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Reviewed CSCA Chemistry question · Standard

Which of the following equations is correctly balanced for the reaction between solid aluminum carbide (Al4C3) and water to produce solid aluminum hydroxide and methane gas?

  1. Al4C3(s) + 12H2O(l) → 4Al(OH)3(s) + 3CH4(g)
  2. Al4C3(s) + 6H2O(l) → 2Al(OH)3(s) + 3CH4(g)
  3. Al4C3(s) + 10H2O(l) → 4Al(OH)3(s) + 3CH4(g)
  4. Al4C3(s) + 12H2O(l) → 4Al(OH)3(s) + 2CH4(g)
Show the answer and explanation

Correct answer

A. Al4C3(s) + 12H2O(l) → 4Al(OH)3(s) + 3CH4(g)

Principle or equation

A balanced chemical equation must have the same number of each type of atom on both sides. For Al4C3 + H2O → Al(OH)3 + CH4, balance Al, C, H, and O.

Why this answer is correct

Start with Al: 4 Al on left, so 4 Al(OH)3 on right. C: 3 C on left, so 3 CH4 on right. Now count H: right has 4×3 + 3×4 = 12 + 12 = 24 H. Left must have 24 H, so 12 H2O. Check O: left 12 O, right 4×3 = 12 O. Balanced.

Example

For Al4C3 + 12H2O → 4Al(OH)3 + 3CH4, atoms: Al 4=4, C 3=3, H 24=24, O 12=12.

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