WJEC A Level Chemistry
WJEC A Level Chemistry 1.3 Chemical Calculations Exam Questions
Free WJEC A Level Chemistry exam questions on 1.3 Chemical Calculations, with mark schemes. Covers relative masses, moles, empirical formulae, gas volumes, concentrations, yield and atom economy.
1.3 Chemical Calculations exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
StemUp mark scheme flashcards
WJEC A Level Chemistry Flashcards (Anki & Quizlet)
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Use them on Anki or Quizlet, then test yourself with the questions on this page.
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About WJEC A Level Chemistry 1.3 Chemical Calculations
This topic covers the core quantitative chemistry. Titration and mole calculations appear on every paper.
What you need to know
- The mole n = m / M, Avogadro's constant and molar gas volume.
- Concentration n = c x V, with volumes in dm³.
- Formulae Empirical and molecular formulae from mass or percentage data.
- Efficiency Percentage yield and atom economy; errors and significant figures in practical work.
Common mistakes in 1.3 Chemical Calculations
- Forgetting to convert cm³ to dm³.
- Rounding too early in multi-step calculations.
- Confusing percentage yield with atom economy.
Try three 1.3 Chemical Calculations exam-style questions
1. Calculate the moles in 25.0 cm³ of 0.100 mol dm⁻³ HCl. (1 mark)
Show the mark scheme answer
0.0250 x 0.100 = 2.50 x 10⁻³ mol.
2. A compound is 40.0% C, 6.7% H and 53.3% O by mass. Find its empirical formula. (2 marks)
Show the mark scheme answer
Moles: C 3.33, H 6.7, O 3.33 (1); ratio 1:2:1 so CH₂O (1).
3. Define atom economy. (1 mark)
Show the mark scheme answer
The mass of the desired product divided by the total mass of products, x 100.
1.3 Chemical Calculations FAQs
What does Chemical Calculations cover?
Moles, concentrations, gas volumes, formulae, yield and atom economy.
Which practicals link here?
Acid-base titrations and determining the formula of a compound.
How many significant figures should I use?
Match the least precise data given, usually 3.
Revise this topic with flashcards: WJEC A Level Chemistry Flashcards, with mark scheme answers for Anki and Quizlet.
