Question

A) For the reaction of oxygen and nitrogen to form nitric oxide, consider the following thermodynamic data (Due to variations in thermodynamic values for different sources, be sure to use the given values in calculating your answer.):

ΔHrxn∘	180.5kJ/mol
ΔSrxn∘	24.80J/(mol⋅K)

Calculate the temperature in kelvins above which this reaction is spontaneous.

Express your answer to four significant figures and include the appropriate units.

B) The thermodynamic values from part A will be useful as you work through part B:

ΔH∘rxn	180.5kJ/mol
ΔSrxn∘	24.80J/(mol⋅K)

Calculate the equilibrium constant for the following reaction at room temperature, 25∘C:

N2(g)+O2(g)→2NO(g)

Express your answer numerically to three significant figures.

Can you help me solve Part A and Part B? Thank you!

Answer 1

A)

For a spontaneous reaction:
And

Here,

ΔHrxn∘	180.5kJ/mol
ΔSrxn∘	24.80J/(mol⋅K) = 0.0248 kJ/(mol.K)

Rearrange:

So, temperature in kelvins above which this reaction is spontaneous = 7278 K

B)

Equilibrium constant is related to by following relation:

Here, R is the universal gas constant, T is the temperature in kelvins and K is the equilibrium constant.

For this reaction:

ΔH∘rxn	180.5kJ/mol
ΔSrxn∘	24.80J/(mol⋅K) = 0.0248kJ /(mol.K)
T	25'C = 25 +273 = 298K

Therefore,

As we know,
So,   

  

R = 8.314 J/mol-K T = 298K

So, RT = 8.314 J/mol-K x 298 K = 2477.57 J/mol = 2.48 kJ/mol

So, equilibrium constant = 4.86 x 10^-31