Page 95 - Chemistry - XI

Mg + Na CO → MgCO + 2Na +
2+
3
3
2
Thus, addition of sodium carbonate solution to the soap solution in water removes the Ca or Mg ions
2+
2+
which hinders the formation of foam and thus, increases the foaming capacity of soap.
Objective
To investigate the foaming capacity of diff erent washing soaps and the eff ect of addition of sodium

carbonate on them.
(a) To investigate the foaming capacity of diff erent washing soaps.

Materials Required
Four test tubes, four beakers (250 mL), glass rod, test tube stand, tripod stand, stop watch, 25 mL graduated
cylinder, four soaps, and distilled water

Procedure

1. Weigh 1 g each sample of soap in each beaker and number them as 1, 2, 3, 4, 5 and 6 respectively.
2. Now add 50 mL of distilled water in each beaker. Dissolve the soap in it.
3. Place six test tubes numbered 1, 2, 3, 4, 5 and 6 in a test tube stand.

4. Pour 1 mL of the soap solution prepared above in the test tube of corresponding number l, 2, 3, 4, 5 and
6 respectively and add 10 mL of water in each test tube.
5. Take one test tube. Place your thumb on its mouth and shake it upside down and vice-versa for
2 minutes. Foam will be produced. Keep the test tube in the stand and immediately start a stop watch.
Note the time taken for disappearance of foam.
6. Similarly, determine the time taken for disappearance of foam produced in other test tubes, also. Shake
every test tube in a similar fashion for equal number of time.

Observations
Amount of each soap sample taken = _________ g
Volume of distilled water added = _________ mL
Volume of each soap solution taken = _________ mL
Volume of distilled water added to the solution = _________ mL

Number of times each tube shaken _________

Soap sample No. Time taken for disappearance of foam
1.

2.
3.

4.
5.

6.

Result
The foaming capacity of diff erent samples are in the given order.

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