C2 - Mass, Moles & Analysis

Question 0

What is the mass number of an atom?

Answer 0

The number of protons and neutrons in the nucleus.

Question 1

What is the atomic number of an atom?

Answer 1

The number of protons an atom has.

Question 2

What are isotopes?

Answer 2

Atoms with different numbers of neutrons.

Question 3

What is the relative mass of a proton and neutron?

Answer 3

1

Question 4

What is the relative mass of an electron?

Answer 4

1/1836

Question 5

What is the relative formula mass of a compound?

Answer 5

The sum of the relative atomic mass of all of the atoms.

Question 6

What is the mass of a mole of carbon, oxygen and iron?

Answer 6

• 12g
• 16g
• 56g

Question 7

How is the percentage mass of an element in a compound found?

Answer 7

(mass of element / total mass of compound) x 100

Question 8

How is the empirical formula found?

Answer 8

Simplest ratio of moles.

Question 9

How is the number of moles of an element in a compound found?

Answer 9

mass of the element / relative atomic mass

Question 10

What is the yield of a chemical reaction?

Answer 10

How much product was made.

Question 11

How is percentage yield calculated?

Answer 11

(amount produced / maximum amount possible) x 100

Question 12

Give five reasons why yield is rarely 100%.

Answer 12

• The reaction may be reversible.
• Some reactants may give unexpected products.
• The product may be lost in the apparatus.
• The reactants may not be completely pure.
• It may be difficult to separate products.

Question 13

Why is it important to maximise yield?

Answer 13

• In order to produce less waste.
• Reduce energy usage.
• Conserve limited resources.
• Reduces pollution.

Question 14

What is a reversible reaction?

Answer 14

The products of the reaction can react to make the original reactants.

Question 15

How are reversible reactions represented?

Answer 15

With the ⇌ symbol.

Question 16

What are E numbers?

Answer 16

European food additive code.

Question 17

How does paper chromatography work?

Answer 17

Some compounds in a mixture dissolve better than others in particular solvents.

Question 18

Give three advantages of using instrumental analysis.

Answer 18

• They are highly accurate and sensitive.
• They are quicker.
• They enable very small samples to be analysed.

Question 19

Give three disadvantages of instrumental analysis.

Answer 19

• It is usually very expensive.
• It takes special training to use.
• It gives results that can only be interpreted by comparison with known substance data.

Question 20

What is gas spectrometry?

Answer 20

Separating compounds that are easily vaporised.

Question 21

What is the mass spectrometer?

Answer 21

The instrument that identifies compounds.

Question 22

Explain gas chromatography.

Answer 22

• The sample mixture is vaporised.
• A carrier gas moves the vapour through the coiled column.
• The compounds have different attractions to the material in the column. The compounds that have the stronger attractions have a longer retention time.

Question 23

What is the molecular ion peak?

Answer 23

The peak with the largest mass which is shown at the end.