IC5.7.4 Reading pH curves © Oxford University Press Reading pH curves

IC5.7.4 Reading pH curves © Oxford University Press These diagrams show typical pH curves involving a strong acid, such as hydrochloric acid, and a strong alkali, such as sodium hydroxide solution. In each case, the conical flask contained 25 cm 3 and the burette delivered a total of 50 cm 3. volume of alkali (cm 3 )

IC5.7.4 Reading pH curves © Oxford University Press  Notice in both curves that the pH changes only gradually at first and at the end.  The end point of the reaction is when the acid and alkali exactly neutralise each other. There is a sudden change in pH at the end point.  These pH curves can be used to determine the volume of acid or alkali at the end point, and the pH when different amounts of acid or alkali are added. volume of alkali (cm 3 )

IC5.7.4 Reading pH curves © Oxford University Press 1.What was the pH of the alkali at the start?  pH 13 Use this graph to answer the following questions:

IC5.7.4 Reading pH curves © Oxford University Press 2.What was the pH of the mixture after 30 cm 3 of acid had been added?  pH 2

IC5.7.4 Reading pH curves © Oxford University Press 3.What volume of acid was needed to exactly neutralise the alkali?  25 cm 3

IC5.7.4 Reading pH curves © Oxford University Press 1. What was the pH of the mixture when 10 cm 3 of alkali had been added?  pH 1.2 Use this graph to answer the following questions: volume of alkali (cm 3 )

IC5.7.4 Reading pH curves © Oxford University Press 2.What volume of alkali was needed to reach a pH of 11.5?  30 cm 3 volume of alkali (cm 3 )

IC5.7.4 Reading pH curves © Oxford University Press 3.What was the total volume of the mixture at the end point?  75 cm 3 volume of alkali (cm 3 )