solute)
Solubility is the amount of solute that dissolves in
a fixed amount of solvent at a given temperature
i.e. solubility of NaCl at 100°C = 39.12 g/100 mL H2O
20.00 g NaCl
+
100 mL H2O
39.12 g NaCl
+
100 mL H2O
40.00 g NaCl
+
100 mL H2O
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Gas solubility in water decreases
with increasing temperature
• There are relatively weak IMFAs between
gas and water
• When temperature rises, the gas
molecules get enough energy to overcome
the weak IMFAs
• The gas molecules leave the solution
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
During many industrial processes, large amounts of
water are taken from a nearby river or lake, pumped
through the system to cool materials, and then returned
to the water body at a higher temperature
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
http://www.earthscienceworld.org/images/search/results.html?Keyword=Thermal%20Pollution#null
The reduced solubility of O2 gas in hot water has a
direct bearing on thermal pollution, which is the
heating of waterways to temperatures that are
harmful to its living inhabitants
• increase in water
temperature accelerates
fish’s metabolism
• fish’s need for oxygen
increases
• supply of oxygen
decreases
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
http://www.dec.ny.gov/animals/32847.html
Effect of pressure on solubility
(water solvent, gas solute)
Gas solubility in water increases
with increasing pressure
P1 at equilibrium
P2 is applied
P2 at equilibrium
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
Gas solubility in water increases
with increasing pressure
• At a given pressure, the same number of
gas molecules enter and leave the solution
(that is, the system is at equilibrium)
• If the pressure increases, gas particles
collide with the liquid surface more often
• More gas particles enter than leave the
solution per unit time, thereby increasing
the solubility of the gas
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
The effect of pressure on solubility is seen
when one opens a bottle of a carbonated
beverage (champagne, beer, or soft drinks)
• carbonated beverage is
bottled under a CO2 pressure
greater than atmospheric
pressure
• when the bottle is opened,
CO2 pressure above the
solution is decreases
• CO2 solubility decreases
• CO2 bubbles out of solution
Brown, , E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd.
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Expressing Concentration
Concentration is the amount of solute in a
given amount of solution.
- Percent (% w/w, %v/v)
- parts per million (ppm), parts per
billion (ppb), parts per trillion (ppt)
- Molarity (moles solute/L solution)
1. A typical aspirin tablet contains 300. mg of the
active ingredient, acetylsalicylic acid. What is
the average concentration, expressed as
percentage by weight (% w/w), of acetylsalicylic
acid in the body of a 165-pound person who
has just taken two aspirin tablets. Assume all of
the aspirin dissolves. 0.000790%
2. Iodized salt may be prepared by mixing in a
small amount of potassium iodide in table salt
(7.6 x 10-5 g of KI per gram of table salt). What
is the concentration of KI in iodized salt
expressed in ppm? 76 ppm
3. The maximum permitted level of mercury in
drinking water is 0.002 ppm. Analysis of 250.mL sample of tap water was found to contain
0.550 moles of Hg. Is this water supply safe for
human consumption? 4.41x104 ppm; NOT
SAFE
4. The Safe Drinking Water Act of 1974 (US) sets
a maximum of 160. mg of sodium per liter of
drinking water. What is the maximum molarity
of sodium chloride permitted in community
drinking water? 6.96x10-3 M
Dilution
Solutions may be labeled as dilute or
concentrated.
Dilute solutions have low concentrations of
solute while concentrated solutions have
higher concentrations.
In dilution, the amount (moles) of solute
DOES NOT change. Only the concentration
is decreased.
C1V1=C2V2
How would you prepare 15.5 L of 0.300 M
urea from 2.10 M urea?
M1V1 = M2V2
2.1M (V1) = 0.30M (15.5L)
V1 = 2.21 L
Take 2.21 L of 2.1 M urea, add enough
water to make 15.5 L of solution.
