Why don't we use the bomb calorimeter to calculate the heat energy in the combustion of alcohol but we use the copper cup calorimeter?
To understand why we don't use a bomb calorimeter to calculate the heat energy in the combustion of alcohol, let's first discuss what these two types of calorimeters are and how they work.
A calorimeter is a device used to measure the heat energy change that occurs during a chemical reaction, such as combustion. The bomb calorimeter and the copper cup calorimeter are two commonly used types of calorimeters.
The bomb calorimeter is designed to measure the heat released or absorbed during a combustion reaction under constant volume conditions. It consists of a bomb-shaped container made of stainless steel, which is strong enough to withstand high pressure. The substance being studied is placed inside the bomb along with excess oxygen, and the reaction is ignited by a spark. As the combustion occurs, heat is released and transferred to the surrounding water, which then undergoes a temperature change. By measuring this temperature change, we can calculate the heat energy of the reaction.
On the other hand, the copper cup calorimeter is designed to measure the heat released or absorbed during a reaction under constant pressure conditions. It consists of a copper container, often in the shape of a cup, filled with a known amount of water. The substance being studied is added to the water, and its combustion is initiated. Heat is released and transferred to the water, causing its temperature to rise. By measuring the temperature change of the water, we can calculate the heat energy of the reaction.
Now, coming back to the original question, we generally prefer to use the copper cup calorimeter for measuring the heat energy in the combustion of alcohol rather than a bomb calorimeter. This is because the combustion of alcohol occurs more naturally under constant pressure rather than constant volume conditions.
In the copper cup calorimeter, the combustion occurs in an open container, allowing the reaction to maintain a constant atmospheric pressure while releasing heat energy. This more closely resembles real-world scenarios where substances usually combust in open air at atmospheric pressure.
Alternatively, in a bomb calorimeter, the reaction takes place in a closed, high-pressure vessel, creating constant volume conditions. This setup is not suitable for the combustion of alcohol because alcohol generally burns in open air at atmospheric pressure.
So, to summarize, the choice of using a copper cup calorimeter over a bomb calorimeter for measuring the heat energy in the combustion of alcohol is based on the fact that alcohol combustion typically occurs under constant pressure rather than constant volume conditions.