13 Kinetics I

Question 1

What is a unimolecular reaction?

Answer 1

Reaction involving one starting molecule that can decompose into two or more molecules, or can isomerise into a different molecule

Question 2

what is a bimolecular reaction?

Answer 2

Reactions involving 2 molecules, where molecules are able to associate or exchange.

Question 3

What is a rate of reaction and how is it represented?

Answer 3

Rate of reaction shows an increase or decrease of concentration over time, and is given by dc/dt.

Question 4

What is k?

Answer 4

k is the rate constant, and shows us the rate of a specified chemical reaction at a set temperature. Units are given by the order of reaction.

Question 5

What is a pseudo-first order reaction?

Answer 5

When a reactant is present in such great excess that its concentration may be considered constant, or nearly so.

Question 6

What is a zero order reaction? what is the rate law?

Answer 6

A reaction where the rate depends only on time and is independent of concentration.
rate = -k

Question 7

What is the integrated rate equation for a zero order reaction? what does each component mean?

Answer 7

[A]t = [A]0 - k0t
The concentration of A at time t is equal to the initial concentration of A minus the rate, times t.
-k0 = slope
Slope is negaative because reactants are decomposing as the reaction goes on

Question 8

what is the half-life equation for zero-order reactions?

Answer 8

t1/2 = [A]0/2k0

Half life is equal to the initial concentration of A divided by 2 times the rate constant.

Question 9

How would a zero-order reaction be graphed? (axis labels, title, trend line)

Answer 9

X-axis: time
y-axis: concentration [A]
slope: -k0
trendline: linear decreasing
title: [A] vs t

Question 10

what is a first order reaction? what is the rate law

Answer 10

reactions where concentration is directly proportional to the rate.
rate = -k[A]

Question 11

What is the integrated rate equation for a first-order reaction?

Answer 11

ln[A]t = ln[A]0 - kt

Question 12

what is the half-life equation for a first-order reaction?

Answer 12

t1/2 = ln2/k –> 0.693/k

where k is found by plotting the slope.

Question 13

How would a first-order reaction be graphed? (axis, title, slope etc.)

Answer 13

title: ln[A] vs t
x-axis: time t
y-axis: ln[A]
slope= -k

Question 14

What is a second order reaction? what is the rate law?

Answer 14

A reaction where rate of which depends on concentrations of 2 compounds.
rate = -k [A]^2

Question 15

what is the rate equation for a second-order reaction?

Answer 15

1/[A]t = kt + 1/[A]0

Question 16

What is the half-life equation for a second-order reaction?

Answer 16

t1/2 = 1/k[A]0

Question 17

How is a second order reaction graphed? (axis, title, slope etc)

Answer 17

Title: 1/[A] vs t
x-axis: t
y-axis: 1/[A]
slope = k

Question 18

what is activation energy?

Answer 18

the minimum amount of energy required for a reaction to occur (Ea)

Question 19

What is Arrhenius’s equation?

Answer 19

k = Ae^(-Ea/RT)
k = reaction rate constant
A = frequency factor
Ea = activation energy
R = universal gas constant
T = absolute temp (K)

Question 20

what factors affect reaction rates?

Answer 20

temperature, concentration of reactions, solvents, catalysts