In any chemical reaction, a quantity that decrease to a minimum is

• free energy

• entropy

• temperature

• enthalpy

Given, H₂O (l) → H₂O (g); $∆$H₁ = +43 kJ

H₂O (s) → H₂O (l); $∆$H₂ = +6.05 kJ. Calculate the enthalpy of sublimation of ice.

• 49.75 kJ mol^-1

• 37.65 kJ mol^-1

• 43.7 kJ mol^-1

• 55.23 kJ mol^-1

Heat formation of H₂O is -188 kJ/ mol and H₂O₂ is 286 kJ/mol. The enthalpy change for the reaction; 2H₂O₂ → 2H₂O + O₂ is

• 196 kJ

• -196 kJ

• 984 kJ

• -984 kJ

When 1 mole of a gas is heated at constant volume, temperature is raised from 298 K to 308 K. Heat supplied to the gas is 500J. Then, which statement is correct?

• q= -W = 500J : ΔE= 0

• q= W = 500J : ΔE= 0

• q = ΔE= 500J , W= 0

• ΔE = 0; q= W = -500J

If enthaplies of formation for C₂H₂(g), CO₂(g) and H₂O(l) at 25°C and 1atm pressure be 52, -394 and -286kJ mol^-1 respectively, then the enthaply of combustion of C₂H₄(g) will be

• -141.2 kJ mol^-1

• -1412 kJ mol^-1

• + 141.2 kJ mol^-1

• + 1412 kJ mol^-1

The enthalpy of combustion for the H₂, cyclohexene and cyclohexane are -241, -3800 and -3920 kJ mol^-1 respectively. Heat of hydrogenation of cyclohexene is

• 121 kJ mol^-1

• -121 kJ mol^-1

• 242 kJ mol^-1

• -242 kJ mol^-1

Which one of the following is not a state function?

• Internal energy

• Work

• Entropy

• Free energy

228.

Given that N₂(g) + 3H₂(g) → 2NH₃(g): Δ_rH° =-92kJ, the standard molar enthalpy of formation in kJ mol^-1 of NH₃(g) is 

• -92

• +46

• +92

• -46

In view of ${∆}_{\mathrm{r}}\mathrm{G}°$ for the following reactions

PbO₂ + Pb → 2PbO, ${∆}_{\mathrm{r}}\mathrm{G}°\mathrm{r}$

SnO₂ + Sn → 2SnO, ${∆}_{\mathrm{r}}\mathrm{G}°\mathrm{r}$

Which oxidation state is more characteristic for lead and tin?

• For lead +2, for tin +2

• For lead +4, for tin +4

• For lead +2, for tin +4

• For lead +4, for tin +2

The enthalpy of the formation of CO₂ and H₂O are -395 kJ and -285 kJ respectively and the enthalpy of combustion of acetic acid is 869 kJ. The enthalpy of formation of acetic acid is

• 340 kJ

• 420 kJ

• 491 kJ

• 235 kJ