14.1-14.3 Quiz

What factors affect rates of reactions?

reactant concentration, temperature, action of catalysts, physical state (surface temperature)

Rate of Reaction

change in concentration over time

rate of reaction of appearance equation

(change in moles)/(change in time)

rate of reaction of disappearance equation

-(change in moles)/(change in time)

What is the most useful unit for rate?

molarity; V is constant; M and mol are directly proportional

units for average rate

mol/L*s or M/s

Average rate of disappearance of reactant _____ over time

decreases

General Rule for Reaction Rate Stoichiometry

*don’t have coefficients in the denominator for the notable one

In general, rates increase as concentrations

increase

as [NH₄⁺] doubles with [NO₂^-] constant, the rate

doubles

as [NO₂^-] doubles with [NH₄⁺] constant, the rate

doubles

Rate Law for the reaction

Rate = k[NH₄⁺][NO₂^-]

k in rate law

rate constant; specific reaction, units based on overall order of reaction, not change with concentration or time, refers to temperature (changes with temp), depends on catalyst presence, determined experimentally

Rate Law

Rate = k[reactant 1]^m[reactant 2]ⁿ

Overall order of reaction

m+n+…

m and n mean in Rate Law

order in the specific reactant

when m or n =1, the rate is _______ _________ to the concentration of the reactant

directly proportional

when m or n =2, the rate is _________ __________ to the square of the concentration of that reactant

directly proportional; a reaction is xth order if doubling the concentration causes a 2x increase in rate

when m or n = 0, the rate _______ depend on the concentration of that reactant

does not

Units of rate constant general formula

units of rate/ units of concentration

1st order overall, k =

time^-1

2nd order overall, k =

M^-1time^-1

3rd order overall, k =

M^-2time^-1

How do you interpret a rate expression?

make a relationship; the rate of disappearance of reactant is equal to _____ (ex. twice) the rate of appearance of product

Orders

0,1,2,3,etc.; come from experimental data; not related to Stoichiometry; usually variable m or n; exponent of substance concentration