Q.In an exothermic reaction, heat is evolved, and system loses heat to the surrounding. For such system (Note: more than one of the given options may be correct.)

Bomb Calorimetry and Enthalpy: From Intuition to Precision

Imagine you want to know exactly how much heat a handful of cashews releases when your body burns it. You could eat them and measure your temperature rise — but that’s messy, slow, and full of biological noise. A bomb calorimeter is the chemist’s clean, controlled way to do the same thing: burn a sample completely in pure oxygen inside a sealed steel container (the “bomb”) submerged in water, and measure the temperature change of that water.

The key insight: everything stays at constant volume. The bomb is rigid — it doesn’t expand or contract. That single fact changes which thermodynamic quantity you measure directly.

What the bomb actually measures

When the sample burns, it releases heat. That heat warms the bomb, the water, and everything around it. From the temperature rise and the known heat capacity of the entire calorimeter, you calculate the heat released at constant volume, denoted $q_V$.

For any process at constant volume with no non-expansion work (like electrical work), the first law of thermodynamics says:

$q_V = \Delta U$

where $\Delta U$ is the change in internal energy of the system (the burning sample + oxygen + products). So a bomb calorimeter directly gives you $\Delta U$ for the combustion reaction. …