Practicals

Question 1

In a titration, 0.002 mol dm^-3 potassium manganate is used rather than 0.02. Why?

Answer 1

Larger titre leading to less percentage error.

Question 2

What affects how big the uncertainty is?

Answer 2

The measuring instrument - what increments does it go up in?
Uncertainty with the procedure (repeat to limit this)
Making a judgement.

Question 3

How do you calculate the uncertainty of repeated measurements?

Question 4

How do you calculate percentage uncertainty?

Answer 4

Uncertainty/ measurement x 100

Question 5

How do you reduce percentage uncertainty?

Answer 5

More sensitive equipment or increase the measurement.

Question 6

Suggest ways a student could improve the quality of her scientific drawing.

Answer 6

No shading. Only use single lines. Add further labels. Don’t allow label lines to intersect. Add magnification.

Question 7

How do you find percentage yield when you are given the moles of reactant?

Answer 7

Use moles of reactants to find moles of product. Use actual moles of product / expected moles of product.

Question 8

Explain why an air bubble increases the final burette reading.

Answer 8

Air bubble takes up volume that would be filled by acid.