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481.
Enthalpy of formation of HF and HCl are -161 kJ and -92 kJ respectively. Which of the following statements is incorrect?

HCl is more stable than HF

HF and HCl are exothermic compounds

The affinity of fluorine to hydrogen is greaterthan the affinity of chlorine to hydrogen

HF is more stable than HCl

HCl is more stable than HF

HF is more stable than HCl. The reason is that in the formation of HF, more energy is produced. It means, HF has less energy than HCl and hence is more stable.

In other words, we need more energy to break H-Fbond, hence HF is more stable.

482.

The enthalpy of reaction,

$H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (g) is ∆ H_{1} and that of H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l) is ∆ H_{2} . Then$

ΔH₁ < ΔH₂
ΔH₁ + ΔH₂ = 0
ΔH₁ > ΔH₂
ΔH₁ = ΔH₂

483.

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

484.

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

ΔH = ΔE=0
ΔH= TΔS
ΔH= 0
ΔS= 0

485.

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

486.

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

$∆ H > ∆ E$
$∆ H < ∆ E$
$∆ H = ∆ E$
the relationship depends on the capacity of the vessel

487.

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

temperature and pressure
temperature and volume
pressure and volume
energy and volume

488.

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

489.

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: