Video Transcript
Which of the following statements
best defines the rate of a chemical reaction? (A) The measure of change in the
concentration of the reactants or products per unit of time. (B) The difference in mass between
the reactants and the products. (C) The final concentration of the
products following a chemical reaction. (D) The speed at which particles
need to move in order to successfully collide. (E) Time at which the concentration
of the products and reactants are equal.
The rate of a chemical reaction
tells us its speed, in other words whether the reaction will be fast or slow. To define this quantity, we should
know that a rate in general is a change in some quantity per unit time. For example, the rate or speed of a
car is the change in distance per unit time. But during a chemical reaction,
it’s not the distance that’s changing. It’s the amount of the reactants
and products. Over time, the amount of reactants
decrease as they’re used up. And the amount of the products
increases as they’re formed. We can measure this amount as a
volume, a mass, or a concentration. But the most common measure is
probably the concentration of the reactants and products. Given what we’ve talked about,
answer choice (A) seems to best define the rate of a chemical reaction: the measure
of change in the concentration of the reactants or products per unit of time.
