Titration

Question 1

During a titration, a chemist rinsed the inside of the conical flask with deionised water. The water used for rinsing remained in the conical flask.
Give one reason why this rinsing can improve the accuracy of the end-point.

Answer 1

Returns reagent on the sides of the flask to the reaction mixture (to ensure that all of the acid / alkali reacts)

Question 2

Suggest one reason why a 250 cm3 conical flask is preferred to a 250 cm3 beaker for a titration.

Answer 2

Less chance of losing liquid on swirling / liquid doesn’t splash on swirling

Do not accept ‘easier to swirl’ on its own

Question 3

The correct technique can improve the accuracy of a titration.
State why it is important to fill the space below the tap in the burette with solution A before beginning an accurate titration.

Answer 3

Space will fill during titration / titres or volumes added are too high

Question 4

Explain why deionised water used for rinsing has no effect on the accuracy of the titre

Answer 4

This does not change the number of moles of reagents / water is not a reagent / water is one of the products

Question 5

Suggest one reason why repeating a titration makes the value of the average titre more reliable

Answer 5

Idea that a single titration could be flawed / anomalous

Allow ‘to obtain concordant results’.

Question 7

Why use a Burette

Answer 7

Sensitive.. scale gos up in 0.1cm3 intervals
Measure continuous data

Question 8

What is the equation for uncertainty

Answer 8

Percentage uncertainty= (uncertainty/ reading) x100
For multiple readings

(uncertainty’s X number of readings )/ change in readings x100