1.7 Quantitative Chemistry
Relative formula mass, percentage composition, moles, reacting masses, empirical formula, limiting reactants and percentage yield.
How to study for CCEA GCSE Chemistry
Connect particle models to observations, balance every quantitative relationship, and prepare each prescribed practical from safe method through analysis and evaluation.
Core concepts
Concept 1
The mole connects particle-scale formulae to measurable masses using relative formula mass.
Exam cue: Convert the given mass to moles before applying the equation ratio.
Concept 2
Balanced-equation coefficients give mole ratios, not direct mass ratios.
Exam cue: For empirical formula, divide each mass or percentage by relative atomic mass, then simplify.
Concept 3
Empirical formula and yield calculations require explicit conversion, simplest ratios and comparison of actual with theoretical outcomes.
Exam cue: State whether a result is theoretical, actual or a percentage of the theoretical amount.
Risk pitfalls and guardrails
Using grams directly in a mole ratio.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Rounding an intermediate ratio too early and losing a simple whole-number relationship.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Dividing theoretical yield by actual yield instead of actual by theoretical.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a particle-level explanation with a vague observation.
Memory anchors
Mole from mass
Amount in moles equals mass divided by relative formula mass.
Reacting ratio
Use coefficients from the balanced equation as the mole ratio.
Empirical formula
The simplest whole-number ratio of atoms in a compound.
Limiting reactant
The reactant consumed first, fixing the maximum product amount.
Percentage yield
Actual yield divided by theoretical yield, multiplied by 100.
Percentage by mass
Element mass contribution divided by formula mass, multiplied by 100.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is the amount in 18 g of water, Mr=18?
What mass is 0.50 mol of CO₂, Mr=44?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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