Question

Use standard free energies of formation to calculate ΔG∘ at 25∘C for each of the following reactions. Answers must be in Kj.

Part A N2O4(g)→2NO2(g) Express your answer using two significant figures.

Part B NH4Cl(s)→HCl(g)+NH3(g) Express your answer using three significant figures.

Part C 3H2(g)+Fe2O3(s)→2Fe(s)+3H2O(g) Express your answer using three significant figures.

Part D N2(g)+3H2(g)→2NH3(g) Express your answer using three significant figures.

Part E How do the values of ΔG∘ calculated this way compare to those calculated from ΔH∘ and ΔS∘? Which of the two methods could be used to determine how ΔG∘ changes with temperature? Essay answers are limited to about 500 words (3800 characters maximum, including spaces). 3800 characters maximum.

Answer 1

Part A

The reaction is

The free energy of the reaction=

Energy of formation for

Part B

Reaction is:

Part C

Part D

Part E

First calculate the enthalpy of reaction from the formula

For reaction 1

The reaction is

Enthalpy of reaction is

For calculation of entropy

For reaction 1

Entropy of reaction is

The formula for calculation of using is

For the given reaction the standard free energy of reaction calculated from energies of formation is higher than the standard free energy of reaction calculated from enthalpy and entropy of the reaction.

So we can say the Free energy of reaction is dependent of temperature.

Standard Gibbs free energies of formation are constant for molecules.

However changes with temperature and should be calculated only using the equation