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. $∆\mathrm{G}$ is zero for a reversible reaction.

2. $∆\mathrm{G}$ is positive for a spontaneous reaction.

3. $∆\mathrm{G}$ is negative for a spontaneous reaction.

4. $∆\mathrm{G}$ is positive for a non-spontaneous reaction.

The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound is :

Find the correct relationship between the magnitudes of heat evolved (x and y) in the following reactions.

Reaction (i):

C(g) + 4H(g) → CH₄(g)

Magnitude of heat evolved = x kJ mol⁻¹

Reaction (ii):

C(graphite) + 2H₂(g) → CH₄(g)

Magnitude of heat evolved = y kJ mol⁻¹

Which of the following algebraic relationships is correct based on the given thermochemical equations?

1. z = x + y

2. x = y + z

3. x = y - z

4. y = 2z - x

The entropy change can be calculated by using the expression $∆\mathrm{S}=\frac{{\mathrm{q}}_{\mathrm{rev}}}{\mathrm{T}}$. When water freezes in a glass beaker, the correct statement among the following is:

The pressure-volume work for an ideal gas can be calculated by using the expression $\mathrm{W}={\int }_{{\mathrm{V}}_{\mathrm{i}}}^{{\mathrm{V}}_{\mathrm{f}}}{\mathrm{p}}_{\mathrm{ext}}d\mathrm{V}$.

The work can also be calculated from the pV-plot by using the area under the curve within the specified limits.
An ideal gas is compressed (a) reversibly or (b) irreversibly from volume ${\mathrm{V}}_{\mathrm{i}}$ to ${\mathrm{V}}_{\mathrm{f}}$.
The correct option is:

Calculate the correct values of heat transfer (q), change in temperature (ΔT), and work done (W) for the free expansion of an ideal gas under adiabatic conditions.
1.  q = 0, ΔT ≠ 0, W = 0
2.  q ≠ 0, ΔT = 0, W = 0
3.  q = 0, ΔT = 0, W = 0
4.  q = 0, ΔT = 0, W ≠ 0

During the complete combustion of one mole of butane, 2658 kJ of heat is released. The thermochemical reaction for this change is: