The bond dissociation energies of $A_2, B_2$ and $A B$ are in the ratio $1: 4: 2$. If $\Delta H$ for formation of $A B$ from $A_2$ and $B_2$ is $-100 \mathrm{~kJ} / \mathrm{mol}$, calculate the bond dissociation energy of $B_2$.

The temperature of $K$ at which $\Delta G=0$, for a given reaction with $\Delta H=-20.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $\Delta S=-50.0 \mathrm{~JK}^{-1} \mathrm{~mol}^{-1}$ is

A mixture of two moles of carbon monoxide and one mole of oxygen, in a closed vessel is ignited to convert the carbon monoxide to carbon dioxide. If $\Delta H$ is the enthalpy change and $\Delta E$ is the change in internal energy, then

The value of enthalpy change $(\Delta H)$ for the reaction $\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}(l)+3 \mathrm{O}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{CO}_2(\mathrm{~g})+ 3 \mathrm{H}_2 \mathrm{O}(l)$, at $27^{\circ} \mathrm{C}$ is $-1366 \cdot 5 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The value of internal energy change for the above reaction at this temperature will be

Standard entropy of X₂, Y₂ and XY₃ are 60, 40 and 50 JK^$-$1mol^$-$1, respectively. For the reaction, $\frac{1}{2}$X₂ + $\frac{3}{2}$Y₂ $\to$ XY₃, $\Delta$H = $-$30 kJ, to be at equilibrium, the temperature will be

In an adiabatic process, no transfer of heat takes place between system and surrounding. Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following.

SI unit of Boltzmann's constant is

For the complete combustion of ethanol, ${C_2}{H_5}OH(I) + 3{O_2}(g) \to 2C{O_2}(g) + 3{H_2}O(I)$, the amount of heat produced as measured in bomb calorimeter is 1364.47 kJ mol^$-$1 at 25$^\circ$C. Assuming ideality the enthalpy of combustion, $\Delta$H_C, for the reaction will be (R = 8.314 JK^$-$1 mol^$-$1)

The incorrect expression among the following is

Which of the following statement is correct?

At the top of a mountain the thermometer reads 0$^\circ$C and the barometer reads 710 mm Hg. At the bottom of the mountain the temperature is 30$^\circ$C and the pressure is 760 mm Hg. The ratio of the density of air at the top to that of the bottom is

The enthalpies of combustion of carbon and carbon monoxide in excess of oxygen at 298 K and constant pressure are $-$393.5 kJ/mol and $-$280.0 kj/mol respectively. The heat of formation of carbon monoxide at constant volume is