chap 17 rate of reactions

Question 1

how can rate of reaction be measured (3)

Answer 1

measuring time for reaction to be complete, measuring amount of product formed over a period of time, measuring how much reactant is used up over a period of time

Question 2

how to calculate average rate

Answer 2

total volume of products/total time taken

Question 3

when does effective collisions occur

Answer 3

when the reactant particles collide with energy greater than or equal to the activation energy

Question 4

what are the factors affecting rate of collision (5)

Answer 4

particle size of solid reactant, concentration of solution, pressure of gases, temperature, addition of catalyst

Question 5

the smaller the particle size,
(2)

Answer 5

the larger the surface area to volume ratio, the higher the frequency of collision and therefore, higher frequency of effective collision between particles, rate of reaction is higher

Question 6

the higher the concentration of the reactants,
(2)

Answer 6

the larger the number of particles per unit volume, the higher the frequency of collisions, therefore higher frequency of effective collisions between particles. rate of reaction is higher

Question 7

at a higher pressure,
(2)

Answer 7

the particles are closer together, therefore is a higher frequency of collisions, therefore higher frequency of effective collisions between particles and higher rate of reaction

Question 8

at a higher temperature,
(2)

Answer 8

the particles have higher kinetic energy and move faster, resulting in higher the frequency of collisions. there are more particles with energy greater than or equal to the activation energy. all these result in higher frequency of effective collisions and higher rate of reaction

Question 9

function of a catalyst

Answer 9

it increases the rate of chemical reactions and remains chemically unchanged at the end of the reaction

Question 10

how does catalyst work (4)

Answer 10

catalyst provides an alternative pathway of a lower activation energy for reactions to occur. in the catalysed pathway, activation energy is lower, therefore more particles have energy more than or equal to the activation energy. this increases the frequency of effective collisions and rate of reaction