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Project–B
1.
Purification and Characteristics of Chemical Substances
3.1
To determine the melting point of organic substance.
3.2
To determine the boiling point of organic substance.
3.3
To obtain Pure Substances by Crystallization Process.
(Alum, Copper Sulphate, Benzoic acid)
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3.1 Determination of the Melting Point of Oragnic Substances
Melting Point : The specific temperature of any
solid substance at which it melts completly is called
its melting point. The pure organic compound
always melt at specific temperature, it can be test
by its melting point. The melting point becomes
less by the presence of impurities.
4.
Now place the close end of capillary on
table and slowly strike capillary tube or
slowly by pen, coin etc. So that the
powder comes lower to the close end.
Repeat the above procedure 3-4 times so
that the capillary tube is filled with
powder upto 3-4 mm in height and there
Capillary tube
fine powdar
plate
to push
to strike
Fig 3.1 (A) To close the mouth of capillery tube.
(C)
(R)
Objective : To determine the melting point of
organic substance. (acetamide).
Apparatus : Beaker or Round bottom flask,
tripod stand, thermometer, spirit lamp or
bunsen burner, capillary tube, conc.
H 2SO4 etc.
Procedure :
(A) To, fill the capillary tube with given
substance :
1. Generally the melting point can be
determined with the help of capillary
tube. For this take a capillary tube of 5-6
cm long and of about 1mm of diameter.
Close one end of the capillary tube by
melting it over the flame of burner.
2.
3.
Take the some organic compound an a
plat and make a powdered substance by
grinding.
To fill this powder into capillary, push
this powder in it, So that some powder
will enter into the capillary.
will be no portion remain empty (no air is
present).
(B) To find the melting point of substance:
Thermometer
Capillary tube
burner
Fig 3.2 To find the melting point.
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1.
Adjust the apparatus according to the
Result : The melting point of given
figure. 3:2 Fill the 1/2 of beaker or Round
substance is 80°C.
bottom flask with water and put it on the
Procedure :
1. The open end of capillary tube should
tripod stand.
be placed on the upper side of liquid of
Note : When you have to find the melting point
beaker.
of the organic substance which is having
2. Take the liquid of that quantity which
lower than 1000C melting point then take
is sufficient to deep the bulb of
the water into beaker, but for the substance
thermometer and the bottom end of the
of having melting point more than 100°C
capillary. If you take more water then it
take oil or conc. H 2SO4 in beaker.
2.
will take more heat to heat it.
Wet the capillary tube with the liquid of
3. Stir the liquid of beaker continuously,
beaker and attached it with thermometer in
But after 60° – 65° C or before the
such a way that the solid substance of close
melting point of the substance, repeat
end of capillary always remains near to the
the stirring process.
bulb of thermometer. Tie the capillary tube
Table : Find the melting point of some organic substance
Substance
Phenol
Benzophenol
Nephthol
Melting point in 0C.
42.0
46.0
54.0
Substance
Acetamide
Oxalic acid
Benzoic
Melting point in 0C.
82.0
101.0
122.4
Nephthelein
80.0
Urea
132.0
with the thermometer by the thread.
3.
4.
4. The liquid of the beaker should be
Burn the beaker slowly in uniform way by
Gansparant and heat the substance upto
the burner and stirr the liquid.
melting point slowly.
Now note temperature at which the solid
5.
If the solid substance is attached to the
substance of capillary tube becomes in the
outside wall of capillary tube then
form of transparent liquid after melting. This
remove it with the help of filter paper.
is the melting point of solid.
6.
Place the thermometer vertically into the
Observation : The given substance is
beaker and place the eye at the point of
completely melts at t°C (80°).
mercury, while taking the reading.
3.2 Determination of Boiling Point of Organic
Boiling Point : When the liquid in heated its temp
is known as the boiling point of liquid than its vapour
slowly increases and after than there will be a
pressure will be equal to the atmospheric pressure.
stage when the whole water will boil than the
temperature remains constant. This temperature
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[A] Boiling point tube method :
Objective : To determine the boiling point of
the given organic substance (acetic acid).
Apparatus : Boiling tube of having two holes,
thermometer, burner, organic liquid whose boiling
point has to be determined, the pieces of
porcelein, tripod stand, sand bath.
Procedure :
1 When the liquid is present in large
quantity, take a boiling tube of hard glass.
Take a organic liquid of about 20-25 ml
into it whose boiling point has to
determined.
2. Pour some 3-4 pieces of porcelein into
the liquid of the tube so that the liquid
should not bump during burning.
