rates

Seite 1

RATES

EFFECT ON RATE - CATALYSTS

increase both forward and backward reactions

no effect on rate

EFFECT ON RATE - TEMPERATURE (increase in temp.)

for an endothermic reaction, shift rightwards, more products, Kc increase

for an exothermic reaction, shift leftwards, more reactants, Kc decrease.

EFFECT ON RATE - CONCENTRATION

increase reactants, shift leftwards, forward reaction favoured, more products made (ALSO LESS PRODUCTS IN THE SYSTEM)

increase products, shift rightwards, backward reaction favoured, less products made (ALSO LESS REACTANTS IN THE SYSTEM)

RATE EQUATIONS

X + Y => Z is useless

rate = k[X]^m[Y]^n

k ~> rate constant

[X] ~> conc. of substance X

[Y] ~> conc. of substance Y

m ~> the order with respect to X

n ~> the order with respect to Y

m+n ~> overall order of the reaction

MEASURING REACTION RATES

COLORIMETRY - measures the intensity of a colour in a reaction mixture with time; this can only be used if a colour change occurs

MASS CHANGE - measures the change in mass due to a gas(es) being produced

VOLUME CHANGE - measures the volume change due to a gas(es) being produced

TITRIMETRIC ANALYSIS - uses titration to measure changing concentration of a reactant or product

New Page