The enthalpies of formation of Al₂O₃ and Cr₂O₃ are -1596 kJ and -1134 kJ respectively. $∆$H for the reaction,

2Al + Cr₂O₃  → 2Cr+ Al₂O₃ is

• -2730 kJ

• -462 kJ

• -1365 kJ

• +2730 kJ

A process is taking place at constant temperature and pressure. Then

• ΔH = ΔE=0

• ΔH= TΔS

• ΔH= 0

• ΔS= 0

The enthalpy of combustion of methane at 25°C is 890 kJ. The heat liberated when 3.2 g of methane burnt in air is

• 445 kJ

• 278 kJ

• -890 kJ

• 178 kJ

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 $∆$H is the enthalpy change and $∆$E is the change in internal energy, then

• $∆\mathrm{H} > ∆\mathrm{E}$

• $∆\mathrm{H} < ∆\mathrm{E}$

• $∆\mathrm{H} = ∆\mathrm{E}$

• the relationship depends on the capacity of the vessel

For a system in equilibrium, $∆$G= 0, under conditions of constant ...............

• temperature and pressure

• temperature and volume

• pressure and volume

• energy and volume

186.

Molar heat of vaporisation of a liquid is 6 kJ mol^-1. If the entropy change is 16 J mol^-1 K^-1, the boiling point of the liquid is:

• 375°C

• 375 K

• 273 K

• 102°C

0.06 mole of KNO₃ solid is added to 100 cm³ of water at 298K. The enthalpy of KNO₃ aqueous solution is 35.8 kJ mol^-1. After the solute is dissolved the temperature of the solution will be:

• 293 K

• 298 K

• 301 K

• 304 K

ΔG° vs T plot in the Ellingham's diagram slopes upwards for the reactions:

• Mg+ 1/2O₂ → MgO

• 2Ag + 1/2O₂ → Ag₂O

• C + 1/2O₂ → CO

• CO + 1/2O₂ → CO₂

For a reaction to be spontaneous at all temperatures :

• ΔG and ΔH should be negative

• ΔG and ΔH should be positive

• ΔG =ΔS = 0

• ΔH< ΔG

For a reversible reaction:

$\mathrm{X}\left(\mathrm{g}\right) + 3\mathrm{Y} \left(\mathrm{g}\right) \rightleftharpoons 2\mathrm{Z} \left(\mathrm{g}\right) ; ∆\mathrm{H} = -40\mathrm{kJ}$, the standard entropies of X, Y and Z are 60, 40 and 50 JK^-1 mol^-1 respectively. The temperature at which the above reaction attains equilibrium is about :

• 400 K

• 500 K

• 273 K

• 373 K