Multiple Choice
Which of the following lists the reactants in the chemical equation: 3Mg(s) + 2FeCl_3(aq) → 2Fe(s) + 3MgCl_2(aq)?
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3. Chemical Reactions
Balancing Chemical Equations
Multiple Choice
Which of the following is the correctly balanced chemical equation for the combustion of glucose (C6H12O6)?
A
C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O
B
C6H12O6 + 6 O2 -> 12 CO2 + 6 H2O
C
C6H12O6 + 12 O2 -> 6 CO2 + 12 H2O
D
C6H12O6 + 6 O2 -> 6 CO + 6 H2O
Verified step by step guidance1
Write the unbalanced chemical equation for the combustion of glucose: \(\mathrm{C_6H_{12}O_6 + O_2 \rightarrow CO_2 + H_2O}\).
Balance the carbon atoms first. Since glucose has 6 carbon atoms, place a coefficient of 6 in front of \(\mathrm{CO_2}\): \(\mathrm{C_6H_{12}O_6 + O_2 \rightarrow 6 CO_2 + H_2O}\).
Balance the hydrogen atoms next. Glucose has 12 hydrogen atoms, so place a coefficient of 6 in front of \(\mathrm{H_2O}\) (because each water molecule has 2 hydrogens): \(\mathrm{C_6H_{12}O_6 + O_2 \rightarrow 6 CO_2 + 6 H_2O}\).
Balance the oxygen atoms last. On the right side, there are \(6 \times 2 = 12\) oxygens from \(\mathrm{CO_2}\) and \(6 \times 1 = 6\) oxygens from \(\mathrm{H_2O}\), totaling 18 oxygen atoms. On the left, glucose provides 6 oxygens, so the remaining oxygen atoms must come from \(\mathrm{O_2}\). Set up the equation: \$6 + 2x = 18\(, where \)x$ is the coefficient for \(\mathrm{O_2}\).
Solve for \(x\) to find the coefficient for \(\mathrm{O_2}\), which balances the oxygen atoms. This will give the balanced equation: \(\mathrm{C_6H_{12}O_6 + 6 O_2 \rightarrow 6 CO_2 + 6 H_2O}\).
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