3. Place one of the thermometer into the
hole of flask and fix the discharging tube
into the other hole and fit the cork on the
boiling tube.
4. Fix the boiling tube into the clamp of the
stand according to figure, place the bulb
of the thermometer at 1 cm high from the
liquid. Now to heat the boiling tube, heat
the sand bath by burner.
5. See the level of mercury of the
thermometer of testtube. The temperature
of thermometer increases slowly. After
sometime the liquid of the boiling tube
starts boiling and liquid Vapour comes
out from the discharge tube. At that stage,
temperature of thermometer becomes
constant. Note down the reading. This
will be the boiling point of liquid.
Observation : The boiling point of given liquid
(acetic acid) is 110°C
Precautions : according to the experiment 3.1
(B) Capillary tube Method :
Objective : To determine the boiling point of
organic liquid by capillary tube method.
Apparatus : Beaker, burning tube, small
boiling tube, Capillary tube, tripod stand,
Stirrer, water, oil of conc. H 2SO 4 if you want
to heat more than or ignition stirrer, stand,
burner wire gauze 100°C.
Procedure :
1. When the quantity of liquid is very less
than use above method. Take burning
Thermometer
vapour of liquid
boiling hide
liquid
Sand bath
Fig 3.3 To find the boiling pt. of liquid.
2.
3.
tube or small boiling tube and fill it with 2ml.
organic liquid.
Tie the burning tube with the
thermometer by thread or rubber ring.
Place the beaker on net wire of tripod
stand after filling it 1/2 with the oil conc
H 2SO4 according to the figure and put
the thermometer in perpendicular form
with the help of clamp of stand.
Thermometer
stirrer
Capillary tube
liquid
Bubbles
Substance
Fig 3.4 To find the boiling point with the help
of capillary tube method
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4.
The capillary tube of about 6cm long
whose bottom edge is placed on the
burning tube. Now heat the liquid
slowly and stirrer the liquid carefully.
When the bubbles from the bottom edge
of capillary coms out then note the
temperature of thermometer. It is the
boiling point of liquid.
Observation : The reading of thermometer is
t°C.
Result : The boiling point of given organic
substance in t°C.
Precaution :
1.
The thermometer should be placed
perpendicular in the beaker.
2.
Burning tube should be placed with the
thermometer and the thread is kept on
the liquid of beaker.
3.
Stir the liquid of beaker with the help
of stirrer.
4.
If the temperature of given organic
liquid is less than 100°C than take the
water into the beaker.
5.
3.3 To Obtain Pure Substance by Crystallization Process
Crystallization : When you cool the hot and
saturated solution of substance,it crystalizes,
this process is called crystallization.
Process of making crystal :
There are following terms include in the
process of crystallization.
1. To prepare solution : Take some distilled
water in beaker put some impure substance
in it gradually and continously stir it with the
help of glass rod. Try to dissolve the solid
by heating the beaker slowly. When some
solid is left at the bottom then stop stirring
and put some solid in it.
2.
glass rod
Solution
Wire gauze
Filtering : Filter the obtain solution and
Fig 3.6 To heat the solution.
glass rod
beaker
solution
Fig 3.5 Mixing with glass rod.
transfer it into the cup of porcelein with the
help of filter paper . Fold the filter paper
and fit it into the funnel.
Take a circular part of filter paper and fold
it from the bottom.
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according to the figure. Open the folded Paper
in such a way that 3 largers are in one side
and one large is on the other side. In this
situation the funnel shape is same as the cone.
Put it into the funnel and pour some drops of
water in it and mix it. So that the filter paper
stick with the wall of the funnel. Now in this
way the filtering process is completed.
3.
Concentration of saturated solution upto
Crystallization point : Now heat this cup
by putting it on the sand bath. After every
minute take some solution on the glass rod,
blow on it or move it in the air. When layers
of solid are forms on the glasses rod, stop
to heat it. The solution is concentrated , upto
the crystallization point.
Now put the cup open in the air or put it on
the beaker that filled with cold water. So
that the solution becomes cold.
Filterate
Fig 3.7 To fold the filter paper
and keeping the funnel.
Filtering process in shown with the help of
filter paper and funnel and the transformation
of solution into the cup of funnel shaped as
shown in the figure.
To evaporate the solution.
Soild residue
air blowing
To make the layer
solid
Fig 3.9 To test the crystallisation.
Funnel
4.
Porceline bowl
funnel
end filterate
Fig 3.8 To filter the solution and transfor.
To purify the mother solution and dry
the
crystals : When the crystallization is
completed then carefully purify the
mother solution and press, the crystals
between the pieces of filter paper to dry it.
