Kinetics

Question 1

What are the conditions for a collision to result in a reaction?

Answer 1

Correct reactant particles, correct orientation, sufficient energy

Question 2

5 factors that affect rate of reaction

Answer 2

Temperature, pressure, catalyst, concentration of solutions, surface area/particle size

Question 3

How increasing temp increases rate of reaction

Answer 3

Particles have more kinetic energy -> collide more frequently and each collision occurs with greater energy therefore greater proportion of collisions occur with required activation energy. More successful collisions.

Question 4

How increasing concentration increases rate of reaction

Answer 4

More reactant particles in given volume of solution. increases freq of collisions which increases successful collisions.

Question 5

Surface area increasing/particle size decreasing increases rate of reaction

Answer 5

For same mass of solid, smaller particles means more exposed reactant particles, increases freq of collisions between reactant particles which increases freq of successful collisions.

Question 6

How does catalyst increase rate of reaction

Answer 6

Provides alternative route for reaction with lower activation energy. Greater proportion of collisions will occur with required activation energy, increases successful collisions. CATALYST IS CHEMICALLY UNCHANGED.

Question 7

What is Ea

Answer 7

Activation energy: minimum energy which a collision between reactants requires for reaction to occur and products to be formed.

Question 8

How to find rate of reaction and units when no mass/volume given

Answer 8

rate of reaction = 1 / time taken for reaction to complete

Question 9

How to find rate of reaction with mass/volume

Answer 9

Amount of reactant / time taken

Question 10

How to work out reaction rate from graph

Answer 10

draw tangent

Question 11

Heterogenous catalyst

Answer 11

Different phase from reactants. Happens on surface of catalyst therefore increasing surface area of catalyst increases rate of reaction. Lowers activation energy

Question 12

Homogenous catalyst

Answer 12

Same phase as reactants. Normally aqueous among aqueous reactants. Reactants combine with the catalyst to make intermediate species which then forms product.

Question 13

What is Maxwell-Boltzmann distribution

Answer 13

Curve that shows few molecules move slowly, most molecules move at moderate speed and few molecules have over Ea.

Question 14

Industrial uses of catalyst

Answer 14

Lower production cost (less harsh environment making product), more product and better properties of product.

Question 15

How to draw Maxwell-Boltzmann curve

Answer 15

Draw normal distribution and then skew it left. When raising temp, lower the peak to the right and make the gradient smaller.

Question 16

Rate equation

Answer 16

Rate = k [A]^order * [B]^order

Question 17

What does 0 order mean in rate equation

Answer 17

Does not feature or affect rate.

Question 18

How to find overall order of reaction

Answer 18

Sum of all orders

Question 19

What is the rate constant dependent on?

Answer 19

Temperature

Question 20

What does a constant half life for concentration of reactant mean for order?

Answer 20

1st order

Question 21

What does a straight line for concentration of reactant mean for order?

Answer 21

0 order

Question 22

What is the slow step in the reaction?

Answer 22

Step that takes the slowest, RDS, all reactants in rate equation involved before or during it.

Question 23

How to obtain rate of reaction: titration

Answer 23

Take regular samples during reaction and quench. Measure conc. of reactants by titration.

Question 24

How to obtain rate of reaction: colorimetry

Answer 24

Tracks concentration of specific species with distinct colour. Amount of light absorbed proportional to the conc. of reactant.

Question 25

How to obtain rate of reaction: mass change

Answer 25

Can be used to measure mass of reaction when a gas is produced.

Question 26

How to obtain rate of reaction: volume of gas evolved

Answer 26

Measure volume of gas produced via gas syringe or collection over water

Question 27

Rate equation for SN1

Answer 27

Rate = k [Haloalkane]

Question 28

Rate equation for SN2

Answer 28

Rate = k [Haloalkane] [Nu:]

Question 29

When is SN1 fastest

Answer 29

When the carbocation intermediate is the most stable as it makes the slow step faster directly.

Question 30

Iodine clock reaction H2O2 + 2I- + 2H+ -> 2H2O + I2

Answer 30

Small amount of sodium thiosulfate solution and starch added to excess H2O2 and iodide ions in acid solution.
Any iodine that forms reactions with thiosulfate. When all thiosulfate reacted, mixture will turn blue-black as iodine in solution gone.
Time taken for reaction to occur and conc of reactants can give initial rate w.r.t reactant.

Question 31

0 order conc to time; rate to conc. of reactant shape

Answer 31

Constant gradient; horizontal line

Question 32

1 order conc to time; rate to conc. of reactant shape

Answer 32

Downwards curve constant half life; increasing rate with constant gradient

Question 33

2 order conc to time; rate to conc. of reactant shape

Answer 33

Downward curve, not constant half life; increasing rate with increasing gradient, but if plotted against conc. squared then constant gradient.

Question 34

Gradient of graph of ln(k) plotted against 1/T

Answer 34

-Ea / R in joules/mol