The Rate and Extent of Chemical Changes

Question 1

How can the rate of a chemical reaction be found?

Answer 1

By measuring the quantity of a reactant used or the quantity of a product formed over time.

Question 2

How do we calculate the overall rate of reaction from a graph?

Answer 2

Total quantity of reactant used/Total quantity of product formed ÷ total time taken. ( △y ÷ △x )

Question 3

How do we calculate the initial rate of reaction from a graph?

Answer 3

Draw a tangent to the line of best fit, starting at (0,0).

Then △y ÷ △x.

Question 4

How do we calculate the rate of reaction at a specific point on a graph? (e.g. at 210 seconds)

Answer 4

Draw a tangent to the line of best fit at that point.

Then △y ÷ △x.

Question 5

What units do we use to measure the quantity of a reactant used or product produced?

Answer 5

-Mass in grams

-Volume in cm³

Question 6

What are the units for a rate of reaction?

Answer 6

• g/s
• cm³/s

-mol/s

Question 7

How do you convert from grams to moles?

Answer 7

-Find the molar mass of the substance you are analysing

-Mol = mass ÷ Mr

Question 8

In graphs showing the quantity of product formed/ the quantity of reactant used up, against time, what goes on the x-axis?

Answer 8

Time (s)

Question 9

In graphs showing the quantity of product formed/ the quantity of reactant used up, against time, what goes on the y-axis?

Answer 9

The name of the product formed/ reactant used (cm³ or g)

Question 10

What is the slope of a linear graph?

Answer 10

A measure of its steepness/The gradient.

Question 11

What can we use on a graph to measure the rate of change?

Answer 11

The slope (gradient) of the tangent to a curve.

Question 12

What does the collision theory state?

Answer 12

Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

Question 13

Activation energy

Answer 13

The minimum amount of energy that particles must have to react.

Question 14

Give four ways in which we can measure the rate of a chemical reaction.

Answer 14

-Measure the loss in mass, per minute

-Count the number of bubbles, per minute

-Measure the volume of gas collected in a syringe after 1 minute

-Measure the time it takes for an ‘x’ placed under a flask to disappear when viewed through the rection mixture

Question 15

What is a posh way of saying that the cloudiness of a solution changes?

Answer 15

Its ‘turbidity’ changes.

Question 16

Why might the mass of a reaction mixture decrease?

Answer 16

Due to gas given off.