Reaction Rates

Question 1

What equation is used to calculate rate?

Answer 1

Change in concentration/ time

Question 2

What is the units for rate of reaction?

Answer 2

Mol dm ^-3 / s^-1

Question 3

What must particles do in order to react?

Answer 3

Collide with sufficient energy ( activation energy)

Correct orientation.

Question 4

Do most collisions result in a reaction?

Answer 4

No

Question 5

What are e the factors that affect rate of reaction?

Answer 5

Temperature 
Pressure
Concentration 
Surface area 
Catalyst

Question 6

What is the effect of increasing temperature on rate of reaction?

Answer 6

Increasing temperature
Increased rate
Much higher proportion of particles have energy greater than or equal to activation energy
Higher frequency of collisions per second

Question 7

What is the effect of increasing concentration or pressure of a gas on rate and why?

Answer 7

Increased rate
More particles in a given volume
More frequent successful collisions

Question 8

What are the variables in an experiment that can be monitored to calculate RoR?

Answer 8

Concentration of reactant or product
Gas volume of products
Mass substances of products

Question 9

How to calculate rate from a concentration time graph

Answer 9

Draw a tangent
Work out the gradient of the tangent
Use values as far apart on the line as possible

Question 10

What is a catalyst?

Answer 10

A substance which increases the rate of reaction but is not used up in the reaction

Question 11

How do catalyst work and how do they increase the rate of reaction?

Answer 11

They provide an alternate reaction pathway with a lower activation energy
Therefore more particles have energy greater than or equal to the activation energy
So more frequent successful collisions so increased rate

Question 12

What does a homogenous catalyst mean?

Answer 12

A catalyst in the same phase as the reactants

Question 13

What does heterogenous catalyst mean?

Answer 13

Catalyst used in the reaction is in a different phase to the reactants

Question 14

What are catalytic converters

Answer 14

They are present in vehicles to reduce toxic emission and prevent photochemical smog.

Question 15

Define activation energy

Answer 15

The minimum energy particles must collide with for a reaction to occur

Question 16

Name some important features of Boltzmann distribution

Answer 16

Area under the curve iequals total number of molecules
Area under curve does not change when conditions alter
The curve starts at origin
Curve does not touch or cross energy axis
Only molecules with energy greater than or equal to activation energy can react
Number of molecules is y axis
Energy is x axis

Question 17

What are the stages of catalysis?

Answer 17

One of the reactants approaches the catalysts surface and settles onto the active site - adsorption
Another reactant approaches the catalyst
Re arrangement of electron takes place- reaction
The products are released from the surface - desorption.