Chem 111 test 1

chemical kinetics

studies reaction rates and mechanisms

rate

how much a quantity changes in a given period of time

rate of a chemical reaction

a change of concentration in a unit of time

what factors affect the rate of a chemical reaction?

temperature, concentration, surface area, pressure (for gases), and the presence of a catalyst

as time goes on, the rate of a reaction generally slows down because the concentration of reactants

decreases

at some time the reaction stops, either because the reactants ___ or the system has reaced equilibrium

run out

rate =

Δ[A]/Δt

what is ΔA?

change in molarity of A over time period

if Δ[A] > 0 then,

A is a product

if Δ[A], then A is a

reactant

rate of reaction is always…

defined as a positive quantity

How to determine reaction rate?

measure the concentration of a reactant or a product at different points in time

instantaneous rates

the value of a rate at a particular time

why are intial rates important?

reactions are reversible

rate law

shows how rate depends on concentration

rate law for aA + bB → cC +dD

rate = k[A]^x [B]^y

what is “k?'“

rate constant

the overall order of reaction is

sum of all exponents in the rate law

zero order

rate = k[A]^0f

first order

rate = k[A]¹

second order

rate = k[A]2

what’s the impact on rate when changing concentration for zero order?

none

what’s the impact on rate when changing concentration for first order?

rate changes by same factor as the concentration

what’s the impact on rate when changing concentration for second order?

rate changes by the square of the factor the concentration changes

integrated rate law for first order reaction

ln[A]_t=-kt+ln[A]₀

integrated rate law for second order reactions

1/[A]_t=kt+1/[A]₀

integrated rate law for zero order reactions

[A] = -kt+[A]₀