Gibbs Free Energy (G)

Author:Tamil Nadu Board
11th Tamil Nadu Board
IMPORTANT

Gibbs Free Energy (G): Overview

This topic defines Gibbs free energy and explains the net work done by the system. It discusses the effects of temperature on the spontaneity of reactions. Relationship between standard free energy change and equilibrium constant is given here.

Important Questions on Gibbs Free Energy (G)

MEDIUM
IMPORTANT

For a chemical reaction the values of H and ΔS at 300 K are -10 kJ mole-1 and -20 J K-1mol-1 respectively. What is the value of G of the reaction? Calculate the ΔG of a reaction at 600 K assuming ΔH and ΔS values are constant. Predict the nature of the reaction.

HARD
IMPORTANT

Find out the value of the equilibrium constant for the following reaction at 298 K,  2NH3(g)+CO2(g)  NH2CONH2(aq)+H2O(l). Standard Gibbs energy change, Gr° at the given temperature is -13.6 kJmol-1.

 

HARD
IMPORTANT

For the reaction at 273 K : 2A+B  C

H=400 Jmol-1 ; S=0.2 JK-1mol-1. Determine the temperature at which the reaction would be spontaneous.

HARD
IMPORTANT

At 33 KN2O4 is fifty percent dissociated. Calculate the standard free energy change at this temperature and at one atmosphere.

HARD
IMPORTANT

When 1-pentyne (A) is treated with 4 N alcoholic KOH at 175°C, it is converted slowly into an equilibrium mixture of 1.3%  1-pentyne (A),95.2%  2-pentyne (B) 3.5% 1,2-pentadiene (C) of  and the equilibrium was maintained at 175°C, calculate G° for the following equilibria.

B  A     G1°=?B  C      G2°=?

 

HARD
IMPORTANT

What is the equilibrium constant Keq for the following reaction at 400 K?

2NOCl(g)  2NO(g)+Cl2(g), given that H°=77.2 kJmol-1 ; and S°=122 JK-1mol-1.

HARD
IMPORTANT

For the reaction Ag2O(s)   2Ag(s)+12O2(g) : H=30.56 kJmol-1 and S=6.66 JK-1mol-1. Calculate the temperature at which G is equal to zero. Also predict the direction of the reaction below this temperature.

HARD
IMPORTANT

For the reaction Ag2O(s)  2Ag(s)+12O2(g) : H=30.56 kJmol-1 and S=6.66 JK-1mol-1. Calculate the temperature at which G is equal to zero. Also predict the direction of the reaction at this temperature.

HARD
IMPORTANT

30.4 kJ is required to melt one mole of sodium chloride. The entropy change during melting is 28.4 J K-1mol-1. Calculate the melting point of sodium chloride.

HARD
IMPORTANT

List the characteristics of Gibbs free energy.

HARD
IMPORTANT

What are spontaneous reactions? What are the conditions for the spontaneity of a process?

HARD
IMPORTANT

The equilibrium constant of a reaction is 10, what will be the sign of ΔG? Will this reaction be spontaneous?

HARD
IMPORTANT

Define Gibbs free energy.

HARD
IMPORTANT

Predict the feasibility of the reaction when H decreases but S increases.

HARD
IMPORTANT

Predict the feasibility of the reaction when both H and S are negative.

HARD
IMPORTANT

Predict the feasibility of the reaction when both H and S are positive.

MEDIUM
IMPORTANT

The values of H and S for a reaction are respectively 30 kJ mol-1 and 100 J K-1 mol-1. Then the temperature above which the reaction will become spontaneous is

EASY
IMPORTANT

The correct thermodynamic conditions for the spontaneous reaction at all temperature is

HARD
IMPORTANT

All the naturally occurring processes proceed spontaneously in a direction which leads to