The enthalpy of combustion (ΔH°c) of methane, CH4(g), is -890.5 kJ/mol, and the standard enthalpy of formation (ΔH°f) of ozone, O3(g), is 143 kJ/mol. The reaction between ozone and methane produces CO2 and water. The heat produced in a complete reaction of 0.2 mol of CH4 with ozone under standard conditions is …. kJ.
The Correct Answer and Explanation is:
To calculate the heat produced in a complete reaction of 0.2 mol of methane (CH4) with ozone (O3) under standard conditions, we need to use the concept of enthalpy change, specifically the standard enthalpy of combustion of methane and the standard enthalpy of formation of ozone. The enthalpy change for the reaction will depend on the bond energies and the changes in enthalpy for the reactants and products.
Step 1: Write the balanced chemical equation for the reaction
The complete combustion of methane in the presence of ozone can be represented by the following reaction:CH4(g)+2O3(g)→CO2(g)+2H2O(g)CH_4(g) + 2 O_3(g) \rightarrow CO_2(g) + 2 H_2O(g)CH4(g)+2O3(g)→CO2(g)+2H2O(g)
This equation assumes that methane reacts with ozone to form carbon dioxide and water.
Step 2: Use the given enthalpy values
- The standard enthalpy of combustion of methane (ΔH°c) is -890.5 kJ/mol. This value indicates the heat released when 1 mol of CH4 undergoes complete combustion.
- The standard enthalpy of formation of ozone (ΔH°f) is 143 kJ/mol. This represents the heat required to form 1 mol of ozone from its elements in their standard states.
Step 3: Calculate the total heat released
To determine the total heat released when 0.2 mol of CH4 reacts, we need to use the standard enthalpy of combustion of methane, as it will be the primary contributor to the heat change.
The heat released when 1 mol of CH4 reacts with ozone is -890.5 kJ. Therefore, when 0.2 mol of CH4 reacts, the heat released will be:Heat released=(−890.5 kJ/mol)×0.2 mol=−178.1 kJ\text{Heat released} = \left( -890.5 \, \text{kJ/mol} \right) \times 0.2 \, \text{mol} = -178.1 \, \text{kJ}Heat released=(−890.5kJ/mol)×0.2mol=−178.1kJ
Step 4: Conclusion
Thus, the heat produced in a complete reaction of 0.2 mol of CH4 with ozone under standard conditions is -178.1 kJ. This negative value indicates that the reaction is exothermic, meaning that it releases energy.
