C3 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 if magnesium reacting with hydrochloric acid

Answer 2

Mg(s) + 2HCl(aq) ——> MgCl2(aq) + H2(g)

Question 3

Define relative atomic mass and relative formula mass

Answer 3

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

Question 4

The following reaction occurs in a test tube under a Bunsen burner:
4MgO(s) + CH4(g) —> 4Mg(s) + 2H2O(g) + CO2(g)
The carbon dioxide and water escape from the test tube
Use the equation to explain why

Answer 4

The are both gases

Question 5

What is avogadros constant?

Answer 5

The number of atoms, molecules or ions in a mole of a given substance. The value of the constants is 6.02x10^23

Question 6

What is the formula that links mass, molecular mass and moles together

Answer 6

Mass = Mr x moles

Question 7

State what is meant by a limiting reactant in a chemical reaction

Answer 7

In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactants is used. The reactant that is completely used up is called the limiting reactant because it limits the amount of products

Question 8

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

Answer 8

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