Chemistry, asked by sahoomanisha4022, 11 months ago

(a) Explain the process of preparation of soap in laboratory.
(b) Why is common salt (sodium chloride) added during the preparation of soap?
(c) Why is soap not suitable for washing clothes when the water is hard?

Answers

Answered by dakshikumu
0

Explanation: a) the process of preparation of soap:

Take 25 ml of coconut oil in a measuring cylinder and pour it into a 250 ml glass beaker.

Measure 30 ml of 20% NaOH solution in another measuring cylinder and add it into the beaker containing vegetable oil.

Vigorously stir the mixture using a glass rod.

Touch the beaker from outside.  It is observed that the beaker is warm.

Place the beaker on a wire gauze placed over a tripod stand.

Heat the beaker using a Bunsen burner till the mixture become a whitish paste.

Remove the beaker from the flame and allow it to cool.

Dip a red litmus paper in the suspension formed.

When dipped in the suspension, the red litmus paper changes its colour to blue.

Dip a blue litmus paper in the suspension.

The colour of blue litmus paper remains the same.

To the above suspension, add 15g of common salt and stir it well with a glass rod.

After adding common salt, soap in the suspension gets precipitated out as solid.

Take a filter funnel and place a filter paper in it and fix it in a stand.

Place a beaker below the funnel.

Pour the contents of the beaker into the funnel over a glass rod and filter the contents of the beaker.

After filtration, soap is left behind in the filter paper.

Transfer the soap into another filter paper using a spatula and dry it by pressing with another filter paper.

Then, cut it into desired shape with a knife.

b) Common salt is added to precipitate out all the soap from the aqueous solution. Adding of common salt to soap solution decreases the solubility of soap due to which all the soap precipitates out from the solution in the solid form. This process is called salting out of soap.

c)soaps are not suitable for washing clothes when water is hard: Soaps, when used with hard water, does not lather or produce foam easily because of the formation of a curdy precipitate or scum. This scum is created when soaps react with the calcium and magnesium ions present in hard water.

Answered by dk6060805
0

Calcium & Magnesium are Components of Hard Water

Explanation:

a.) Following 5 steps are used in the preparation of soap in the laboratory:

1) Take about 20 ml of vegetable oil in a beaker.

2) Then, add 30 ml of 20% sodium hydroxide solution to it.

3) This mixture is heated slowly till it boils.

4) Then add 5 to 10 grams of sodium chloride (common salt).

5) Stir the mixture well and allow it to cool. On cooling the solution, solid soap separates out. 6. When the soap sets, it can be cut into pieces called 'soap bars'.

This process of soap preparation is known as saponification.

b.) In order to solidify and precipitate the soap from a solution we can add Salt.

c.) Soap does not work properly when hard water is used. calcium & magnesium are components of Hard Water. When soap is added with hard water, a large amount of soap in water reacts with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum. This makes the cleaning of clothes difficult.

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