C5b

rate of reaction

how quickly reactants are used or products are formed

• fast = high #

RoR equation

amount of reactant used / amount of product formed (unit g)

divided by

time taken

collision theory

particles must collide with enough energy & in the correct orientation to react successfully

change in temperature

increase: reactant particles move faster, more KE than Ea

• collide more often with more force = greater freq of success

• RoR increase

change in pressure

volume decreases(particles the same)

• crowded particles likely to collide more often

• greater freq. of successful collisions

• RoR increase

changing solution conc

more reactant particles in a fixed volume

• crowded particles likely to collide more often

• greater freq. of successful collisions

• RoR increase

adding a catalyst

RoR increases, yield remains unchanged

• nothing changes about the catalyst post-reaction

• solid catalysts need a larger surface area to catalyze faster

changing surface area in reaction

smaller pieces of the same mass will have a larger surface area

• more particles at surface = more exposed to react

RoR gas product measuring equipment

collecting gas formed in gas syringe over time

calculated mean rate up until a given time

calculate rough gradient with RATs

• (sometimes the phrase after is used. representing how much time has passed)

mean RoR between times

1. Calculate change in volume & time. (change y-axis = vol // change x-axis= time)

2. Insert change into gradient equation

mean RoR AT a specific time

draw tangent line, balanced on either side when the tangent stops touching the curve

reversible reactions

chemical reaction that can proceed in either direction

• products can also react to form the reactants

dynamic equilibrium

rate of forward reaction (equal to rate of reverse reaction)

• mass of reactants/products don’t have to be equal but do not change

dynamic equilibrium (3 marks)

1. conc of reactants & products do not change

2. ONLY occurs with reversible reactions in closed system

3. rate of forward = rate of reverse

equilibrium position

gives an idea of comparative amounts of reactants to products

• if lying to the left = reactant conc > product conc

equilibrium position temp

decrease in temp shifts eqp in exothermic direction, vice versa for endothermic

• a negative kJ/mol is exothermic

• this occurs to counteract the change

equilibrium position conc

if conc of substance is increased, eqp moves in direction away from substance & vice versa

equilibrium position pressure

increasing the pressure of a system with gases present will shift the equilibrium to the side with fewer molecules of gas

haber process equation

N₂ + 3H₂ ⇌ 2NH₃

why is an iron catalyst used?

lowers Ea, so lower temp can be used while RoR increases

• cost-effective

why is 450c used in the haber process?

• low temp needed to favor forward reaction

• high temp needed to increase Ke for collisions

why is 200 atm used?

high pressure » equilibrium to the right from increased collisions

• may have high costs and safety concern so 200 is a compromise