Rates of Reaction

Question 1

What is the rate of a reaction?

Answer 1

How fast the reactants are changed into products

Question 2

What is an example of a slow reaction?

Answer 2

Rusting of iron/ Chemical Weathering

Question 3

What is a moderate speed reaction?

Answer 3

Metal magnesium reacting with an acid

Question 4

What is an example of a fast reaction?

Answer 4

Burning,Explosions or Combustion

Question 5

What are the two general ways you could measure the rate of a reaction?

Answer 5

Measure the rate at which reactants are used up OR measure the rate at which products are made

Question 6

What does the tangent of a graph for a rate of reaction show?

Answer 6

How fast the rate of reaction is. The steeper the line in the graph, the faster the rate of reaction

Question 7

What are the five factors affecting reaction rate?

Answer 7

Concentration (of solutions)
Temperature
Surface Area (reactants in solid state)
Catalyst (presence of absence)
Pressure (for reactants in gaseous state)

Question 8

What does the collision theory state?

Answer 8

1)For a reaction to occur, REACTANT particles must collide with each other.
2)These collisions must be of sufficient energy, ie.collisions must be equal or greater than the Activation Energy if they are to lead to a successful reaction

Question 9

How do you speed up rates of reactions in terms of frequency of collisions?

Answer 9

If the frequency of collisions with greater than activation energy increases, the reaction rate will also increase

Question 10

What is meant by the term ‘Activation Energy’

Answer 10

The MINIMUM amount of energy required for a reaction to take place

Question 11

How does increasing the temperature increase the rate of reaction?

Answer 11

When the temperature is increased the particles gain energy in the form of kinetic energy. They therefore move around faster and collide more frequently.More collisions will reach activation energy so more successful collisions will occur.

Question 12

How does the concentration of a solution increase the rate of a reaction?

Answer 12

By increasing the concentration of reactants in solutions, the number of reactant ions within a certain volume is increased.Since there are more particles within the same volume, there are more frequent collisions and the rate of reaction increases.

Question 13

How does increasing the surface area increase the reaction rate?

Answer 13

Crushing up a solid into a powder increases its surface area to volume ratio.This means there is higher area of contact between the solid and the other reactant and more frequent collisions.

Question 14

What is a catalyst and how does it affect the rate of a reaction?

Answer 14

A catalyst is a substance that speeds up a reaction without being used up in the reaction. They increase the rate of reaction by providing an alternative route for the reaction that has a lower activation energy than the uncatalysed reaction.

Question 15

What are the three ways to measure the rate of a reaction?

Answer 15

Precipitation and Colour Change, Change in mass and Volume of gas given off

Question 16

How do you use precipitation being created to measure the rate of a reaction?

Answer 16

If the initial solution is transparent and the product is a precipitate, it will cloud the solution and it will become opaque.You can put a mark through the solution and measure how long it takes for the mark to disappear.The faster the mark disappears, the quicker the reaction.

Question 17

How do you use colour change to measure the rate of a reaction?

Answer 17

If the reactants are coloured and the products are colourless, you can time how long it takes for the solution to lose or gain colour.Results can be subjective however due to human error.

Question 18

How do you use a change in mass to measure the rate of a reaction?

Answer 18

A conical flask with your reactants is placed on top of a mass balance.A cotton wool plug is placed at the top of the conical flask to prevent the loss of mass due to acid spray but also to let the gas escape.Readings are taken every 10 seconds as the mass drops due to the loss of gas.

Question 19

How do you use Volume of Gas given off to measure the rate of a reaction?

Answer 19

Use a gas syringe or an upside down water filled measuring cylinder for water displacement. The acid is added, the bung quickly replaced and the volume of gas produced recorded every 10 seconds.

Question 20

What changed in hydrogen peroxide and manganese oxide experiment we did that allowed us to measure the rate of the reaction?

Answer 20

1)Measured the volume of gas given off at intervals of 5 seconds.

2)Changed the temperature of the solution and measured the change in mass.

Question 21

What changed in the hydrochloric acid and magnesium ribbon experiment that allowed us to measure the rate of the reaction?

Answer 21

We changed the concentration of the solution and measure the rate of the reaction by timing how long it takes to see how long the visible reaction lasts.

Question 22

What changed in the Hydrochloric acid and marble chip experiment and how were we able to measure the rate of the reaction?

Answer 22

Changed the surface area of the solids to increase the rate of reaction and measure the rate of reaction by measuring the volume of gas lost every 10 seconds.

Question 23

What did we change in the sodium thiosulphate and hydrochloric acid (the disappearing cross) experiment and how did we measure the rate of the reaction?

Answer 23

Changed the temperature to increase the rate of the reaction and measured the rate by doing 1000/Time (in seconds) and the colour change of the solution

Question 24

What are enzymes?

Answer 24

They are biological catalysts used in fermentation.