6. Chemical kinetics

Question 1

rate of reaction is

Answer 1

the speed at which reactants are used up or products are formed

Question 2

rate of reaction (c)

Answer 2

change in concentration of reactants or products per unit time

Question 3

rate of reaction at any time can be found from a graph of concentration against time by

Answer 3

drawing a tangent at the particular time and finding the gradient (slope) of the tangent

Question 4

successful collision according to the collision theory

Answer 4

• a collision must involve more than a certain minimum amount
of energy
• molecules must collide with the correct orientations

Question 5

factors affecting reaction rate

Answer 5

• concentration of reactants
• pressure for (reactions involving gases)
• surface area of solid reactants
• temperature
• catalysis

Question 6

boltzmann curve for lower and higher temperatures

Answer 6

Question 7

a catalyst is

Answer 7

a substance that increases the rate of a chemical reaction without itself being used up in the reaction

a catalyst acts by allowing the reaction to proceed by an alternative pathway of lower activation energy

Question 8

the rate equation is

Answer 8

an experimentally determined equation that relates rate of reaction to the concentrations of substances in the reaction mixture

Question 9

for W+X →Y+Z,

rate =

Answer 9

rate = k[W]^m[X]ⁿ

Question 10

the rate constant is

Answer 10

a constant of proportionality relating the concentrations in the experimentally determined rate equation to the rate of a chemical reaction

Question 11

the order of a reaction with respect to a particular reactant is

Answer 11

the power of the reactant’s concentration in the experimentally determined rate equation

Question 12

for a 0 order reaction

Answer 12

is not affected by concentration
rate equation = k
unit: mol dm^-3 s^-1

Question 13

first order reaction

Answer 13

rate is directly proportional to the concentration
rate equation= k[X]
unit: s^-1

Question 14

second order reaction

Answer 14

rate of reaction is proportional to concentration squared
rate=k[X]²
units: mol^-1dm³s^-1

Question 15

generally, units for k=

Answer 15

concentration^{(1−overall order)} time^-1

Question 16

rate determining step

Answer 16

slowest step

Question 17

as the temperature increases, the rate constant

Answer 17

increases exponentially
the Arrhenius equation can be used to model the variation of the rate constant with temperature

Question 18

compare arhenius equation with equation of a straight line

Answer 18