Chemistry Question Bank

A reaction occurs spontaneously if (2005)

If the bond energies of H–H, Br–Br, and H–Br are 433, 192 and 364 kJ mol–1 respectively, the H for the reaction 2(g) 2(g) (g) H Br 2HBr → is (2004)

The densities of graphite and diamond at 298 K are 2.25 and 3.31 g cm–3, respectively. If the standard free energy difference is equal to 1895 J mol–1, the pressure at which graphite will be transformed into diamond a…

The following data is known about the melting of a compound AB. ∆H = 9.2 kJ mol–1. ∆S = 0.008 kJ K–1mol–1. Its melting point is :

Identify the correct statement for change of Gibbs’ energy for a system system ( G ) at constant temperature and pressure. (2006)

The enthalpy and entropy change for the reaction: 2(l) 2(g) (g) Br Cl 2BrCl → are 30 kJ mol–1 and 105JK–1 mol–1 respectively. The temperature at which the reaction will be in equilibrium is (2006)

For the reaction, 2H O g 2H g O g → ∆H = 571.6 KJ fH of water is :

For the gas phase reaction, 5(g) 3(g) 2(g) PCl PCl Cl Which of the following conditions are correct? (2008)

H and E  for the reaction, Fe O s 3H g 2Fe s H O l → at constant temperature are related as (a) H E (b) H E RT (c) H E RT (d) H E 3RT

From the following bond energies: H — H bond energy : 431.37 kJ mol–1 C == C bond energy : 606.10 kJ mol–1 C — C bond energy : 336.49 kJ mol–1 C — H bond energy : 410.50 kJ mol–1 Enthalpy for the reaction, will be (2009)

Which of the following reactions define o f G ? (a) diamond C O g CO g → (b) H g F g HF g → (c) H P O H O 2H PO → (d) SO g O g SO g →

The enthalpy of vaporisation of a compound AB at its boiling point (127°C) is 6.4 kJ mol-1. Its entropy of vaporization is

∆H for the reaction, SO g O g SO g ∆H = –98.3 kJ If the enthalpy of formation of SO₃(g) is –395.4 kJ then the enthalpy of formation of SO₂(g) is :

In which of the following cases, the reaction is spontaneous at all temperatures ?

2 moles of ideal gas at 27°C temperature is expanded reversibly from 2 lit. to 20 lit. find entropy change. (R = 2 cal/mol K)

Cell reaction is spontaneous when (a) G is negative (b) G is positive (c) red G is positive (d) red G is negative

Enthalpy change for the reaction, 4H(g)  → 2H₂(g) is – 869.5 kJ. The dissociation energy of H–H bond is

G is the net energy available to do useful work and is a measure of free energy. If a reaction has positive enthalpy change and positive entropy change, under what conditions will the reaction be spontaneous?

When 0.5 g of sulphur is burnt to SO₂ 4.6 kJ of heat is liberated. What is the enthalpy of formation of sulphurdioxide?

Assume each reaction is carried out in an open container. For which reaction will H = E ? (CBSE AIPMT 2006) (a) H (g) Br (g) 2HBr(g) → (b) C(s) 2H O(g) 2H (g) CO (g) → (c) PCl (g) PCl (g) Cl (g) → (d) 2CO(g) O (g) 2CO…

Standard entropies of X2, Y₂ and XY₃ are 60, 40 and 50 J K–1 mol–1 respectively. For the reaction 1/2X2 + 3/2Y₂ ⇌ XY₃, ∆H = –30 kJ, to be at equilibrium, the temperature should be (2010)

One mole of an ideal diatomic gas (Cv = 5 cal) was transformed from initial 25°C and 1 L to the state when temperature is 100°C and volume 10 L. The entropy change of the process can be expressed as (R = 2 calories/mo…

When one mole of an ideal gas is compressed to half of its initial volume and simultaneously heated to twice its initial temperature, the change in entropy of gas (∆S) is :

A reaction has ∆H = – 33 kJ and ∆S = +58 J/K. This reaction would be :

In which case change in entropy is negative?