Flashcards for NEET Chemistry - Thermodynamics

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Chemistry

Thermodynamics

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Thermodynamics

The First Law of Thermodynamics

The law of conservation of energy

The energy of an isolated system is constant

∆U = q + w; for an isolated system, w = 0 and q = 0, then ∆U = 0

Enthalpy

It is the sum of its internal energy and the product of its pressure and volume

H = U + pV

Enthalpy Change

It is the difference in enthalpy of the reactants and products (∆H)

At constant pressure:

∆H = ∆U + p∆V = q_p

∆H is negative for exothermic reactions

∆H is positive for endothermic reactions

At constant volume: ∆H = ∆U = q_v

Extensive Property

Its value depends on the quantity or size of matter present in the system

E.g. mass, volume, internal energy, enthalpy, heat capacity, etc.

Intensive Property

Its value does not depend on the quantity or size of matter present in the system

E.g. temperature, density, pressure, etc.

Specific Heat Capacity

The quantity of heat required to raise the temperature of one unit mass of a substance by one degree celsius or one kelvin

Heat Capacity

Heat capacity at constant pressure is C_p, and the heat capacity at constant volume is C_v

q_p = C_p∆T = ∆H

q_v = C_v∆T = ∆U

C_p – C_V = R

Entropy

A measure of the degree of randomness or disorder in the system, denoted by ’S’

For a reversible reaction, change in entropy ∆S = q_rev/T

For a spontaneous reaction, change in entropy ∆S_total = ∆S_system + ∆S_surr > 0

Gibbs Energy

It is an extensive property and a state function, denoted by G

The change in Gibbs energy for the system is

∆G = ∆H − T∆S

If ∆G is negative (< 0), the process is spontaneous

At equilibrium, ∆G = 0

Second Law of Thermodynamics

The entropy of an isolated system increases in the course of a spontaneous change

∆S_total > 0

Also Check:

• NEET Chemistry Syllabus
• NEET Chemistry Important Topics
• NEET Chemistry MCQs
• How to Score 160 Plus in NEET Chemistry