Answer:
(i) ΔS° < 0 or negative
(ii) ΔS° > 0 or positive
(iii) ΔS° > 0 or positive
(iv) ΔS° > 0 or positive
(v) ΔS° < 0 or negative
(vi) ΔS° > 0 or positive
Explanation:
Entropy is a state function and extensive property of the system.
It's the measurement of degree of randomness..
Entropy of the system decreases as follows
Gas > Liquid > Amorphous solid > Crystalline solid.
In case for chemical reaction
(i) Ba²⁺ (aq) + SO₄²⁻ (aq) --> BaSO₄ (s)
Total entropy change ΔS° < 0 or negative
During this reaction aqueous i.e liquid phase converted into solid phase.
So randomness decreases and hence entropy also decreases.
(ii) 2 NO₂ (g) --> N₂ (g) + 2 O₂ (g) ΔS° > 0 or positive
Since no. of gaseous moles increases from reactants to products.
(iii) C₅H₁₂ (g) + 8 O₂ (g) --> 5 CO₂ (g) + 6 H₂O (g) ΔS° > 0 or positive
Since no. of gaseous moles increases from reactants to products.
(iv) 2 NaClO₃ (s) --> 2 NaCl (s) + 3 O₂ (g) ΔS° > 0 or positive
Since no. of gaseous moles increases from reactants to products.
(v) 2 Na (s) + Cl₂ (g) --> 2 NaCl (s) ΔS° < 0 or negative
Since no. of gaseous moles decreases from left to right so entropy also decreases.
(vi) CH₃OH (l) --> CH₃OH (g) ΔS° > 0 or positive
Because during this phase transition Liquid to gaseous randomness increases and hence entropy also increases.