Paper 5 MS

Question 1

Describe how the student could check that the mass of KI transferred into the 100cm3 beaker was exactly the same as the mass calculated

Answer 1

(Re)weigh the empty weighing boat

and the difference should be the calculated mass

Question 2

Describe how the student should transfer all the KI solution from the beaker into the 250cm3 volumetric flask

Answer 2

(pour using a funnel and) rinse the beaker with (distilled) water

Question 3

Describe how the student should fill the volumetric flask exactly up to the 250cm3 mark.

Answer 3

add (distilled) water dropwise near the mark

Question 4

The student rinsed a burette with solution A before filling it with solution A.
Explain why this improves the accuracy of the results.

Answer 4

the solution in the burette is at the expected concentration.
prevention of dilution (by residual distilled water) of the solution in the apparatus.

Question 5

Suggest why the results shown in the table could be considered reliable.

Answer 5

the recorded times are repeatable / the recorded times can be duplicated / the repeated times are close to one another

Question 6

Suggest why a measuring cylinder was used to measure the volume of H2SO4(aq) rather than a more accurate piece of apparatus, such as a burette.

Answer 6

acid is in excess