Question

2B(s) + 3F2(g) 2BF3(g).

Which equilibrium expression is correct?

Answer 1

2 B(s) + 3 F₂(g) = 2 BF₃(g)

Kc = products / reagents

Kc = [ BF₃ ]² / [ B ]² . [ F₂ ]³

hope this helps!