Question

Assertion (A): Soap does not form lather with hard water.
Reason (R): Hard water contains salts of calcium and magnesium which react with soap to form insoluble substances (scum).

• A. Both A and R are true and R is the correct explanation of A.
• B. Both A and R are true but R is not the correct explanation of A.
• C. A is true but R is false.
• D. A is false but R is true.

Hint:

Hard water forms scum with soap due to calcium/magnesium ions, preventing lathering.

Answer 1

The Correct Option is A

Assertion (A): Soap does not form lather with hard water.

Reason (R): Hard water contains salts of calcium and magnesium which react with soap to form insoluble substances (scum).

In this problem, we need to determine the relationship between the assertion and reason given. Let us evaluate each statement:

• The assertion states that soap does not form lather with hard water. This is true because the presence of certain ions in hard water interferes with soap's ability to produce lather.
• The reason provided is that hard water contains salts of calcium and magnesium, which react with soap to form insoluble substances called scum. This explains why soap fails to lather in hard water, as these insoluble substances reduce the effectiveness of soap in interacting with water molecules to form lather.

Both the assertion and the reason are true. Moreover, the reason (R) provides a valid explanation for the assertion (A) because it identifies the chemical interaction between soap and the ions present in hard water as the cause of reduced lathering.

Therefore, the correct answer is: Both A and R are true and R is the correct explanation of A.