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Phenol, a chemical compound with the formula \( \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} \), undergoes a combustion reaction when it reacts with oxygen in the air. This process is crucial in the study of calorimetry, as it helps us understand how energy is released. During combustion, phenol reacts with oxygen to form carbon dioxide \( \mathrm{CO}_{2} \) and water \( \mathrm{H}_{2}\mathrm{O} \). The equation for this reaction is initially unbalanced:

• \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} + \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O}\)

To balance it, we need to ensure that there are equal numbers of each type of atom on both sides of the equation. The balanced equation is then written as:

• \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} + 7\mathrm{O}_{2} \rightarrow 6\mathrm{CO}_{2} + 3\mathrm{H}_{2}\mathrm{O}\)

This balanced equation now represents complete phenol combustion, which is essential to accurately calculate the energy released in this exothermic reaction.

When studying calorimetry, understanding heat capacity is vital. Heat capacity is a measure of the amount of heat needed to change the temperature of a system by one degree Celsius. In the context of this exercise, the bomb calorimeter, used to study the combustion of phenol, has a heat capacity of \( 11.90 \mathrm{~kJ}/{ }^{\circ} \mathrm{C} \).

• It's an extensive property, meaning it depends on the size or amount of the material in the system.
• The calorimeter absorbs the heat released during phenol combustion, causing its temperature to change.

To calculate the total heat gained by the calorimeter, use the formula:

• Total heat gained = Heat capacity × Temperature change

Here, the temperature change is \( 6.00 \mathrm{~^{\circ}C} \) (from \( 21.50^{\circ} \mathrm{C} \) to \( 27.50^{\circ} \mathrm{C} \)), resulting in a calculated heat gain of \( 71.40 \mathrm{~kJ} \). This information helps us determine the energetic properties of phenol when burned.

Writing a balanced chemical equation is a fundamental skill in chemistry, necessary for accurately describing chemical reactions. When working on the combustion of phenol, balancing the equation ensures that the law of conservation of mass applies, meaning the same number of each type of atom appears on both sides.

• Start with the skeleton equation: \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} + \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O}\).
• Identify the number of each atom on both sides, then adjust coefficients to balance them.

For phenol combustion, balancing results in:

• \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} + 7\mathrm{O}_{2} \rightarrow 6\mathrm{CO}_{2} + 3\mathrm{H}_{2}\mathrm{O}\).

It's crucial for subsequent calculations, like determining reactant quantities and the energy involved. Ensure accuracy in balancing to get reliable results in calorimetry assessments.

Calculating molar mass involves determining the mass of one mole of a substance, expressed in grams per mole \(\text{g/mol}\). For phenol \( \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH} \), follow these steps:

• Identify the molar masses: carbon (C) is \(12.01\,\text{g/mol}\), hydrogen (H) is \(1.01\,\text{g/mol}\), and oxygen (O) is \(16.00\,\text{g/mol}\).
• Calculate the total molar mass:

\[ 6 \times 12.01\, \text{g/mol} + 5 \times 1.01\, \text{g/mol} + 16.00\, \text{g/mol} + 1.01\, \text{g/mol} = 94.11\, \text{g/mol}\]Understanding molar mass is crucial because it links the mass of phenol to the number of moles, which is essential for calculating the energy of combustion per mole. In this exercise, multiplying the heat of combustion per gram by the molar mass gives the heat of combustion per mole, aiding in understanding the energy dynamics of phenol.