Question

A chemist needs to find the concentration of a solution of barium hydroxide.

Barium hydroxide solution is an alkali.

The chemist could find the concentration of the barium hydroxide solution using two different methods.

Method 1

• An excess of sodium sulfate solution is added to 25 cm3 of the barium hydroxide solution. A precipitate of barium sulfate is formed.

• The precipitate of barium sulfate is filtered, dried and weighed.

• The concentration of the barium hydroxide solution is calculated from the mass of

barium sulfate produced.

Method 2

• 25 cm3 of the barium hydroxide solution is titrated with hydrochloric acid of known concentration.

• The concentration of the barium hydroxide solution is calculated from the result of the titration.

Compare the advantages and disadvantages of the two methods. -5

Answer 1

Method 1: gravimetry

advantages: Impurities in the sample can be identified

disadvantages: The process is long, because it goes through several stages

Method 2: titration

advantages: the process is fast, because the titrate and titrant react immediately

disadvantages: Sometimes the determination of the end point of the titration is carried out too fast or too slowly so that the calculations carried out are inaccurate