Gibbs Energy Change and Equilibrium

IMPORTANT

Gibbs Energy Change and Equilibrium: Overview

This topic covers concepts such as Gibbs Free Energy and Spontaneity, Gibbs Free Energy, Gibbs Energy Change as Driving Force, Criteria for Spontaneity in Terms of Gibbs Energy Change, and Physical Significance of Gibbs Free Energy Change.

Important Questions on Gibbs Energy Change and Equilibrium

MEDIUM
IMPORTANT

The correct relationship between free energy and equilibrium constant K of a reaction is:                              

MEDIUM
IMPORTANT

Consider the following reaction occurring in automobile

2C8H18+25O2g16CO2g+18H2Og

the sign of  ΔH,  ΔS  and  ΔG would be:

EASY
IMPORTANT

Match list-I (Equations) with List-II (Type of processes) and select the correct option.
 

  List I   List II
  Equations   Type of processes
(1) Kp > Q (i) Non spontaneous
(2) Δ G o < RTInQ (ii) Equilibrium
(3) Kp = Q (iii) Spontaneous and endothermic
(4) T > Δ H Δ S (iv) Spontaneous

EASY
IMPORTANT

A chemical reaction will be spontaneous if it is accompanied by a decrease of

                               

EASY
IMPORTANT

The enthalpy and entropy change for the reaction

  B r 2 (l)+C l 2 (g)2BrCl(g)

are   30kJmo l 1 and105J K 1 mo l 1  respectively. The temperature at which the reaction will be in equilibrium is

                               

MEDIUM
IMPORTANT

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?

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IMPORTANT

Standard enthalpy and standard entropy changes for the oxidation of ammonia at 298 K are -382.64kJmol1  and  145.6JK1mol1,  respectively. The standard Gibbs energy change for the same reaction at 298 K is:

                               

EASY
IMPORTANT

The entropy change in the fusion of one mole of a solid melting at  27°C (Latent heat of fusion,  2930Jmol1) is:

                               

MEDIUM
IMPORTANT

For the reaction N2g+3H2g2NH3g;H=-99.4kJ and S=-198.3JK-1. The temperature at which the system is in equilibrium is

MEDIUM
IMPORTANT

For the reaction at 298 K  2 A+B=C
ΔH=40kJmol-1 and ΔS=0.02 kJmol-1K-1. At what temperature will the reaction becomes spontaneous considering ΔH and ΔS to be constant over the temperature range,

MEDIUM
IMPORTANT

If G for a reaction is negative, the change is:

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IMPORTANT

The maximum work (in kJ mol-1) that can be derived from complete combustion of 1 mole of CO at 298 K and 1 atm is [Standard enthalpy of combustion of CO=-283.0 kJ mol-1; standard molar entropies at 298 K: SO2=205.1 J mol-1, SCO=197.7 J mol-1. SCO2=213.7 J mol-1]

MEDIUM
IMPORTANT

Which condition among the following holds true at the stage of half-completion for the reaction AB ?

EASY
IMPORTANT

The boiling point of water at 1 atm is 100°C. Which among the following is true for vaporization of water at 75°C ?

MEDIUM
IMPORTANT

For the process

H2Ol1 bar, 373 KH2O(g)(1 bar, 373 K) , the correct set of thermodynamic parameters is

EASY
IMPORTANT

A reaction at 1 bar is non-spontaneous at low temperature but becomes spontaneous at high temperature. Identify the correct statement about the reaction among the following:

MEDIUM
IMPORTANT

For the reaction 2O33O2, ΔH, ΔS and G are respectively:

EASY
IMPORTANT

Assuming ideal behaviour, the magnitude of log K for the following reaction at 25°C is x×10-1. The value of x is____________. (Integer answer) 3HCCH(g)C6H6(l) [Given : ΔfG°(HCCH)=-2.04×105] mol-1; ΔfG°C6H6=-1.24×105 J mol-1
R=8.314 J K-1 mol-1]

MEDIUM
IMPORTANT

For a dimerization reaction, 2A(g)A2(g) at 298 K,

 ΔU=-20 kJ mol-1, ΔS=-30 J mol-1, then the magnitude of ΔG will be________kJ.

Round off your answer to the nearest integer after multiplying with 2.

EASY
IMPORTANT

Products are favoured in a chemical reaction taking place at a constant temperature and pressure. Consider the following statements:
(i) The change in Gibbs energy for the reaction is negative.
(ii) The total change in Gibbs energy for the reaction and the surroundings is negative.
(iii) The change in entropy for the reaction is positive.
(iv) The total change in entropy for the reaction and the surroundings is positive.

The statements which are ALWAYS true are:-