During the complete combustion of one molecule of methane (CH_4), how many covalent bonds are broken in the reactant molecules before new bonds are formed in the products?

• A. 4 bonds
• B. 2 bonds
• C. 5 bonds
• D. 6 bonds

Answer: (C)

Verified step by step guidance

1. Write the balanced chemical equation for the complete combustion of methane: \(\mathrm{CH_4 + 2\ O_2 \rightarrow CO_2 + 2\ H_2O}\).
2. Identify all the covalent bonds present in the reactant molecules. In methane (\(\mathrm{CH_4}\)), there are 4 C-H bonds. In oxygen (\(\mathrm{O_2}\)), each molecule has 1 O=O double bond, and since there are 2 \(\mathrm{O_2}\) molecules, there are 2 O=O bonds total.
3. Count the total number of bonds broken in the reactants. This includes breaking all 4 C-H bonds in methane and both O=O double bonds in the two oxygen molecules, so total bonds broken = 4 (C-H) + 2 (O=O) = 6 bonds.
4. Note that the question asks specifically for the number of bonds broken before new bonds form, so focus only on the bonds in the reactants that must be broken to allow the reaction to proceed.
5. Summarize that the total number of covalent bonds broken in the reactants during the complete combustion of one methane molecule is 6.