A(g) + 2B(g) = 3C(g)
(2)求用A來表示的反應(yīng)的平均速率：
v(A) = - △C(A) / △t = -(0.8-1.0) / 2 = 0.1 (mol/L·min)
(1)2min末B,C的濃度
求B的濃度,設(shè)為x：
v(B) = 2v(A) = - △C(B) / △t = - (x - 1.2) / 2 = 0.1*2
x = 0.8 (mol/L)
求C的濃度,設(shè)為y：
v(C) = 3v(A) = △C(C) / △t = (y-0) / 2 = 0.1*3
y = 0.6 (mol/L)