Which set of the following contains only true statements:
a. it is usually more convenient to measure δe than δh.
b.“hot packs” used by skiers and others for warmth are based on the crystallization of sodium acetate from a highly concentrated solution. the sign of δh for this crystallization is positive.
c. the work done when a system expands against a constant external pressure is assigned a negative sign.

option (c)

Explanation:

Option c is the correct i.e the statement given in the option c is true.

The above option is true because, when the external pressure is applied, the energy is being added to the system.Thus, the positive work is done. But when the system expands against that external pressure, the energy is being released i.e the being done is negative.

a cold ice-tea.

pour in room temperature or cold water. cover the pitcher and refrigerate. steep white or green tea for 6 to 8 hours; steep black or oolong tea for 8 to 12 hours.jun 28, 2015