*Consider the following hypothetical reaction mechanism A + 3B → 2C. The rate of appearance of C given by d[C]/dt may also be expressed as:
A) d[C]/dt = d[A]/dt
B) d[C]/dt = −(3/2) d[B]/dt
C) d[C]/dt = −(2/3) d[B]/dt
E) d[C]/dt = (2/3) d[B]/dt*

**Solution:** When we are given an equation, we can write the rate expression in terms of appearance of products and disappearance of reactants.

The rate expression for the equation give would be:

Rate = -Δ__[A]__ = __-1 __Δ__[B]__ = __1 __Δ__[C]__

Δt 3 Δt 2 Δt

Therefore __-1 __Δ__[B]__ = __1 __Δ__[C]__

3 Δt 2 Δt

Rate of appearance of C is __ __Δ__[C]/__ Δt

Δ[C]/ Δt = -2/3Δ__[B]/__ Δt Choice C