Question

For which of the following reactions is S° > 0. Choose all that apply. N2(g) + 3H2(g) 2NH3(g) 2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(g) NH4I(s) NH3(g) + HI(g) 2H2O(g) + 2SO2(g) 2H2S(g) + 3O2(g) 2NO(g) + 2H2(g) N2(g) + 2H2O(l) Submit Answer

Answer 1

Answer: $2C_2H_6(g)+7O_2(g)\rightarrow 4CO_2(g)+6H_2O(g)$

$NH_4I(s)\rightarrow NH_3(g)+HI(g)$

$2H_2O(g)+2SO_2(g)\rightarrow 2H_2S(g)+3O_2(g)$

Explanation:

Entropy is the measure of randomness or disorder of a system.

A system has positive value of entropy if the disorder increases and a system has negative value of entropy if the disorder decreases.

1. $N_2(g)+3H_2(g)\rightarrow 2NH_3(g)$

As 4 moles of gaseous reactants are changing to 2 moles of gaseous products,  the randomness is decreasing and the entropy is negative

2. $2C_2H_6(g)+7O_2(g)\rightarrow 4CO_2(g)+6H_2O(g)$

As 9 moles of gaseous reactants are changing to 10 moles of gaseous products,  the randomness is increasing and the entropy is positive.

3. $NH_4I(s)\rightarrow NH_3(g)+HI(g)$

As 1 mole of solid reactants is changing to 2 moles of gaseous products, the randomness is increasing and the entropy is positive.

4. $2H_2O(g)+2SO_2(g)\rightarrow 2H_2S(g)+3O_2(g)$

As 4 moles of gaseous reactants is changing to 5 moles of gaseous products, the randomness is increasing and the entropy is positive

5. $2NO(g)+2H_2(g)\rightarrow N_2(g)+2H_2O(l)$

As 4 moles of gaseous reactants is changing to 1 moles of gaseous products, the randomness is decreasing and the entropy is negative.