Competitive Thinking

For the reaction, ${\mathrm{X}}_{\mathrm{2}}{\mathrm{O}}_4 \left(\mathrm{l}\right)\mathrm{ }\stackrel{}{\to } 2{\mathrm{XO}}_2 \left(\mathrm{g}\right); ∆\mathrm{U}=2.1 \mathrm{kcal}, ∆\mathrm{S}= 20 \mathrm{kcal} {\mathrm{K}}^{\mathrm{-1}}$ at $300 \mathrm{K}$. Hence, $∆\mathrm{G}$ is ______.

The entropy of a perfectly crystalline solid at absolute zero is:

Which law of thermodynamics helps in calculating entropy at different temperatures?
 

A heat engine absorbs heat ${\text{Q}}_{\text{1}}$ at temperature ${\text{T}}_{\text{2}}$ and heat ${\text{Q}}_{\text{2}}$ at temperature ${\text{T}}_{\text{2}}$. Work done by the engine is ${\text{(Q}}_{\text{1}}{\text{+Q}}_{\text{2}}\text{)}$. This data:

What is the free energy change in dissolving one mole of $\mathrm{NaCl}$ with its lattice energy and hydration energy of $\mathrm{777.8 }\mathrm{kJ} {\mathrm{mol}}^{\mathrm{-1}} \mathrm{and} -774 \mathrm{kJ} {\mathrm{mol}}^{\mathrm{-1}}$, respectively at ${25}^{\mathrm{o}}\mathrm{C}?$ (Given : $∆\mathrm{S}=0.043 \mathrm{kJ} {\mathrm{K}}^{\mathrm{-1}} {\mathrm{mol}}^{\mathrm{-1}}$)

For the reaction ${\mathrm{X}}_{\mathrm{2}}{\mathrm{Y}}_4 \left(\mathrm{l}\right)\mathrm{ }\stackrel{}{\to } 2{\mathrm{XY}}_2 \left(\mathrm{g}\right)$ at $300 \mathrm{K}$ the values of $∆\mathrm{U}$ and $∆\mathrm{S}$ are $\mathrm{2 }\mathrm{kCal}$ and $\mathrm{20 }\mathrm{Cal} {\mathrm{K}}^{\mathrm{-1}}$, respectively. The value of $∆\mathrm{G}$ for the reaction is ______.

The heats of vaporisation of ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}, {\mathrm{C}}_{\mathrm{2}}{\mathrm{H}}_{\mathrm{5}}\mathrm{OH} \text{and} {\mathrm{CS}}_{\mathrm{2}} \text{are} 40.6 \mathrm{kJ} {\mathrm{mol}}^{\mathrm{-1}}, 38.6 \mathrm{kJ} {\mathrm{mol}}^{\mathrm{-1}} \text{and} 26.8 \mathrm{kJ} {\mathrm{mol}}^{\mathrm{-1}}$, respectively. The strength of intermolecular forces in these liquids is in the order of _______.

The entropy change involved in the isothermal reversible expansion of $2 \mathrm{moles}$ of an ideal gas from a volume of $10 \mathrm{L}$ to $100 \mathrm{L}$ at $27°\mathrm{C}$ is _____.