AQA Chemistry GCSE (Topic 3: Quantitative Chemistry)

Question 1

What is the law of conservation of mass?

Answer 1

The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.

Question 2

Write a balanced equation of magnesium reacting with hydrochloric acid.

Answer 2

Mg (s) + 2 HCI (aq) - MgCI 2(aq) + H 2(g)

Question 3

Define relative atomic mass and the relative formula mass.

Answer 3

RAM - average mass of atoms in an element taking into account masses and abundance of its isotopes, relative to 12^C.
RFM - sum of RAM’s of all atoms in the formula.

Question 4

Write down the two formulae that link concentration, mass and volume together.

Answer 4

Concentration (g per dm^3) = Mass (g)/Volume (dm^3)
Concentration (mol per dm^3) = nr of moles/volume (dm^3)

Question 5

What is the molar volume of a gas at room temperature and pressure?

Answer 5

1 mole of a gas at room temperature and pressure occupies 24 dm^3

Question 6

What is titration?

Answer 6

A technique for finding the concentration of a solution by reacting a known volume of this solution with a solution of known concentration.

Question 7

Why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

Answer 7

The reaction may not go to completion because it is reversible.
Some of the product may be lost when it is seperated from the reaction mixture.
Some of the reactants may react in ways different to the expected reaction (side reactions may occur)