Answer to Question #156541 in General Chemistry for ash

Question

1. Determine whether each of the following statements is true or false:
2. An exothermic reaction is always spontaneous
3. When ΔG° is positive, the reaction cannot occur under any conditions.
4. ΔS° is positive for a reaction in which there is an increase in the number of moles.
5. If ΔH° and ΔS° are both negative, ΔG°, will be negative.

Answer 1

1. An exothermic reaction is always spontaneous FALSE: reaction is spontaneous only if ΔG° is negative, not ΔH°
2. When ΔG° is positive, the reaction cannot occur under any conditions. FALSE: positive ΔG° just means that the reaction isn't spontaneous. Such a reaction may occur if there is an input of free energy.
3. ΔS° is positive for a reaction in which there is an increase in the number of moles. FALSE: you also need to know the matters of state of products and reactants. Gases have the largest S ans solids have the smallest S for the same substance.
4. If ΔH° and ΔS° are both negative, ΔG°, will be negative. FALSE: ΔG° = ΔH° - T*ΔS° so ΔG° could be both negative or positive depending on the values of H and S