Which unit can be used to express the rate of a reaction?
ml / s
ml / g
g / ml
ml / mol
s / ml

mL / s

Explanation:

1) The rate of reaction is a speed. It is defined as the change in amount per time unit.

2) In form of equation reaction rate = Δ amount / time

3) Usually, it is more interesting to express the reaction rate in terms of the change of concentration, which is

reaction rate = Δ concentration / time

In those cases, the concentration is expressed in molar units per liter, so the rate is expressed as:

M / s = [mole/liter] / s

Which is what we usually find, but it is not mandatory.

4) So, other units can be used, like moles or volume (even pressure) to express the amount of a spices.

5) That is why rate of reation can be expressed as mL / s (mililiters per second).