Reaction Kinetics

Question 1

Units for rate of reaction:-

Answer 1

moldm^-3 s^-1 (or min^-1 if reaction is slower)

Question 2

Relative to moles:-

Answer 2

In N2 + 3H2 -> 2NH3

If N2 rate of loss is 1moldm^-3 min^-1, H2 rate will be 3moldm^-3 min^-1

Question 3

Rate from graph:-

Answer 3

Tangent and calc gradient on conc v time graph.

Question 4

Experimental methods:-

Answer 4

Continuous monitoring of a changing property.

Question 5

Continuous monitoring examples (4):-

Answer 5

• mass
• volume of gas evolved
• pH
• colorimetry if colour change

Question 6

Rate equation:-

Answer 6

For xA+ yB -> products-
Rate = k[A]^m [B]^n
M = order for A
N = order for B.

Question 7

Order of reaction:-

Answer 7

The power to which the conc is raised in the rate equation.

Question 8

Overall order of reaction:-

Answer 8

M + n

Question 9

Rate constant:-

Answer 9

K, is a meaure of the probability that a reaction will happen when the particles collide.

Question 10

K value change:-

Answer 10

Increases as temp increases because a greater proportion of reactant molecules exceed the activation energy. Other variables don’t affect. May increase w/ catalyst, but whole rate equ often changes.

Question 11

K units:-

Answer 11

Mol^(1-x) dm^(3x - 3) s^-1.

X = overall order of reaction.

Question 12

Half life:-

Answer 12

Time taken for a reactant’s conc to half. Abbreviated to t 1/2.

Question 13

Zero order:-

Answer 13

A -> products. Rate = k[A]^0. Conc v time Graph = diagonal line w/ decreasing half lives. Rate = k.
Rate v conc graph = straight horizontal line.

Question 14

First order:-

Answer 14

Conc v time Graph = exponential decrease.
Rate v conc = upwards diagonal line as K directly proportional to conc.
Half lives same.

Question 15

Second order:-

Answer 15

Rate = k[A]^2.
Conc v time graph = exponential decrease with doubling half lives.
Rate v conc = exponential
Rate v conc^2 graph = diag line.

Question 16

K for first order:-

Answer 16

K= ln2/ t 1/2