What is the value of the equilibrium constant at 655 K for each of the following reactions?

2NO_2(g)harrN_2O_4(g)
Br_2(g)+Cl_2(g)harr2BrCl(g)

I figured out how to calculate DeltaG^0 using DeltaH^0 and DeltaS^0, but I am unable to determine the value for DeltaG because it is not at STP. Do I just plug in DeltaG^0 to the -RTlnK equation to find the value of K, or do I have to adjust something for its not being at STP?

1 Answer
Al E.
Nov 17, 2017

K approx 1.67

Explanation:

Yes! You're correct, I'll do the first one.

2NO_2(g) rightleftharpoons N_2O_4(g)

DeltaG^0 approx -2.8kJ

I did that per the usual method using a table in my text.

-2.8*10^3 J = -(8.314J)/(mol*K)* (655K) * lnK
therefore K approx 1.67

This is reasonable because, I did a quick check and noticed this reaction has favorable enthalpy but unfavorable entropy. Thus, it will be nonspontaneous at high temperatures. Thus, not much product will form relative to standard conditions.

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