Introduction to Biochemistry - Quiz 1.1.4

The available options are spontaneous and non-spontaneous. 

A reaction that has a negative free energy delta is spontaneous. Therefore the answer is spontaneous.

Again, the available options are spontaneous and non-spontaneous. 

We know $ \Delta G = \Delta H - T \Delta S = -10 - 15T < 0 $, therefore the answer is spontaneous.

This is basically the generalization of above, the free energy is always less than 0 in this case, and therefore the answer is still spontaneous.

$ K_{eq} = \frac{[P]}{[S]} $, that means at equilibrium, the concentration of [P] should be 4 times the concentration of [S], but right now we have 10M of [P], according to the Le Chatelier principle, the reaction will go backward, therefore the answer is that the forward reaction is non-spontaneous.

According to the Le Chatelier principle, the reduction of product should leads to production of product, therefore the reaction will go forward.

Remember the standard condition is not just the standard temperature, it is also the reactant has a concentration of 1M.

According to the equation $ \Delta G = RT\ln K_{eq} $, since $ K_{eq} = 1 $, $ \Delta G = 0 $. The reaction is at equilibrium because the concentration is all at 1M now (by the definition of standard condition).