Problem 18 - Chemistry The Central Science

Question

(a) When a compound containing \(\mathrm{C}, \mathrm{H},\) and \(\mathrm{O}\) 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?

Step-by-Step Solution

Answer

(a) The reactant besides the hydrocarbon involved in the combustion process is oxygen (O2). (b) The products formed during the combustion process 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, C3H6O, in air is 10.5.

Step 1: a) Identifying the reactant

In a complete combustion reaction, the hydrocarbon reacts with oxygen (O2) from the air. Therefore, the reactant besides the hydrocarbon involved in the reaction is oxygen (O2).

Step 2: b) Identifying the products

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

Step 3: c) Balancing the chemical equation and finding the sum of coefficients

To find the sum of the coefficients in the balanced chemical equation for the combustion of one mole of acetone (C3H6O) in air, we first write the unbalanced equation and then balance it. Unbalanced equation: \[C_{3}H_{6}O(l) + O_{2}(g) \rightarrow CO_{2}(g) + H_{2}O(l)\] Now, we balance the equation: \[C_{3}H_{6}O(l) + \frac{7}{2}O_{2}(g) \rightarrow 3CO_{2}(g) + 3H_{2}O(l)\] To find the sum of coefficients for the balanced equation, we add all the coefficients together, including the coefficients of fractions: Sum of coefficients = 1 (C3H6O) + 7/2 (O2) + 3 (CO2) + 3 (H2O) = 1 + 7/2 + 3 + 3 = 1 + 3.5 + 3 + 3 = 10.5 Therefore, the sum of the coefficients in the balanced chemical equation for the combustion of one mole of acetone in air is 10.5.

Key Concepts

Balanced Chemical Equation

A balanced chemical equation showcases the conservation of mass in a chemical reaction. It ensures that the number of atoms for each element is the same on both sides of the equation. This principle follows the law of conservation of mass, which states that matter cannot be created or destroyed.

Balancing a chemical equation involves adjusting coefficients in front of the chemical formulas. These coefficients represent the relative amounts of each substance involved in the reaction.

• First, write the unbalanced chemical equation for the reaction.
• Identify each type of atom present in the reactants and products.
• Adjust the coefficients to have the same number of each type of atom on both sides.
• Check your work to ensure that all atoms balance out.

Balancing equations prevents errors in the representation of the reaction, ensuring accurate stoichiometric calculations and interpretations.

Hydrocarbon Combustion

Hydrocarbon combustion is a chemical reaction where a hydrocarbon reacts with oxygen to produce carbon dioxide, water, and energy. Hydrocarbons are organic compounds consisting solely of carbon and hydrogen.

During combustion, the carbon atoms from the hydrocarbon combine with oxygen to form carbon dioxide (\(\text{CO}_2\)), while hydrogen atoms combine with oxygen to form water (\(\text{H}_2\text{O}\)). This process releases significant amounts of energy in the form of heat, making it an exothermic reaction.

Examples of hydrocarbons include methane (\(\text{CH}_4\)), propane (\(\text{C}_3\text{H}_8\)), and in this exercise, acetone (\(\text{C}_3\text{H}_6\text{O}\)). Understanding hydrocarbon combustion is crucial in various fields, such as energy production, environmental science, and chemical engineering. This reaction not only supports our everyday needs but also highlights the importance of considering environmental impacts from carbon emissions.

Oxygen as a Reactant

Oxygen is a vital reactant in the process of combustion, providing the necessary chemical environment for hydrocarbons to react and form new compounds. In any combustion reaction, oxygen plays an essential role as it combines with elements of the fuel source, facilitating the reaction.

Commonly found as a diatomic molecule (\(\text{O}_2\)) in air, oxygen is abundant in Earth’s atmosphere, making it readily available for such processes. During combustion, each oxygen molecule bonds with carbon and hydrogen atoms, resulting in the formation of \(\text{CO}_2\) and \(\text{H}_2\text{O}\).

Besides its role in creating new compounds, the presence of oxygen determines the energy outcome of the reaction, as it is directly related to how efficiently the fuel is consumed. Higher efficiency in combustion leads to more energy release and lesser unburnt residues. Understanding oxygen's role aids in optimizing combustion processes and reducing environmental impact.