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Difficulty: MediumChemical Reactions and Compounds

Complete the following statement regarding the complete combustion of methane fuel by identifying the missing compound and the stoichiometric balancing coefficient.

Answer:During the complete combustion of methane (CH4CH_4), the fuel reacts with atmospheric oxygen (O2O_2) to produce carbon dioxide (CO2CO_2) and 【water】. In the balanced chemical equation CH4+‾O2→CO2+2H2OCH_4 + \underline{\quad} O_2 \rightarrow CO_2 + 2H_2O, the numerical coefficient required in front of O2O_2 is 【2】.

Answer

The missing product compound is water (H2OH_2O), and the balancing coefficient for oxygen gas (O2O_2) is 2.
In the complete combustion of any simple hydrocarbon such as methane (CH4CH_4), the products are always carbon dioxide (CO2CO_2) and water (H2OH_2O). To balance the equation CH4+xO2→CO2+2H2OCH_4 + x O_2 \rightarrow CO_2 + 2H_2O, we tally the atoms on each side. Carbon has 1 atom on both sides; hydrogen has 4 atoms on both sides (44 in CH4CH_4 and 2×2=42 \times 2 = 4 in 2H2O2H_2O). The product side contains 4 total oxygen atoms (2 from CO2CO_2 and 2 from 2H2O2H_2O). Therefore, 22 molecules of diatomic oxygen (2O22 O_2) are required on the reactant side to conserve mass.

Step-by-Step Solution

1
Identify the missing chemical product containing hydrogen.
Water (H2OH_2O)
Hydrocarbon combustion involves the oxidation of carbon to carbon dioxide (CO2CO_2) and hydrogen to water (H2OH_2O).
2
Count total oxygen atoms present in the products.
4 oxygen atoms total
The products consist of 1 molecule of CO2CO_2 (contributing 2 oxygen atoms) and 2 molecules of H2OH_2O (contributing 2×1=22 \times 1 = 2 oxygen atoms), giving 2+2=42 + 2 = 4 oxygen atoms.
3
Determine the required coefficient for diatomic oxygen (O2O_2) on the reactant side to satisfy the law of conservation of mass.
A coefficient of 2
Since each O2O_2 molecule contains 2 oxygen atoms, dividing 4 required oxygen atoms by 2 yields a stoichiometric coefficient of 2.

Key Concept

Hydrocarbon Combustion and Equation Balancing
Estimated Time:1m 0s
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Topics

Chemical Reactions and Compounds

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