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Reviewed CSCA Chemistry question · Standard

Which of the following equations is correctly balanced for the reaction between zinc sulfide and oxygen gas to produce zinc oxide and sulfur dioxide?

  1. ZnS + O2 → ZnO + SO2
  2. 2ZnS + 3O2 → 2ZnO + 2SO2
  3. 2ZnS + 2O2 → 2ZnO + SO2
  4. ZnS + 2O2 → ZnO + SO2
Show the answer and explanation

Correct answer

B. 2ZnS + 3O2 → 2ZnO + 2SO2

Principle or equation

A balanced chemical equation has equal numbers of each type of atom on both sides.

Why this answer is correct

For ZnS + O2 → ZnO + SO2, balancing Zn gives 1 on both sides. For S, 1 on both sides. For O, left has 2, right has 3 (1 in ZnO + 2 in SO2). Multiply all by 2: 2ZnS + 3O2 → 2ZnO + 2SO2. Now O: left 6, right 2+4=6. Balanced.

Example

Balancing CH4 + O2 → CO2 + H2O gives CH4 + 2O2 → CO2 + 2H2O.

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