Chemical Equation Chemistry Example 4

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Example 4

hard
A student writes the following unbalanced equation for the reaction of aluminum with sulfuric acid: Al+H2SO4→Al2(SO4)3+H2\text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2. Balance this equation and verify by counting all atoms on each side.

Solution

  1. 1
    Balance Al: 2 on right, so put 2 on left: 2Al2\text{Al}. Balance SO4\text{SO}_4: 3 on right, so put 3 on left: 3H2SO43\text{H}_2\text{SO}_4.
  2. 2
    Check H: left has 3×2=63 \times 2 = 6 H atoms, so need 3H23\text{H}_2 on right (gives 6 H). Balanced equation: 2Al+3H2SO4→Al2(SO4)3+3H22\text{Al} + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{H}_2.
  3. 3
    Verify: Al 2=2, H 6=6, S 3=3, O 12=12. All balanced.

Answer

2Al+3H2SO4→Al2(SO4)3+3H22\text{Al} + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{H}_2
Polyatomic ions like sulfate (SO42−\text{SO}_4^{2-}) can be balanced as a group when they appear unchanged on both sides of the equation, simplifying the balancing process.

About Chemical Equation

A written representation of a chemical reaction using chemical formulas for reactants and products, coefficients to indicate mole ratios, state symbols to show physical states.

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