Consider the following reaction: 2NO(g)+O2(g)→2NO2(g)
Estimate ΔG∘ for this reaction at each of the following temperatures and predict whether or not the reaction will be spontaneous. (Assume that ΔH∘ and ΔS∘ do not change too much within the give temperature range.) I need to find the temperature are 298K and 702K. For 298K It is simple because at standard temperature
ΔG∘ = DG(products)- DG(reactants).

A. ; as such the reaction is said to be spontaneous since the value of is negative.

B.   and the reaction is spontaneous

Explanation:

The equation for this chemical reaction is :

Using the following relation to calculate ;

At 298 K; the standard Gibbs Free Energy for the formation are as follows:

Replacing them into the above equation;

Thus; ; as such the reaction is said to be spontaneous since the value of is negative.

B.

Using the same above chemical equation;

The relation used for calculating of the reaction when the temperature is 702 K is:

where;

Gibbs free energy of the reaction at 702 K

= standard enthalpy of the reaction = -116.2 kJ/mol

= standard entropy of the reaction = -146.6 J/mol/K

Temperature T = 702 K

Thus and the reaction is spontaneous

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante