Δs is positive for the reaction a.2no (g) + o2 (g) → 2no2 (g) b.2n2 (g) + 3h2 (g) → 2nh3 (g) c. c3h8 (g) + 5 o2 (g) → 3co2 (g) + 4 h2o (g) d. mg (s) + cl2 (g) → mgcl2 (s) e. c2h4 (g) + h2 (g) → c2h6 (g)

Option (c) is the correct answer.

Explanation:

Entropy means the degree of randomness present in a substance or within the reactants in a chemical reaction.

Change in entropy is represented by . More is the degree of randomness present more positive will be the value of . Similarly, less is the degree of randomness present within a substance lesser will be the value of .

(a)    

Here, 3 moles of reactants are giving 2 moles of product. Hence, entropy is decreasing so, the value of is negative.

(b)  

Here, 5 moles of reactants are giving 2 moles of product.  Hence, entropy is decreasing so, the value of is negative.

(c)  

Here, 6 moles of reactants are giving 7 moles of product.  Hence, entropy is increasing so, the value of is positive.

(d)

Here, 2 moles of reactants are giving 1 mole of product.  Hence, entropy is decreasing so, the value of is negative.

(e)  

Here, 2 moles of reactants are giving 1 mole of product.  Hence, entropy is decreasing so, the value of is negative.

Thus, we can conclude that is positive for the reaction .