Page 97 - Chemistry - XI

Q4. What is meant by foaming capacity of soap?
Ans. It is measured by the measuring length of the foam formed when soap solution is shaken for fi xed
number of times.

Q5. Give one example of soap.
Ans. Sodium stearate

PROJECT - 5

Introduction
Tea is commonly used in India. Tea is acidic in nature and colour of tea varies from sample to sample and
also it depends upon extent of boiling. If we take excess of tea, it may cause hyper acidity. Therefore, we
must know the acidity of diff erent samples of tea.

Objective

Study of acidity of diff erent samples of tea leaves and reasons for the variations in colour of tea prepared
from these leaves.

Materials Required
Samples of tea leaves, distilled water, M/50 NaOH, phenolphthalein

Principle/Theory
Tea contains weak tannic acid which can be estimated by titrating it with a strong base (NaOH) using
phenolphthalein as an indicator.

Procedure
1. Take 10 g of the sample of tea leaves and prepare the extract of each sample in 100 mL of distilled

water.
2. Take 10 mL of tea extract in a conical fl ask and dilute it with 10 mL of distilled water.
3. Shake the solution well and titrate it against M/50 NaOH solution using phenolphthalein as an indicator.
4. Titrate other tea samples, also.
5. You can take tea leaves in a burette if colour of tea creates problem and 20 mL of NaOH in a burette

and add phenolphthalein in NaOH.

End Point
Pink to colourless

Observations

S. No. Initial burette reading Final burette reading Volume of tea extract used
1.
2.

3.

4.
5.

95