Atomic structure, analysis and quantitive chemistry

Question 1

Explain why the mass number of oxygen is 16.

You should refer to the numbers of sub-atomic particles in the nucleus of the atom. [2]

Answer 1

there are 8 protons and 8 neutrons (in the nucleus)

Question 2

Explain why carbon-12 and carbon-14 are isotopes of carbon.

You should refer to the numbers of sub-atomic particles in the nucleus of each isotope. [3]

Answer 2

• both atoms have the same number of protons
• carbon-12 has 6 neutrons
• carbon-14 has 8 neutrons

Question 3

One mole of a substance is the relative formula mass in ______.
The relative atomic mass of an element compares the mass of an atom of an element with the mass of an atom ______. [2]

Answer 3

• grams

- carbon-12

Question 4

Metal oxides react with acids to make salts.

What type of compound is a metal oxide? [1]

Answer 4

base

Question 5

State how solid lead nitrate can be obtained from lead nitrate solution. [1]

Answer 5

by evaporation / crystallisation

Question 6

Why do different compounds separate in a gas chromatography column? [1]

Answer 6

different substances travel at different speeds

Question 7

Give one reason why the calculated yield of magnesium might not be obtained. [1]

Answer 7

• the reaction is reversible
• some get lost / released
• some of the reactant may react in different ways

Question 8

What is the purpose of gas chromatography? [1]

Answer 8

to separate

Question 9

What information do the molecular ion peaks from the mass spectrometer give about the substances? [1]

Answer 9

(relative) molecular mass