C2 Calculations and analysis

Question 1

In the column, what can be used to help identify the substance?

Answer 1

The retention time

Question 2

A sample of calcium compound contains 0.8g of calcium, 0.64g of oxygen and 0.04g of hydrogen, find its empirical formula.

Answer 2

Mass ÷ Mr

Ca – 0.8 O – 0.64 H – 0.04

40 = 0.02 16 = 0.04 1 = 0.04

Divide by the smallest

Ca – 0.02 O – 0.04 H – 0.04

0.02 = 1 0.02 = 2 0.02 = 2

= CaO₂H₂

Question 3

What is shown by the molecular ion peak?

Answer 3

Relative formula mass of substance

Question 4

What method can be used to analysis food additives?

Answer 4

Paper Chromatography

Question 5

What is separated in gas chromatography?

Answer 5

Mixture of compounds

Question 6

What can a mass spectrometer be used for?

Answer 6

Gives the relative formula mass

Question 7

What is the percentage yield if a reaction only produces 20g when in theory it produces 40g.

Answer 7

% yield = (20 ÷ 40) x 100 = 50%

Question 8

Give 3 reasons why the yield is not 100%.

Answer 8

Reversible reaction

Product can be lost when separated

Other reactions occur