Djdj Which one of the following is always positive when a spontaneous process oc

Question

Djdj Which one of the following is always positive when a spontaneous process occurs? Delta S surroundings Delta S System Delta H universe Delta H surroundings Delta S universe Delta S is positive for the reaction 2Hg(l) + O2(g) right arrow 2HgO(s) 2H2(g) + O2(g) right arrow 2H_2O(g) BaF2 (s) right arrow Ba^2 + (aq) + 2F^- (aq) CO_2 (g) right arrow CO_2 (s) 2NO2(g) right arrow N2O4 (g) Which reaction produces a decrease in the entropy of the system? UF6 (s) right arrow U(s) + 3F2 (g) 2 HgO (s) right arrow 2 Hg (I) + O2(g) H_2O (s) right arrow H_2O (g) 4 NH3 (g) + 5 O2(g) right arrow 4NO(g) + 6 H_2O (g) Na (s) + 1/2 CI2 (g) right arrow NaCl (s)

Explanation / Answer

14) Ans: E

Second law of thermodynamics - All spontaneous processes associated with entropy of the universe.

Therefore, Suniverse is always positive in spontaneous process.

15) Ans: C

Entropy is the measure of disorderness of the system.

Therefore,

Order of entropy : gases > liquids > solids

BaF2(s) -----------> Ba2+ (aq) + 2F- (aq)

s ----------> aq + aq

Since aqueous (liquid) molecules have more entropy than solids, in this reaction entropy increases.

Therefore, S is positive.

16) Ans: E

Na(s) + (1/2) Cl2(g) ------------> NaCl (s)

s + g --------------> s

solid+gas system is more disordered than solid system.

So, in this reaction entropy decreases.

(Therefore, S is negative)

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