How is Heat of Combustion Measured Indirectly, Lab Report Example

The heat of combustion is precisely referred to as enthalpy of combustion and normally given the symbol H. It is used hand in hand with the precise term enthalpy of combustion. During this reaction, one mole of substance reacts with oxygen to form an oxidized form of the given element of a substance, such as atoms of carbon change to carbon dioxide, and sulfur atoms changed to sulfur dioxide. As a result the goal of the experiment is realized indirectly though the determination of heat of combustion (H). Just like all enthalpies, H is known as the heat absorbed by a mole of a given substance to undergo the reaction under three steps at constant pressure; work possible occurring in expansion against the atmosphere, and a stage of constant temperature.

During practical, there is an increase in temperature due to combustion reaction. Additionally, it is experimentally preferred to use a fastened bottle with a constant volume in caring out combustion reaction. Thus, H calculated from qualities that are measured directly, but it cannot be measured directly.

In the determination of H, an amount of substance in a sealed container would be combusted and immersed in a water bath. The heat released during combustion increases the temperature of water, and the comb calorimeter. While the reaction proceeds, the pressure in the calorimeter changes due to the change in temperature same to mole numbers of gas in relation to the stoichiometric reaction of combustion. The change in energy from the reaction is calculated using the change in temperature, and capacities of heat of the bathwater, and calorimeter takeaway whatever energy was used at the beginning of the combustion. H is hence calculated by adding the PV work often referred to as nRT. This experiment/calorimetric technique adheres to the Hess’ law of energy conservation where the total heat used in combustion is equivalent to the heat used for the entire reaction; irrespective of the path taken, the H is the same. The sealing of the container in this experiment plays a critical role in energy conservation by minimizing wastage.