Question

(a) When a compound containing C, H, and O is completely combusted in air, what reactant besides the hydrocarbon is involved in the reaction? (b) What products form in this reaction? (c) What is the sum of the coefficients in the balanced chemical equation for the combustion of one mole of acetone, \(\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}(l),\) in air?

Short answer

(a) The other reactant involved in the combustion reaction is oxygen gas, O2. (b) The products formed in the reaction are carbon dioxide (CO2) and water (H2O). (c) The sum of the coefficients in the balanced chemical equation for the combustion of one mole of acetone is 11. The balanced equation is: \( C_{3}H_{6}O(l) + 4O_{2}(g) \rightarrow 3CO_{2}(g) + 3H_{2}O(l) \).

Step-by-step solution

(a) Identifying the other reactant in the combustion reaction

In a combustion reaction, when a compound containing C, H, and O is combusted, the other reactant is oxygen gas, O2.

(b) Identifying the products in the combustion reaction

In a complete combustion reaction involving a hydrocarbon (compound containing only C and H) or a compound containing C, H, and O, the products formed are carbon dioxide (CO2) and water (H2O).

(c) Balancing the equation for the combustion of one mole of acetone

To balance the equation for the combustion of one mole of acetone (C3H6O), we need to balance the number of atoms of each element on both sides of the reaction. The unbalanced equation is: C3H6O(l) + O2(g) → CO2(g) + H2O(l) 1. Balance the Carbon atoms: C3H6O(l) + O2(g) → 3CO2(g) + H2O(l) 2. Balance the Hydrogen atoms: C3H6O(l) + O2(g) → 3CO2(g) + 3H2O(l) 3. Balance the Oxygen atoms: C3H6O(l) + 4O2(g) → 3CO2(g) + 3H2O(l) Now, the balanced chemical equation for the combustion of one mole of acetone is: C3H6O(l) + 4O2(g) → 3CO2(g) + 3H2O(l)

Calculate the sum of the coefficients in the balanced equation

The balanced chemical equation is C3H6O(l) + 4O2(g) → 3CO2(g) + 3H2O(l). Therefore, the sum of the coefficients in this balanced equation is 1 (acetone) + 4 (oxygen) + 3 (carbon dioxide) + 3 (water) = 11.

Key concepts

chemical equation balancing

Balancing a chemical equation is like solving a puzzle. The goal is to have the same number of each type of atom on both sides of the equation. This ensures the law of conservation of mass is satisfied, meaning that mass is neither created nor destroyed in a chemical reaction. For example, in the combustion of acetone, represented by the chemical formula \( \text{C}_3\text{H}_6\text{O} \), we start with an unbalanced equation:
\[ \text{C}_3\text{H}_6\text{O}(l) + \text{O}_2(g) \rightarrow \text{CO}_2(g) + \text{H}_2\text{O}(l) \]
To balance it:

• Start with carbon: Acetone has 3 carbon atoms, so we need 3 \( \text{CO}_2 \) molecules.
• Next, balance hydrogen: There are 6 hydrogen atoms in acetone, requiring 3 \( \text{H}_2\text{O} \) molecules.
• Finally, balance oxygen: Check the number of oxygen atoms needed, which ends up requiring 4 \( \text{O}_2 \) molecules.

Thus, the balanced equation for the combustion of acetone is:\[\text{C}_3\text{H}_6\text{O}(l) + 4\text{O}_2(g) \rightarrow 3\text{CO}_2(g) + 3\text{H}_2\text{O}(l)\]

acetone combustion

Acetone, commonly known as nail polish remover, undergoes combustion, a process that involves burning in the presence of oxygen. This reaction is an example of a chemical reaction where energy is released, usually in the form of heat and light. Combustion of organic compounds like acetone, which contain carbon, hydrogen, and oxygen, typically results in the formation of carbon dioxide and water.
In practical terms, acetone combusts according to the equation:
\[\text{C}_3\text{H}_6\text{O}(l) + 4\text{O}_2(g) \rightarrow 3\text{CO}_2(g) + 3\text{H}_2\text{O}(l)\]
This reaction illustrates complete combustion, meaning acetone is fully converted into \( \text{CO}_2 \) and \( \text{H}_2\text{O} \) without any leftover acetone. It's important to have enough oxygen to ensure complete combustion, preventing the formation of carbon monoxide or other byproducts.

oxygen as reactant

Oxygen is a critical reactant in combustion reactions. It pairs with hydrocarbons, substances made of hydrogen and carbon, or compounds containing carbon, hydrogen, and oxygen to sustain the reaction. Without sufficient oxygen, combustion cannot occur. This is why oxygen is always involved in burning processes, such as the combustion of acetone.
In the combustion of acetone, \( \text{O}_2 \) molecules are needed to break the bonds in the acetone molecule and rearrange its atoms to form new compounds:

• The chemical equation shows that 4 molecules of \( \text{O}_2 \) are necessary to react with 1 molecule of acetone.
• The presence of oxygen ensures carbon is converted into carbon dioxide and hydrogen into water, completing the reaction.

Without enough oxygen, incomplete combustion might occur, leading to lower energy output and the potential production of harmful substances like carbon monoxide.

combustion products

The combustion products of any hydrocarbon or oxygen-containing hydrocarbon like acetone are primarily carbon dioxide and water. These products result from the chemical transformation that occurs during combustion. Each carbon atom in the fuel combines with oxygen to form \( \text{CO}_2 \), while each pair of hydrogen atoms combines with oxygen to form \( \text{H}_2\text{O} \).
In the case of acetone, the balanced chemical reaction tells us:

• 3 molecules of \( \text{CO}_2 \) are produced from the 3 carbon atoms in acetone.
• 3 molecules of \( \text{H}_2\text{O} \) result from the 6 hydrogen atoms.

This conversion is efficient and maximizes energy release, which is why \( \text{CO}_2 \) and \( \text{H}_2\text{O} \) are the hallmark products of any complete combustion process.