Page 96 - Chemistry - XI

(b) To investigate the eff ect of addition of sodium carbonate on foaming capacity of diff erent
washing soaps.

Materials Required

Distilled water, hard water, Na CO and given sample of soap
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Procedure
1. Weigh 1 g of soap sample and put it into a beaker.
2. Add 50 mL of distilled water and dissolve the soap completely by gentle heating.

3. Prepare a solution of sodium carbonate in the other beaker by dissolving about 5 g of it in 50 mL of
distilled water.
4. Take three test tubes and number them 1, 2, 3. Place them in a test tube stand.
5. Pour 1 mL of the soap solution in each test tube.

6. Pour 10 mL of distilled water in test tube No. 1, 10 mL of hard water in test tube No. 2 and 5 mL of
hard water and 5 mL of Na CO solution in test tube No. 3.
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7. Determine the time taken for disappearance of foam produced in the three test tubes.
Observations

Amount of soap sample taken = _________ g
Volume of distilled water added = _________ mL
Volume of soap solution taken each time = _________ mL

S. No. Water used for foaming Time taken for disappearance

1. Distilled water

2. Hard water

3. 5 mL of hard water + 5 mL of Na CO 3
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Result

The foaming capacity of hard water is __________________ by additions of Na CO .
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Note: Hard water can be prepared by dissolving 2 g of CaCl or MgCl in 20 mL of distilled water.
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VIVA VOCE

Q1. What is soap chemically?
Ans. Soap is sodium or potassium salt of fatty acids.

Q2. How would you judge the quality of a soap?
Ans. It is done by measuring its foaming capacity.
Q3. How is the foaming capacity aff ected on addition of Na CO to soap? How is the foaming capacity aff ected on addition of Na
Q3.
Ans. It will increase.Ans. It will increase. 2 3

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