5.1.2: Concentration-time graphs

Question 1

What is the half-life of a reactant?

Answer 1

The time taken for the concentration of the reactant to reduce by half.

Question 2

Chemists can use many experimental techniques to measure concentrations of reactants or products in a reaction.
For reactions involving acids or bases we can measure…

Answer 2

• pH changes by carrying out titrations.

- pH changes by using a pH meter

Question 3

Chemists can use many experimental techniques to measure concentrations of reactants or products in a reaction.
For reactions involving gases we can measure…

Answer 3

• Change in volume or pressure

- The loss of mass in reactants

Question 4

Chemists can use many experimental techniques to measure concentrations of reactants or products in a reaction.
For reactions involving visual changes we can measure…

Answer 4

• The formation of a precipitate

- A colour change

Question 5

Why are visual changes to measure the concentration of products and reactants usually monitored using a colorometer?

Answer 5

-The intensity of colour is directly related to the concentration of a coloured substance.

Question 6

How can you determine the order of a reaction by looking at the half-life on a concentration-time graph?

Answer 6

-A first order reaction produces a constant half-life.

Question 7

How can the rate constant be determined by using the value of the half-life in a first order reaction?

Answer 7

k=ln(2)/t (subscript 1/2)