Question

Given below are two statements:

Statement (I): NaCl is added to the ice at 0°C, present in the ice cream box to prevent the melting of ice cream.

Statement (II): On addition of NaCl to ice at 0°C, there is a depression in freezing point.

In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are false
• B. Statement I is false but Statement II is true
• C. Statement I is true but Statement II is false
• D. Both Statement I and Statement II are true

Answer 1

Answer: (D)

Both Statement I and Statement II are true

Answer 2

Statement (I): NaCl is added to the ice at 0°C, present in the ice cream box to prevent the melting of ice cream. This statement describes a common practice. A mixture of ice and salt is used as a freezing mixture to create a temperature significantly below 0°C. Ice cream needs to be kept at a temperature below its freezing point (typically below 0°C) to remain frozen. By lowering the temperature of the surrounding environment using the ice-salt mixture, the melting of ice cream is prevented. Thus, Statement (I) is true.

Statement (II): On addition of NaCl to ice at 0°C, there is a depression in freezing point. When NaCl is added to ice at 0°C, some ice melts, forming liquid water. NaCl dissolves in this water, forming an aqueous solution of NaCl. The addition of a non-volatile solute like NaCl to a solvent (water) lowers the freezing point of the solvent. This phenomenon is known as freezing point depression, which is a colligative property. The freezing point of pure water is 0°C. The freezing point of an aqueous solution of NaCl is lower than 0°C. Thus, Statement (II) is true.

Both statements are factually correct.