AP Chemistry Question of the Day --21

Welcome back to my blog. Here comes the answer to question 20 I posted yesterday. The correct answer is A. 

 Since both K and KCl are solids, the equilibrium constant is expressed as:

 If the reaction goes essentially to completion, that means the concentration of chlorine gas is minimal, which in turn shows that K has a very big value.

according to

Delta G will have a big negative number, which means that the reaction is thermodynamically favoured  (which used to be called spontaneous in earlier AP reviews). 

Looking at the reaction equation, we see on the reactant side, there is one gas molecule and on the product side, there is no gas molecules. This indicates that the entropy is decreasing for the reaction. 

So, only answer A is the correct answer.

Following is Question 21 of the series. It is in continuation of Question 17, 18, 19 and 20. 

21 . The elements K and Cl react directly to form the compound KCl according to the equation below.

Which of the following expressions is equivalent to ΔH for the reaction represented above?

(A) x + y

(B) x – y

(C) x + 2y

(D) x/2– y

I will post the answer and explanation tomorrow. 

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