Which process is expected to have an increase in entropy?

Question:

Which process is expected to have an increase in entropy?

(a) Decomposition of N_2O_4 gas to NO_2 gas

(b) Formation of liquid water from hydrogen and oxygen gas.

(c) Precipitation of BaSO_4 from mixing solutions of BaCl_2 and Na_2SO_4

(d) Iron rusting

Answer:

The correct option are;

(a) The decomposition of N₂O₄ into NO₂ gas and

(d) Iron rusting

Explanation:

The entropy S is defined as measure of the thermal energy within a system that cannot be used to do work. It is the degree of randomness or disorder of the particles of the system.

(a) The decomposition of N₂O₄ into NO₂ is as follows

N₂O₄ (g) → 2 NO₂ (g)

Here we have one mole of reactants leading to two moles of products, hence there is an increase in randomness hence increase in entropy

(b) Formation of liquid water from hydrogen and oxygen gas.

This is a decrease in entropy from gs to liquid

(c) Precipitation of BaSO₄ from mixing solutions of BaCl₂ and Na₂SO₄

Here we have a reduction in entropy due to formation of a solid from aqueous substances

(d) Iron rusting

This is a spontaneous process where both the iron and the rust particles are solids, although there is an increase in disorderliness, hence increase in entropy.

High entropy means high disorder and low energy.

So a system with gas expansion, increase in temperature and pressure, increases entropy.

Explanation:

Entropy is defined as the quantitative measure of disorder or randomness in a system. The concept comes out of thermodynamics, which deals with the transfer of heat energy within a system.

Entropy, the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, the amount of entropy is also a measure of the molecular disorder, or randomness, of a system