Test: Internal Energy - Chemistry MCQ

The heat that is emitted or absorbed at a constant volume is the internal energy.

The internal energy of a definite amount of a particular substance under given conditions of temperature and pressure always has a definite value.

According to the first law of thermodynamics, ΔE = q + w
Where q is either heat absorbed or given out by the system.
W is the work done on or by the system.

For Isochoric change, ΔV = 0 w = PΔV = 0 S
ince, ΔE = q + w
This implies, ΔE = q

As we know that, ΔH = ΔU + Δn_gRT
Where Δn_g denotes the stoichiometric difference between the gaseous products and the gaseous reactants.

Hence for reaction c) ΔH = ΔU as Δn_g = 0.

For isochoric processes, ΔV = 0, so q_V = ΔE i.e, heat given to a system under constant volume is used up in increasing ΔE.

When the temperature remains constant, isothermal expansion occurs. This suggests that ΔT = 0. Additionally, since internal energy depends on temperature, isothermal expansion results in zero internal energy.

Internal energy is the sum of all different types of energies associated with atoms and molecules such as electronic energy, nuclear energy, chemical bond energy, potential energy and kinetic energy. Gravitational energy is not the part of Internal energy.

Since, the ΔU is a function of temperature and volume,

In isothermal process, Temperature is constant so ΔU=0

and in isochoric process, volume is constant so ΔU=0

and in cyclic process, after one complete cycle the system returns to its original state, so ΔU=0