Assertion: Soft water lathers with soap but not hard water. Reason: Hard water reacts with soap to form insoluble salts which form scum, not lather.

Question

Assertion: Soft water lathers with soap but not hard water. Reason: Hard water reacts with soap to form insoluble salts which form scum, not lather. (A) If both assertion and reason are true and reason is the correct explanation of assertion. (B) If both assertion and reason are true but reason is not the correct explanation of assertion. (C) If assertion is true but reason is false. (D) If both assertion and reason are false.

Tardigrade Admin · Accepted Answer

Hard water contains calcium and magnesium salts which react with soap containing sodium stearate

(C_{17} H_{35} COON a)

to precipitate out

C a / M g

stearate.

2 RCOON a + C a^{2 +} \to (RCOO)_{2} C a + 2 N a^{+}

2 RCOON a + M g^{2 +} \to (RCOO)_{2} M g + 2 N a^{+}

Q. Assertion: Soft water lathers with soap but not hard water. Reason : Hard water reacts with soap to form insoluble salts which form scum, not lather.

If both assertion and reason are true and reason is the correct explanation of assertion.

If both assertion and reason are true but reason is not the correct explanation of assertion.

If assertion is true but reason is false.

If both assertion and reason are false.

Hard water contains calcium and magnesium salts which react with soap containing sodium stearate (C17​H35​COONa) to precipitate out Ca/Mg stearate. 2RCOONa+Ca2+→(RCOO)2​Ca+2Na+ 2RCOONa+Mg2+→(RCOO)2​Mg+2Na+

Q. Assertion: Soft water lathers with soap but not hard water.
Reason : Hard water reacts with soap to form insoluble salts which form scum, not lather.

Hard water contains calcium and magnesium salts which react with soap containing sodium stearate $(C_{17} H_{35} COON a)$ to precipitate out $C a / M g$ stearate.
$2 RCOON a + C a^{2 +} \to (RCOO)_{2} C a + 2 N a^{+}$
$2 RCOON a + M g^{2 +} \to (RCOO)_{2} M g + 2 N a^{+}$