Introduction to rates and rate laws
Kinetics is a study of the factors affecting the rate of a reaction.
The rate of reaction is equal to the change in concentration of a reactant or product, divided by the time taken for reaction and the coefficient of the substance in the balanced equation. The negative change in concentration of a reactant is used so that rate is always positive.
The differential rate law (equation) is the mathematical relationship between rate and the concentration of substances upon which rate depends.
General form of differential rate law: rate = k[A]x[B]y.
The order of a reaction in a substance is given by the exponent on its concentration.
The overall reaction order is given by the sum of the exponents.
A reaction with the rate law above is x order in A, y order in B and x+ y order overall.
The rate of reaction is equal to the change in concentration of a reactant or product, divided by the time taken for reaction and the coefficient of the substance in the balanced equation. The negative change in concentration of a reactant is used so that rate is always positive.
For aA + bB 
cC + dD
A, B, C and D are substances.
a, b, c and d are coefficients.
cC + dDA, B, C and D are substances.
a, b, c and d are coefficients.
| reaction rate = | - Δ[A] | = | - Δ[B] | = | Δ[C] | = | Δ[D] |
| a × Δt | b × Δt | c × Δt | d × Δt |
The differential rate law (equation) is the mathematical relationship between rate and the concentration of substances upon which rate depends.
General form of differential rate law: rate = k[A]x[B]y.
x and y are experimentally determined.
k, the rate constant, is constant for a reaction at a temperature.
k, the rate constant, is constant for a reaction at a temperature.
The order of a reaction in a substance is given by the exponent on its concentration.
The overall reaction order is given by the sum of the exponents.
A reaction with the rate law above is x order in A, y order in B and x+ y order overall.
If x is 1, then it is first order in A.
If y is also 1, it is first order in B, and the reaction is overall second order.
If y is also 1, it is first order in B, and the reaction is overall second order.