chapter 10

Question 1

what is meant by rate of reaction

Answer 1

• how fast the reactants are used up or how fast the products are formed

Question 2

explain a concentration - time graph

Answer 2

• the gradient of the curve shows the rate of reaction
• the slope is steepest at the start as the reaction rate is the quickest
• the curve becomes less steep as the reaction progresses

Question 3

what factors can alter the rate of reaction

Answer 3

• concentration
• temperature
• use of a catalyst
• surface area of solid reactants

Question 4

what is meant by collision theory

Answer 4

• for a reaction to occur, the reactant molecules must come together and collide with the correct orientation and an energy greater than the activation energy

Question 5

what happens when you increase the concentration

Answer 5

• at low concentrations = less particles in a given area meaning that there are less frequent collisions and a slower rate of reaction
• at higher concentrations = more particles in a given volume meaning there are more successful collisions and a faster rate of reaction

Question 6

what happens when you change the pressure of a gas

Answer 6

• the gas molecules become closer together at higher pressures meaning that there are more successful collisions and a higher rate of reaction

Question 7

how can you measure the progress of a reaction

Answer 7

• monitoring the removal of a reactant
• following the formation of a product

Question 8

what does a catalyst do

Answer 8

• its a substance that increases the rate of reaction without undergoing any permanent changes
• it is not used up in the reaction
• it may react with the reactant to form an intermediate ora surface for the reaction to take place on
• at the end of the reaction it is always regenerated
• it provides an alternative reaction pathway with a lower activation energy

Question 9

what is a homogeneous catalyst

Answer 9

• it has the same physical state as the reactants

Question 10

what is a heterogeneous catalyst

Answer 10

• it has a different physical state to the reactants
• the molecules form weak bonds with the catalyst surface (adsorption)
• ## the bonds with the reactant molecules break