3.2.2 reaction rates

Question 1

describe the effect of concentration/pressure on rate of reaction

Answer 1

at higher concentrations/pressures there are more particles per unit volume and so the particles collide with a greater frequency and there will be a higher frequency of effective collisions

Question 2

describe the effect of temperature on rate of reaction

Answer 2

at higher temperatures the energy of the particles increases and they collide more frequently and more often with energy greater than the activation energy

Question 3

explain how catalysts speed up rate of reaction

Answer 3

catalysts lower Ea by providing a different pathway so more particles have energy above the Ea so more successful collisions occur

Question 4

what goes on the vertical and horizontal axis for an maxwell boltzmann distribution diagram

Answer 4

vertical- number of molecules with a given energy

horizontal- energy

Question 5

explain increases temperature in a maxwell boltzmann distribution diagram

Answer 5

causes a significantly larger proportion of particles to have energy greater than Ea so frequency of successful collisions increases

Question 6

how can you calculate reaction rates in a conc vs time graph

Answer 6

• draw a tangent to work out initial rate

- (rate) gradient=change in y / change in x

Question 7

heterogenous catalyst

Answer 7

different state from reactants usually solids whereas reactants are (aq) or (g), reaction occurs at surface of the catalyst

Question 8

homogenous catalyst

Answer 8

same state as reactants, reaction happens through an intermediate species

Question 9

describe benefits of catalysts

Answer 9

• speeds up rate of reaction
• lower temperatures and pressures can be used to save cost
• reduced energy demand -fewer CO2 emissions
• enables better atom economy so there is less waste, undesired products and hazardous products