In an experiment to measure the enthalpy change of a reaction involving gases,
which of the following conditions must always be kept constant?
D )Temperature and pressure
Enthalpy or heat content of a gaseous system is defined as the sum of the internal energy and the product of its pressure volume.
H = E + PV
Where, E is the internal energy, P is the constant pressure, and V is the volume of the system.
Change in enthalpy ∆H, is defined as the amount of energy exchanged with the surroundings at constant pressure and temperature.
It is expressed as: ∆H = ∆E + P∆V
An apparently similar term, change in energy at constant volume is known as internal energy change ∆E.
Hence the right option here, is thus D).