Monitoring reactions

Question 1

What is reaction rate?

Answer 1

The change in the amount of reactants or products per unit time

Question 2

What are the usual units for reaction rate?

Answer 2

mol dm-3 s-1

Question 3

What is continuous monitoring?

Answer 3

Following the reaction all the way through to its end by recording the amount of product or reactant you have at regular time intervals

Question 4

How can you measure the gas volume?

Answer 4

Collect in a gas syringe and record how much you’ve got at regular time intervals

Question 5

How do you use the gas volume to work out the rate of reaction?

Answer 5

Need to work out the concentrations of the reactants or products at each time point and then draw a time-concentration graph

Question 6

How could changes in pH tell you about the progress of a reaction?

Answer 6

Measure the pH of the solution at regular intervals and calculate the concentration of H+ ions

Question 7

How can you use colour change to measure the reaction rate?

Answer 7

Track the colour change using a colorimeter which measures the absorbance of the solution.
The more concentrated the colour of the solution, the higher the absorbance

Question 8

How can you use loss of mass to measure the reaction rate?

Answer 8

If a gas is given off, the system will lose mass and this can be measured at regular time intervals with a balance.
Then use mole calculations to work out how much gas you’ve lost and therefore how many moles of reactants are left