Question

Correct option for an endothermic gaseous reaction
A+B —3C will be
(1) H > 0; S <0 (2) H = 0; S > 0
(3) H > 0; S >O (4) H = 0; S < 0​

Answer 1

Answer: (3) H > 0; S >O

Explanation:

Endothermic reactions are those in which heat is absorbed by the system and exothermic reactions are those in which heat is released by the system.

$\Delta H$ for Endothermic reaction is positive and $\Delta H$ for Exothermic reaction is negative.

Entropy is the measure of randomness or disorder of a system. If a system moves from  an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.

$\Delta S$ is positive when randomness increases and $\Delta S$ is negative when randomness decreases.

For the given gaseous reaction:

$A(g)+B(g)\rightarrow 3C(g)$                                                

As the number of moles of products is more than the number of moles of reactants, the entropy is increasing,  $\Delta S=+ve$

$\Delta H$ is positive for endothermic reaction.

Thus H > 0 and  S > 0.

Answer 2

Explanation:

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