Rate Law Expression

$$\text{Rate} = k \cdot [A]^x \cdot [B]^y \qquad n = x + y$$

Concept: Relates the rate of a chemical reaction to the molar concentrations of its reactants, where each concentration term is raised to a power determined experimentally.

Notation:

• $$\text{Rate}$$ = Speed of reaction ($$\text{M s}^{-1}$$);
• $$k$$ = Rate constant;
• $$[A], [B]$$ = Molar concentrations of reactants;
• $$x, y$$ = Order with respect to $$A$$ and $$B$$;
• $$n$$ = Overall order of the reaction.

Units of Rate Constant

$$\text{Units} = (\text{mol L}^{-1})^{1-n} \cdot \text{s}^{-1} \qquad \text{or} \qquad \text{Units} = (\text{atm})^{1-n} \cdot \text{s}^{-1} \text{ (for gases)}$$

Concept: Determines the dimensional units of the rate constant $$k$$, which vary systematically based on the overall reaction order.

Notation:

• $$n$$ = Overall order of the reaction;
• $$\text{mol L}^{-1}$$ = Molarity;
• $$\text{atm}$$ = Atmosphere pressure unit;
• $$\text{s}^{-1}$$ = Per second.