For a reaction
Diagram showing a reaction where P decomposes into Q and R.
Reaction 1: Pk1Q
Reaction 2: Pk2R
Initial concentration of P at t=0 is a .
Concentration of P at time t is (a−x) .
dtd[x] is equal to
(A) k1(a−x)−k2(a−x)
(C) k1(a−x)+k2(a−x)
(B) k2(a−x)−k1(a−x)
(D) −k1(a−x)−k2(a−x)