Question

For any system that may undergo any process, we expect the process to occur spontaneously only if ∆G_universe <0. For a chemical system that may react, ∆G_sys = RT ln(Q/K), so under standard state conditions (where [X] º 1 M and P_X º 1 atm) ∆G_sys = ∆G° = RT ln(1/K) = –RT lnK. Thus, at equilibrium (where Q = K), ∆G = RT ln(1) = 0. Use these ideas to explain why the laws of thermodynamics predict that no chemical reaction in a closed system should ever go to 100% completion.

Answer 1

As mentioned in the question

Also for a system to move in forward direction,

before eqm is reached Q< K, an hence condition is satisfied.

at eqm so system has the tendency to neuther move in forward or reverse direction.

Now let us assume the case when system tries to move forward beyound eqm point. Now eqm point at maximum can be reaced when 100% completion happens. So in this llimiting case Q>K which means and hence system will move in backward direction. Hence no chemical reaction in a closed system should ever go to 100% completion.