Question

propane burns in oxygen to produce carbon dioxide and water. what are the chemical formulas of the reactants and products?
the formulas of the reactants are $\ce{c_{3}h_{8}}$, $\ce{o}$, and $\ce{co_{2}}$. the formula of the product is $\ce{h_{2}o}$.
the formulas of the reactants are $\ce{c_{3}h_{8}}$ and $\ce{o_{2}}$. the formulas of the products are $\ce{co}$ and $\ce{h_{2}o}$.
the formulas of the reactants are $\ce{c_{3}h_{8}}$ and $\ce{o_{2}}$. the formulas of the products are $\ce{co_{2}}$ and $\ce{h_{2}o}$.

Explanation:

1. Reactants are the substances that undergo a chemical reaction. In the combustion of propane, propane ($\ce{C_3H_8}$) and oxygen ($\ce{O_2}$) are the reactants because they are the starting materials.
2. Products are the substances formed. Complete combustion of hydrocarbons (like propane) in oxygen produces carbon dioxide ($\ce{CO_2}$) and water ($\ce{H_2O}$).

• First option is wrong as $\ce{CO_2}$ is a product, not a reactant, and it lists only one product incorrectly.
• Second option is wrong as incomplete combustion would produce $\ce{CO}$, but the problem states propane burns to produce $\ce{CO_2}$ and $\ce{H_2O}$, indicating complete combustion.
• Third option correctly identifies reactants as $\ce{C_3H_8}$ (propane) and $\ce{O_2}$ (oxygen), and products as $\ce{CO_2}$ (carbon dioxide) and $\ce{H_2O}$ (water).

Answer:

The formulas of the reactants are $\ce{C_3H_8}$ and $\ce{O_2}$. The formulas of the products are $\ce{CO_2}$ and $\ce{H_2O}$. (The third option in the given choices)