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filter paper
Crystals
crystal
mother solution
Cold water
Experiment – 1
Objective : To determine the pure substance
(CuSO4 ) from the impure sample with the help
of crystallization
Principle : Filter the impure CuSO4 solution
in presence of dilute sulphuric acid and dissolve
less quantity of water in it. Now Vapourise the
solution upto crystallization point. After cooling
the solution, blue crystal of CuSO 4 .5H2O are
separated out.
4.
When the crystallization is complete then
remove the mother solution by
decantation. Carefully wash the crystals
of CuSO4 into the alcohol. Dry the
crystals by pressing them between filter
paper.
5.
Measure the dry and pure crystals of copper
sulphate
Result :
Apparatus : Beaker, China dish, rod, funnel,
sand bath.
1. found Crystals =
gm
2. Colour
=
Substance : Impure copper sulphate.
3. Shape
=
Method –
1. Grind the impure CuSO 4 properly. Take
6-7 gm impure CuSO4 into the beaker
and add less quantity of water in it. Add
some drops of dilute H2SO 4 into the
solution so that the hydrolysis of CuSO 4
is not possible, filter the solution and take
it on the china dish.
2.
3.
Blue
Precaution :
1.
Wash the impure CuSO4 in the presence
of less quantity of water.
2.
Don’t heat the solution for a long time
otherwise you will get a different
substance in place of crystal.
3.
Put the china dish on the sand bath and
start to heat it. Stop heating till we get
the crystallization point.
Use dilute H 2SO4 during preparation of
CuSO 4 solution otherwise there is
possibility of hydrolysis of CuSO 4 .
4.
Now put the china dish on the beaker for
cooling it. After sometime the crystals are
formed.
Slowly cool the conc. solution so that the
big crystal will form. If you cool it then
the crystal will become very small.
5.
Put the crystal between the filter paper.
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Experiment – 2
Objective : To obtain the pure substance by
impure sample of alum with the help of
crystallization method.
Principle : Filter the impure sample of alum in
presence of dilute sulphuric acid and dissolve less
quantity of water in it. Now vapourize the solution
upto the crystallization point. After cooling the
solution, the crystals of pure sample are
separated.
Apparatus : Beaker, China dish, glass rod,
funnel, sand bath, filter paper, impure sample
of alum.
Method –
1.
Grind the impure alum properly, take 67 gm. impure alum in the beaker and
dissolved in less quantity of water and.
Add some drops of dilute H 2SO4 in the
solution so that the water reduction of
alum is not possible, filter the solution
2.
3.
4.
5.
and take it into the china dish.
Put the china dish on the sand bath and
start to heat it ,stop heating when you
get the crystallization point.
Now put the china dish on the beaker
full of water and cool it. After sometime
the crystal are formed.
When the crystallization is completed
than filter the mother solution to remove
it carefully wash the crystals of alum
into the alcohal, dry the crystals by
pressing them between filter paper.
Measure the dry and pure crystals of
alum.
Result :
1.
Crystals found .................gm
2.
Colour = Colourless...............
3.
Shape = octahedral ..........................
Precaution :
●
Wash the impure alum in the presence of less quantity of water.
●
Don’t heat the solution for a long time otherwise you will get a specific substance in stead of
crystal..
●
Use dilute H 2SO4 during preparation of solution of alum. otherwise there is possibility of water
reduction of alum.
●
Slowly cool the conc. solution so that the big crystal formed.
●
Put the crystal between the filter paper for pressing.
Practice exercise
Q.1
Describe the melting point of a substance?
Q.2
What is the importance of melting point of a substance?
Q.3
What is the effect of impurities on melting point of any substance?
Q.4
To know the melting point of any substance, how do we select the medium of heating?
Q.5
To while determining the melting point of any substance, Why upper and of the capillary tube is
kept on the substance?
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Q.6
Define the boiling point of liquid?
Q.7
What is the definition of boiling point?
Q.8
What is the difference between melting point and freezing point of substance?
Q.9
What is the reason to cut the pieces of porcelin , during the determination of boiling point?
Q.10
How does the boiling point of liquid change by external pressure?
Q.11
When the capillary tube is used during the determination of boiling point of liquid?
Q.12
What is a crystal ?
Q.13
Why oil or sulphuric acid is added in impure copper sulphate during the process of
Crystallization?
Q.14
What do you mean by saturated solution?
Q.15
What do you understand by crysallisation point?
Q.16
Write down the formula of potash alum?
Q.17
What is the shape of crystal of alum?
Q.18
Explain crystal water?
(water of crystallization)