Chemical Reactions and Equations

Practice past-paper questions

Practise O/L exam questions on Chemical Reactions and Equations with worked solutions

1. 2022 · Paper II · 5 marks
   Magnesium ribbon burns in oxygen to form magnesium oxide. (i) Write the balanced chemical equation for this reaction. (ii) Classify this as a combination, decomposition, displacement or double-displacement reaction. (iii) Name TWO signs that indicate a chemical reaction has occurred in this experiment.
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   (i) 2Mg + O₂ → 2MgO (ii) Combination (synthesis) reaction — two substances combine to form one product. (iii) Bright white light / flame produced; white ash (MgO) forms (any two of: light, heat, new substance formed, colour change accepted).
   Source: NIE O/L Science 2022 Paper II Q4

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