kinetics II

Question 1

Name six ways to obtain the rate of reaction

Answer 1

• titration
• colorimetry
• mass change
• volume of gas evolved
• ph change
• electrical conductivity

Question 2

obtaining rate of reaction: titration

Answer 2

• take small samples of a solution at regular intervals + titrate using standard solution ( quench using deionised water )
• rate found by measuring change in conc of products/reactant over time

Question 3

obtaining rate of reaction: colorimetry

Answer 3

• use a calorimeter (higher conc of colour of the solution=higher absorption by the calorimeter)
• plot known conc of coloured solution against absorbance
• convert absorbance at each time into concentration

Question 4

obtaining rate of reaction: volume of gas evolved

Answer 4

• collect gas in a gas syringe + record how much you have at regular time intervals
• use ideal gas equation + molar ratio

Question 5

obtaining rate of reaction: mass change

Answer 5

• gas given off, system loses mass
• use moles to calculate how much gas lost and how much reactant left

Question 6

obtaining rate of reaction: PH change

Answer 6

• reaction uses or produces H+ –> PH changes
• measure pH of solution at regular intervals + calculate conc of H+ (using pH meter)

Question 7

obtaining rate of reaction: electrical conductivity

Answer 7

• if number of ions changes so will electrical conductivity

Question 8

what is the rate of reaction

Answer 8

change in the mount of reactants or products per unit time (amount of reactants or products made/time (s))

Question 9

what is the rate equation and its units

Answer 9

rate equation= K[A]^a[B]^b
Moldm-3S-1

Question 10

what occurs with an increase in temperature regarding the rate equation

Answer 10

• value of K increases (rate constant)
• particles have more energy, higher frequency of collisions. rate increases

Question 11

what does not change with an increase in temperature regarding the rate equation

Answer 11

concentration of substances

Question 12

what is zero order

Answer 12

change in concentration has no effect on rate

Question 13

what is first order

Answer 13

change in concentration has proportional effect on rate

Question 14

what is second order

Answer 14

change in concentration has squared proportional effect on rate (2A=4R)

Question 15

what is an SN1 mechanism

Answer 15

1 molecule/ion in the rate determining step

Question 16

what is an Sn2 mechanism

Answer 16

2 molecules or ions in the rate determining step

Question 17

which haloalkanes correspond to Sn1 or Sn2

Answer 17

primary –> Sn2
secondary –> Sn2 + Sn1
tertiary –> Sn1

Question 18

Write down the Arrhenius Equation

Answer 18

K= Ae^Ea/RT
Ae= arrhenius constant

Question 19

arrhenius equation. decrease in Ea=

Answer 19

increase in K ( rate constant )
–> rate of reaction increases, more particles have sufficient energy to react when they collide

Question 20

arrhenius equation, increase in T=

Answer 20

increase in K
–> particles have more kinetic energy, more likely to collide with at least the activation energy. rate of reaction increases