Question

Describe the nature of the interactions in a solution with positive DSexcess , DS excess negative , DG positive excess DG , DG negative excess, excess DH greater than zero and excess DH less than zero excess.

Answer 1

1) For an increase in entropy DS has a positive value; for a decrease in entropy DS has a negative value.

if a chemical reactions occur spontaneously if DS is calculated to be a positive value and there is a decrease in entropy

For a spontaneous change the total entropy must increase, DS_total > 0.

For a nonspontaneous change the total entropy must decrease, DS_total<0

2) DG is dependent on temperature, so a chemical reaction that is not spontaneous at one temperature might be spontaneous at anotther.

ΔG < 0 reaction can spontaneously proceed to the right:   A → B

ΔG >0 reaction can be non spontaneous proceed to the left : A<---- B

ΔG = 0 the reaction is at equilibrium; the quantities of A and B will not change

3)A reaction is Exothermic Reaction if DH < 0 (negative) and reaction gives off heat.

A reaction is Endothermic Reaction if DH > O (positive) and reaction absorbs heat.

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