Burning acetylene in oxygen can produce three different carbon-containing products: soot (very fine particles of graphite), CO(g), and CO2(g). (a) Write three balanced equations for the reaction of acetylene gas with oxygen to produce these three products. In each case assume that H2O(l) is the only other product. Determine the standard enthalpies for the reactions in part (a).

Verified step by step guidance

1. Step 1: Write the balanced chemical equation for the complete combustion of acetylene (C2H2) to produce carbon dioxide (CO2) and water (H2O). The general form is: C2H2 + O2 -> CO2 + H2O. Balance the equation by ensuring the number of atoms of each element is equal on both sides.
2. Step 2: Write the balanced chemical equation for the incomplete combustion of acetylene to produce carbon monoxide (CO) and water (H2O). The general form is: C2H2 + O2 -> CO + H2O. Balance the equation by adjusting the coefficients to ensure the conservation of mass.
3. Step 3: Write the balanced chemical equation for the combustion of acetylene to produce soot (graphite, C) and water (H2O). The general form is: C2H2 + O2 -> C + H2O. Balance the equation by ensuring the number of carbon, hydrogen, and oxygen atoms are equal on both sides.
4. Step 4: Determine the standard enthalpy change (ΔH°) for each reaction. Use standard enthalpy of formation values from a data table for each reactant and product. Apply Hess's Law: ΔH° = ΣΔH°f(products) - ΣΔH°f(reactants).
5. Step 5: Calculate the standard enthalpy change for each reaction using the balanced equations and the standard enthalpy of formation values. This involves substituting the values into the equation from Step 4 and performing the arithmetic to find ΔH° for each reaction.

Key Concepts

Combustion Reactions

Combustion reactions involve the reaction of a fuel with an oxidant, typically oxygen, resulting in the release of energy. In the case of acetylene (C2H2), it can combust completely to form carbon dioxide (CO2) and water (H2O), or partially to produce carbon monoxide (CO) and soot. Understanding the stoichiometry of these reactions is essential for writing balanced chemical equations.

Balancing Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is upheld. This involves adjusting the coefficients of reactants and products so that the number of atoms of each element is the same on both sides of the equation. For the combustion of acetylene, this means carefully counting and adjusting the carbon, hydrogen, and oxygen atoms to reflect the products formed.

Standard Enthalpy of Reaction

The standard enthalpy of reaction (ΔH°) is the heat change that occurs when reactants are converted to products under standard conditions (1 atm pressure and 25°C). It is crucial for understanding the energy changes associated with chemical reactions, including combustion. Calculating ΔH° for the combustion of acetylene requires knowledge of the enthalpies of formation for the reactants and products involved.