Constant is K and that is the the concentration of product over the concentration of reactant for example for the equlibrium equation below
A+2B=3C
K= [C]^3/( [A]* [B]^2
I believe the correct answer would be D.
i may be wrong but i think its B. neutralization
That new volume will be 0.25 L. You use the formula P1V1 = P2V2.