Multiple Choice
Which of the following is the correctly balanced chemical equation for the reaction between hydrogen gas and oxygen gas to form water?
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3. Chemical Reactions
Balancing Chemical Equations
Multiple Choice
Which of the following is the correctly balanced equation for the combustion of methane, and what type of reaction is it?
A
CH_4 + 2 O_2 → CO + 2 H_2O; decomposition reaction
B
CH_4 + 2 O_2 → CO_2 + 2 H_2O; combustion reaction
C
CH_4 + O_2 → C + 2 H_2O; single replacement reaction
D
CH_4 + O_2 → CO_2 + H_2O; synthesis reaction
Verified step by step guidance1
Identify the reactants and products in the combustion of methane. Methane (CH_4) reacts with oxygen (O_2) to produce carbon dioxide (CO_2) and water (H_2O).
Write the unbalanced chemical equation for the combustion of methane: \(\mathrm{CH_4 + O_2 \rightarrow CO_2 + H_2O}\).
Balance the carbon atoms first. There is 1 carbon atom in CH_4 and 1 in CO_2, so carbon is balanced.
Balance the hydrogen atoms next. There are 4 hydrogen atoms in CH_4 and 2 in each H_2O molecule, so place a coefficient of 2 before H_2O: \(\mathrm{CH_4 + O_2 \rightarrow CO_2 + 2 H_2O}\).
Balance the oxygen atoms last. On the right side, there are 2 oxygen atoms in CO_2 and 2 × 1 = 2 oxygen atoms in 2 H_2O, totaling 4 oxygen atoms. Since O_2 is diatomic, place a coefficient of 2 before O_2: \(\mathrm{CH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O}\).
Recognize that this reaction is a combustion reaction because it involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water.
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