The entropy change can be calculated by using the expression . When water freezes in a glass beaker, the correct statement among the following is:
1. | ∆ S (system) decreases but ∆ S (surroundings) remains the same. |
2. | ∆ S (system) increases but ∆ S (surroundings) decreases. |
3. | ∆ S (system) decreases but ∆ S (surroundings) increases. |
4. | ∆ S (system) decreases but ∆ S (surroundings) also decreases. |
Based on the reactions, ascertain the valid algebraic relationship:
1. | x = y | 2. | x = 2y |
3. | x > y | 4. | x < y |
The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound is-
1. | Generally negative | 2. | Always positive |
3. | Zero | 4. | Never negative |
The enthalpy of sublimation of a substance is equal to:
1. Enthalpy of fusion + Enthalpy of vaporization
2. Enthalpy of fusion
3. Enthalpy of vaporization
4. Twice the enthalpy of vaporization
Which of the following is not correct?
1. is zero for a reversible reaction.
2. is positive for a spontaneous reaction.
3. is negative for a spontaneous reaction.
4. is positive for a non-spontaneous reaction.
A necessary condition for an adiabatic change is:
1. ∆T = 0
2. ∆P = 0
3. q = 0
4. w = 0
The enthalpy of formation of all elements in their standard state is-
1. | Unity | 2. | Zero |
3. | Less than zero | 4. | Different for each element |
for combustion of methane is –x kJ mol–1.
The value of for the same reaction would be:
701 J of heat is absorbed by a system and 394 J of work is done by the system. The change in internal energy for the process is:
1. | 307 J | 2. | -307 J |
3. | 1095 J | 4. | -701 J |
The reaction of cyanamide, with dioxygen, was carried out in a bomb calorimeter, and ∆U was found to be at 298 K.
\(\small{\mathrm{NH}_2 \mathrm{CN}(\mathrm{s})+\frac{3}{2} \mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{N}_2(\mathrm{g})+\mathrm{CO}_2(\mathrm{g})+\mathrm{H}_2 \mathrm{O}(\mathrm{l})}\)
The enthalpy change for the reaction at 298 K would be: