Question

Balance the following reaction and use the equation to calculate the ΔHrxn. C₃H₈(g) + O₂(g) → CO₂(g) + H₂O(g) Round your answer to the nearest whole number. ΔHrxn=kJ/mole

Answer 1

The balanced chemical equation for the given reaction is:

`\[ \mathrm{C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)} \]`

The calculated ΔHrxn for the reaction is
`\(\Delta Hrxn = -2044 \, \mathrm{kJ/mol}\)`, rounded to the nearest whole number.

Step-by-step explanation:

In order to balance the chemical equation, one must ensure that the number of atoms for each element on both the reactant and product sides is the same. In this case, balancing the equation yields:
`\(\Delta Hrxn = -2044 \, \mathrm{kJ/mol}\)`

`\[ \mathrm{C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)} \]`

This means that for every mole of propane
`(\(C_3H_8\))`reacting with oxygen
`(\(O_2\)),` three moles of carbon dioxide
`(\(CO_2\))` and four moles of water
`(\(H_2O\))` are produced.

To calculate the enthalpy change
`(\(\Delta Hrxn\))` , we can use the bond enthalpy values. The bond enthalpy of the reactants minus the bond enthalpy of the products gives the overall enthalpy change. For this reaction:

`\[ \Delta Hrxn = \sum \text{(bond enthalpies of bonds broken)} - \sum \text{(bond enthalpies of bonds formed)} \]`

Substituting the values and calculating, we find
`\(\Delta Hrxn = -2044 \, \mathrm{kJ/mol}\).` The negative sign indicates an exothermic reaction, releasing energy to the surroundings. In conclusion, the balanced equation ensures the conservation of mass, and the calculated
`\(\Delta Hrxn\)` quantifies the heat energy released per mole of reactant consumed in the reaction. The negative value signifies the release of energy, a characteristic of exothermic reactions.