Question

Which of the following reactions is associated with an increase in entropy?
(A) \[{N_2}(g) + 3H{ _2}(g) \to 2N{H_3}(g)\]
(B) $2{H_2}(g) + {O_2}(g) \to 2{H_2}O(l)$
(C) ${H_2}(g) + {I_2}(g) \to 2HI(g)$
(D) $C(graphite) + {H_2}O(g) \to CO(g) + {H_2}(g)$ systemic

Answer 1

Hint: To find the increase in entropy, we must know if the given reaction is exothermic or endothermic. The external energy increases in the exothermic reaction and in the endothermic reaction it decreases. Free energy is a measure of the capacity of the system to do work. Free energy takes into account both entropy and entropy changes that occur as a result of heat exchange with the environment.

Complete Step by Step Solution:
System entropy increases whenever its particles have more freedom of movement.
Therefore, entropy increases whenever you have more molecules of gas products than reactants and whenever you have more product particles in solution than reacting particles.

Thus between a given reaction, an increase in entropy is associated. Therefore it is an exothermic reaction.
$C(graphite) + {H_2}O(g) \to CO(g) + {H_2}(g)$ systemic
As the reaction side has only one gas particle while the product side has two gas particles.
Therefore, entropy is increasing.

So, the correct answer is D) $C(graphite) + {H_2}O(g) \to CO(g) + {H_2}(g)$ systemic.

Note: Entropy and enthalpy are two basic elements of thermodynamics. Enthalpy has to do with the powerful content of a system or molecule. Entropy has to do with how that energy is stored. Response is preferred when the enthalpy is reduced: There is a bias in nature in reducing the enthalpy in the system. Reactions can occur when the enthalpy is transmitted to the environment. The reaction is favourable when the entropy increases. There is also a natural bias in increasing the entropy in the system. Reactions can occur as entropy increases.