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Balancing equations – practice for Years 8–9

Sample questions on Balancing equations with the right answer and a worked solution, from easy to hard. In the Pickles Academy app a child gets new questions of the same kind every time, so they can't just learn the answers by heart.

Subject
Chemistry
Year
Years 8–9
Curriculum area
Chemical reactions

Question types: Balance the equation

Rule: Balancing equations

Atoms are not made or destroyed in a reaction: there must be the same number of each kind on both sides.

Only add numbers in front of formulas; never change the small numbers inside them.

Example: Ca + 2 H₂O → Ca(OH)₂ + H₂: on each side 1 Ca, 4 H, 2 O

Watch out: The big number multiplies the whole formula: 2 H₂O means 4 hydrogen atoms and 2 oxygen atoms.

Sample questions

  1. Question 1 Easy

    Fill in the missing coefficient (?) so that the equation is balanced: ? Ca + O₂ → 2 CaO

    Show the solution
    Answer: 2

    How it works: 2 Ca + O₂ → 2 CaO. In front of Ca: 2.

  2. Question 2 Normal

    Fill in the missing coefficient (?) so that the equation is balanced: Mg + ? HCl → MgCl₂ + H₂

    Show the solution
    Answer: 2

    How it works: Mg + 2 HCl → MgCl₂ + H₂. In front of HCl: 2.

  3. Question 3 Hard

    Balance the equation with the smallest whole numbers: NaOH + H₂SO₄ → Na₂SO₄ + H₂O. What is the sum of all the coefficients (count a 1 too)?

    Show the solution
    Answer: 6

    How it works: 2 NaOH + H₂SO₄ → Na₂SO₄ + 2 H₂O; 2 + 1 + 1 + 2 = 6.

Related topics

All Chemistry topics

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