reaction rates

Question 1

What is the equation to calculate the rate

Answer 1

Rate = change in concentration / time

Question 2

What is the unit for the rate of reaction

Answer 2

mol dm-3s-1

Question 3

What must particles do in order to react?

Answer 3

Collide with sufficient energy (activation energy) and the correct orientation

Question 4

What are the factors that affect the rate of reaction

Answer 4

1. Temperature
2. Pressure
3. Concentration
4. Surface area
5. Catalyst

Question 5

Explain what the effect of increasing temperature is on the rate of reaction

Answer 5

• Increasing temperature increases the rate of reaction
• A much higher proportion of particles have energy greater than the activation energy
• Many more successful collisions per second
• Increased rate of reaction

Question 6

Explain the effect of increasing concentration/pressure on the rate of reaction

Answer 6

• Increasing concentration/pressure increases the rate of reaction
• There are more particles in a given volume
• More frequent collisions

Question 7

What are the variables in an experiment that can be monitored to calculate the rate of reaction

Answer 7

• Concentration of reactant or product
• The gas volume of products
• Mass of substances formed

Question 8

Define catalyst

Answer 8

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

Question 9

How do catalysts work and how do they increase the rate of reaction

Answer 9

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

Question 10

What does homogenous catalyst mean

Answer 10

A catalyst that is in the same phase (state) as the reactants

Question 11

What does heterogeneous catalyst mean

Answer 11

Catalyst used in the reaction is in a different phase (state) to the reactants

Question 12

What is a catalytic convertor

Answer 12

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

Question 13

Define activation energy

Answer 13

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

Question 14

Name important features of Boltzmann distribution

Answer 14

• Area under the curve is the total number of molecules
• Area under the curve doesn’t change when conditions alter
• The curve doesn’t touch or cross the energy axis
• Only the molecules with energy greater than the activation energy can react

Question 15

What is the axis in a Boltzmann distribution

Answer 15

X-axis - energy

Y axis - number of molecules with a given energy

Question 16

What happens to the Boltzmann distribution curve when the temperature is increased

Answer 16

Pushes the curve to the right because the molecules have more kinetic energy which means they collide more often

Question 17

Describe how catalysts are good for industries

Answer 17

• The lower production costs

- Give you more products in a shorter time

Question 18

Describe how catalysts are good for environmental sustainability

Answer 18

• Using catalysts means lower temperature and pressure is used, so energy is saved which means less CO2 is released
• They can also reduce waste by allowing a different reaction to be used with a better atom economy

Question 19

What are the advantages of catalytic converters

Answer 19

Catalytic converters on cars are made from alloys of platinum, palladium and rhodium, these reduce the pollution released into the atmosphere by speeding up the reaction