# Calculating Heat of Combustion

• ben4life86
In summary, heat of combustion is the amount of heat released when a substance undergoes complete combustion with oxygen. It is typically calculated by measuring the heat released during a controlled combustion reaction and converting it into standard units using thermodynamic principles. The heat of combustion can be affected by factors such as fuel type, oxygen availability, environment temperature and pressure, and impurities in the fuel. It is important to calculate the heat of combustion for understanding energy efficiency and for industrial and environmental applications. In some cases, heat of combustion can be negative if the substance being combusted has a higher energy content than the products of the reaction.

#### ben4life86

A 0.196 g sample of quinone (C6H4O2) is burned in a bomb calorimeter that has a heat capacity of 1.56 kJ/C. What is the heat of combustion (kJ/mol) if the temperature increases by 3.2 C?

-I have no idea how to do this problem...

Look at your text. It has examples of similar problems.

Calculating the heat of combustion involves using the formula Q = mCΔT, where Q is the heat released, m is the mass of the substance, C is the heat capacity of the calorimeter, and ΔT is the change in temperature.

First, we need to convert the mass of quinone from grams to moles. Since the molar mass of quinone is 108.1 g/mol, the moles of quinone in 0.196 g is 0.00181 mol.

Next, we can plug in the values into the formula Q = mCΔT. The mass of quinone is 0.196 g, the heat capacity of the calorimeter is 1.56 kJ/C, and the change in temperature is 3.2 C. This gives us:

Q = (0.196 g)(1.56 kJ/C)(3.2 C) = 0.98 kJ

We now have the heat released, but we need to find the heat of combustion (kJ/mol). To do this, we can use the mole ratio between quinone and the heat released. Since 0.00181 mol of quinone released 0.98 kJ, we can set up a proportion:

0.00181 mol / 0.98 kJ = 1 mol / x kJ

Solving for x, we get x = 540.88 kJ/mol. Therefore, the heat of combustion for quinone is 540.88 kJ/mol.

## 1. What is the definition of heat of combustion?

The heat of combustion is the amount of heat released when a substance undergoes complete combustion with oxygen. It is a measure of the energy stored in a substance's chemical bonds.

## 2. How is heat of combustion calculated?

Heat of combustion is typically calculated by measuring the amount of heat released during a controlled combustion reaction and using the principles of thermodynamics to convert this energy into standard units.

## 3. What factors affect the heat of combustion?

The heat of combustion can be affected by various factors such as the type of fuel, the amount of oxygen available for combustion, the temperature and pressure of the environment, and the type and amount of impurities present in the fuel.

## 4. Why is it important to calculate heat of combustion?

Calculating the heat of combustion is important for understanding the energy efficiency of a substance or fuel. It can also be used to determine the amount of energy released during a combustion reaction, which is important for various industrial and environmental applications.

## 5. Can heat of combustion be negative?

Yes, heat of combustion can be negative in cases where the substance being combusted has a higher energy content than the products of the reaction. This can occur with certain fuels or in situations where the combustion is not complete.