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Which of the following is the correctly balanced equation for the reaction of magnesium with oxygen to form magnesium oxide?

easy MCQ 1 mark Class 10 · Science · Chemical Reactions and Equations
  1. 2Mg + O2 → 2MgO
  2. Mg + O2 → MgO2
  3. Mg + O → MgO
  4. 2Mg + O → Mg2O
Answer
2Mg + O2 → 2MgO

The correct answer is 2Mg + O2 → 2MgO — Verify that both sides have 2 Mg atoms and 2 O atoms; the equation is balanced.

Step-by-step solution

  1. Write the unbalanced equation: .
  2. Count the atoms on both sides: left has 1 Mg and 2 O; right has 1 Mg and 1 O.
  3. Balance oxygen by placing coefficient 2 before MgO: , which now gives 2 Mg on the right.
  4. Balance magnesium by placing coefficient 2 before Mg on the left: .
  5. Verify that both sides have 2 Mg atoms and 2 O atoms; the equation is balanced.
Common mistake: Balancing O2 by changing O instead of using whole molecules

Concept tested: Balancing chemical equations

Published · How this solution was prepared and checked

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