Acids and bases:
Properties and definition
We encounter acids in our daily lives
hydrochloric
acid
(HCl)
citric acid
(C6H8O7)
acetic acid
(CH3CO2H)
http://www.sunnysidecorp.com/images/Muriatic%20Acid.gif
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We encounter bases in our daily lives
sodium hydroxide
(NaOH)
ammonia
(NH3)
http://www.ultramega.com.ph/products-search.php?sub_cat_id=34
://www.pinegloproducts.com/catalog06/productscatalog/864oz/glass_ammoniacleaners/ammonia_lemon.gif
An acid is a substance that produces H+
when dissolved in water
HX
HCl
H2O
H2O
H+(aq) + X-(aq)
H+(aq) + Cl-(aq)
H2O
CH3CO2H
H+(aq) + CH3CO2-(aq)
Aqueous (or aq) is a solution wherein water is the
solvent
The double-headed arrow signifies that the reaction
goes forward and reverse
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
A base is a substance that produces OHwhen dissolved in water
MOH
NaOH
H2O
H2O
H2O
NH3
M+(aq) + OH-(aq)
Na+(aq) + OH-(aq)
NH4+(aq) + OH-(aq)
The double-headed arrow signifies that the reaction
goes forward and reverse
Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia
Pte. Ltd.
Acids and bases have the following properties
Acids
• taste sour
• aqueous acid
conducts
electricity
Bases
• taste bitter
• feel slippery
• aqueous base
conducts
electricity
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Ions cause aqueous solutions to be
good conductors
• to light the bulb, electric
current must flow between
the two wires
• ions carry electrical charge
from one wire to another,
thereby completing the
circuit
copper
wire
Acid-base reaction
(aka neutralization reaction)
An acid-base reaction is a reaction between
an acid and a base to form salt and water
acid + base  salt +
water
HCl + NaOH  NaCl + H2O
CH3CO2H + KOH  KCH3CO2 + H2O
salt is an ionic compound made of a cation other
than H+ and an anion other than OH- or O2Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
When vinegar reacts with baking soda,
water and carbon dioxide are produced
CH3CO2H + NaHCO3  NaCH3CO2 + H2CO3
H2CO3  H2O + CO2
How much carbon dioxide (in L) is produced when 5.00
g NaHCO3 reacts with 20.0 mL of 0.85 M vinegar at 25ºC
and 760. torr? 0.416 L
It is natural to have HCl in the stomach, but the
problem occurs when the amount of HCl is too high
in the blood plasma,
CO2 + H2O
H2CO3
by-product of
metabolism
H2CO3
H+ + HCO3-
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
To temporarily reduce the amount of HCl in the
stomach, an antacid may be taken. The HCl and
the antacid undergo an acid-base reaction
Kremil-S and Maalox
contain Al(OH)3 and Mg(OH)2
3HCl +Al(OH)3  AlCl3 + 3H2O
2HCl +Mg(OH)2  MgCl2 + 2H2O
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
http://www.unilab.com.ph/hcp/CMS_Files/kremilStablet_productshot1.jpg
http://www.maaloxus.com/assets/productImages/regularLiquid.jpg
Acid-base indicators
An indicator is a substance that is added to a
solution. It turns one color in an acidic medium
and turns another color in a basic medium
• litmus paper
• phenolphthalein
rown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte.
Litmus paper contains various organic
compounds. It changes color depending on the
acidity/basicity of a solution
red to blue: base
blue to red: acid
http://www.britannica.com/EBchecked/topic/343896/litmus
//oldwww.mtlsd.org/senior/science/JPtachcinski/Lab_Proc/Basic%20Science%20Lab%20Techniques_files/litmus.jpe
Phenolphthalein is colorless in acidic and neutral
solutions but reddish pink in basic solutions
OH
O
OH
C
O
C
OH
O
H
O
C
C
O
colorless
O
reddish
Chang, R. 2002. pink
Chemistry 7 ed. Singapore: McGraw-Hill.
Skoog, D., D. West, and F.J. Holler. 1996. Fundamentals of Analytical Chemistry 7 ed. USA: Saunders College Publishing.
th
th
pH
pH is a logarithmic scale that indicates the
amount of H+ in solution
pH = - log [H+]
where [H+] = concentration of H+ in units of molarity
= moles H+ / L of solution
An HCl solution has [H+] = 1.00 x 10-6 M.
Calculate for the pH of the solution
pH = - log [H+]
pH = - log [1.00 x 106]
= 6.00
pH values indicate if a solution is
acidic, neutral, or basic
• If pH < 7.00, solution is acidic
• If pH = 7.00, solution is neutral
• If pH > 7.00, solution is basic
pH of some familiar aqueous solutions
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
Honey, I told you
not to leave your
bike out in the rain!