posted by Andrea .
0.80 mol/L of A and B are mixed. They react very slowly to produce C and D as follows:
A(aq) + B(aq) ⇔ C(aq) + 2D(aq)
When equilibrium is attained, the concentration of C is 0.60 mol/L and the concentration of A is:
a) 0.20 M
b) 0.40 M
c) 0.60 M
d) 0.80 M
Isn't this just subtraction of one reagent from another?