rate equations and Kp

Question 1

Define rate of reaction:

Answer 1

The change in concentration of a substrate in unit time

Question 2

What are the units of rate of reaction?

Answer 2

mol dm^-3 s^-1

Question 3

What are the three factors that affect rate of reaction?

Answer 3

Temperature, concentration of reagents, presence of a catalyst

Question 4

At a fixed temperature, where is the rate of reaction at its greatest?

Answer 4

At the start of a reaction, because the concentration of the reactants is greatest

Question 5

How is rate affected as the reaction proceeds?

Answer 5

The concentration of the reactants decreases and therefore the rate falls

Question 6

What is the general rate equation?

Answer 6

Rate= k [A]^m [B]^n

Question 7

What is k in the context of rate equations?

Answer 7

k is the rate constant. k varies depending on the type of reaction taking place

Question 8

What is order?

Answer 8

Order is the power to which the concentration term is raised in the rate equation

Question 9

How does temperature affect the rate constant?

Answer 9

Rate constant varies exponentially with temperature

Question 10

Describe the relationship between concentration of reactant and rate in a zero order reaction:

Answer 10

Rate of reaction is unaffected by concentration of the reactant, and rate will be constant throughout the reaction

Question 11

What are the units of k in a zero order reaction?

Answer 11

mol dm^-3 s^-1

Question 12

What is the relationship between concentration of reactant and rate if the reaction is 1st order?

Answer 12

If concentration of a reactant changes by a factor, the rate will change by the same factor

Question 13

What are the units of k in a first order reaction?

Answer 13

s^-1

Question 14

What is the relationship between concentration of reactant and rate if the reaction is 2nd order?

Answer 14

If concentration of a reactant increases by a factor then the rate of reaction will increase by the square of that factor

Question 15

What are the units of k in a second order reaction?

Answer 15

mol^-1 dm^3 s^-1

Question 16

How is rate of reaction found using a graph?

Answer 16

The rate at a particular time is found by measuring the gradient at that time

Question 17

What is the initial rate?

Answer 17

The rate at the start of reaction when the initial concentrations of the reagents are known.

Question 18

How can the rate equation be determined?

Answer 18

By studying the effect on the initial rate of changes in the initial concentrations of reagents

Question 19

What is the rate determining step?

Answer 19

The slowest step in a reaction involving multiple steps. Species in the rate equation must be found in the rate determining step

Question 20

How is a catalyst represented in a reaction?

Answer 20

The catalyst will appear in the rate equation, but not in the overall chemical equation

Question 21

What does the Arrhenius equation link?

Answer 21

Links rate constant, the temperature and the activation energy

Question 22

What are the two Arrhenius equations?

Answer 22

k=A e^(-Ea/RT)

lnk=-Ea/RT + lnA

Question 23

What is Kp?

Answer 23

Kp is the equilibrium constant for a system at equilibrium where all reactants and products are in the gaseous state

Question 24

How is Kp calculated?

Answer 24

First calculate mole fraction:
moles of each reactant/ total moles of gas in the mixture

Multiply mole fraction by the total pressure of the reaction to find partial pressure

Kp= (pC)^c / (pA)^a (pB)^b