Final answer:
The equation is not balanced as it stands. The correct balanced chemical equation for the combustion of methane is CH4 + 2O2 → CO2 + 2H2O, which has an equal number of atoms for each element on both sides of the equation.
Step-by-step explanation:
The student's equation 2CH4 + 4O2 -> CO2 + 4H2O is not balanced because the numbers of carbon, hydrogen, and oxygen atoms on both sides of the reaction do not match. Taking CH4 + 2O2 → CO2 + 2H2O as a reference for balancing, we should have equal numbers of atoms for each element on both sides. A balanced equation ensures the law of conservation of mass is upheld.
Upon inspection of the original equation, we observe that there are two carbon atoms in the form of CH4 on the reactant side but only one carbon atom in CO2 on the product side. Oxygen is balanced, with four O2 molecules as reactants and a total of four oxygen atoms within the two water molecules and two oxygen atoms within the CO2 product. Lastly, hydrogen is unbalanced with eight hydrogen atoms as part of 2CH4 but only four within 4H2O on the product side.
To balance the equation, we need an equal amount of carbon and hydrogen on both sides. The correct balanced chemical equation for the combustion of methane should be: CH4 + 2O2 → CO2 + 2H2O.