Chemical Kinetics Practice Test

What is the reaction rate?

The product of concentrations The change in concentration of a reactant or a product per unit time The equilibrium constant The energy change per mole

Correct Answer:

The change in concentration of a reactant or a product per unit time

Explanation:

Reaction rate is the speed at which a reaction proceeds, i.e., how fast concentrations change with time. It’s defined as the change in concentration of a reactant (negative sign) or a product (positive sign) per unit time. For a simple reaction A → products, the rate can be written as rate = -d[A]/dt = d[Product]/dt. The usual units are molarity per second (M/s). Rate can be described as an average rate over a time interval or as an instantaneous rate at a particular moment. The other ideas describe different things: the product of concentrations isn’t the rate itself, the equilibrium constant tells how far the reaction goes at equilibrium, and the energy change per mole is a thermodynamic property, not the speed of the reaction.

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