Page 1: Fundamental Quantitative Chemistry Concepts
The page covers essential concepts in quantitative chemistry, including relative formula mass calculations, moles, conservation of mass, and limiting reactants. These concepts are crucial for solving quantitative chemistry gcse questions.
Definition: Relative Formula Mass (Mr) is calculated by adding together the relative atomic masses (Ar) of all atoms in a compound's molecular formula.
Example: For magnesium chloride (MgCl₂), Mr = 24 + (35.5 × 2) = 95
Vocabulary: A mole is a unit measuring the amount of chemical substance, containing 6.02 × 10²³ particles (Avogadro's constant).
Highlight: Conservation of mass states that no atoms are created or destroyed during chemical reactions, only bonds change.
The page elaborates on limiting reactants, explaining how they affect product formation:
Definition: A limiting reactant is the substance that controls the maximum amount of product that can be formed in a reaction.
A detailed example demonstrates mass calculations:
- Write the balanced equation
- Calculate moles of known substance
- Determine moles of unknown substance using molar ratios
- Calculate final mass of unknown substance
Example: When calculating sodium oxide production from 5.0g sodium:
- Balanced equation: 4Na + O₂ → 2Na₂O
- Moles of Na = 5 ÷ 23 = 0.217
- Moles of Na₂O = 0.217 ÷ 2 = 0.1085
- Mass of Na₂O = 0.1085 × 62 = 6.13g
The page also covers percentage mass calculations:
Formula: Percentage mass = (Ar × number of atoms × 100) ÷ Mr of compound
