Several students titrate 25.00 cm3 samples of a standard solution of sodium carbonate, Na2CO3(aq)\text{Na}_2\text{CO}_3\text{(aq)}Na2CO3(aq), with hydrochloric acid, HCl(aq)\text{HCl(aq)}HCl(aq), using a burette.
One student obtains a smaller titre than the other students.
Which procedure explains this smaller titre?
The pipette is rinsed with deionised water but not with the Na2CO3(aq)\text{Na}_2\text{CO}_3\text{(aq)}Na2CO3(aq) solution before filling.
The conical flask is rinsed with the Na2CO3(aq)\text{Na}_2\text{CO}_3\text{(aq)}Na2CO3(aq) solution before the titration.
The burette is rinsed with deionised water but not with the HCl(aq)\text{HCl(aq)}HCl(aq) solution before filling.
An air bubble in the jet of the burette is dislodged and filled with acid during the titration.
5 exam-style questions on OCR A A Level Chemistry Use of apparatus and techniques. Each one has a worked solution and a mark scheme showing where the marks go.