rate law

what are rates of reactions

reactions, where some sort of change occurs, and how long it occurs for

what are the two ways to express the rate of a reaction?

• the rate of disappearance of the reactants

• the rate of formation of the products

rate law equation

rate = k[A]^m[B]ⁿ

rate law constant k

• specific to the reaction occurring

• depends on temperature, diff temp tiff constant

• does not depend on pressure

• small k means slow reaction

• large k means fast reaction

rate law exponents m and n

• do not change with temperature

• determined experimentally

• usually integers, most commonly 1 and 2

• 0, 3, and fractions are possible

• m and n values correspond to the coefficients of ONLY the rate determining step

overall order of a reaction/reaction order

• sum of individual exponents of each reactant in the rate law

• similar to polynomials, first, second, and third order reaction determined by overall order

rate of disappearance and (-)

rate of disappearance accounts for the - symbol, so you will not have a -rate of disappearance

why is k not affected by pressure?

pressure affects concentration because altering pressure changes volume

reactant order one

• double concentration = rate x 2¹ = doubles

• triple concentration = rate x 3¹ = triples

• linear

reactant order two

• double concertation = rate x 2² = quadruples

• triple concentration = rate x 3² = 9 times bigger

• square

reactant third order

• double concentration = rate x 2³ = 8x bigger

• triple concentration = rate x 3³ = 27x bigger

zero order reaction

• when the overall order is zero

• rate of reaction is a constant

• the rate of the reaction becomes independent the concentration of the reactant