Which of the following are unstable with respect to their constituent elements a

Question

Which of the following are unstable with respect to their constituent elements at 25°C? Species -f kJ/mollarf kJ/mols",l(K-mol) C8H18 0) C2H2 ()+227 CH3OH1-239 -250 +329 201 +127 +6 +209 -166 A) C8H18(0), C2H2(g) C) C2H2(8) B) GHisin, CH3011 D) CI 1301 1(r) 8) Which has the lowest entropy? B) CH3OHQ, 16°c) D) CH30Hs, -26°C) A) CH30H(0, 30°C) C) CH3OHs,-13°C) 9) Which of the following statements must be true for the entropy of a pure solid to be zero? L The temperature must be 0 K. I. The solid must be crystalline, not amorphous. ml. The solid must be perfectly ordered. The solid must be an element. D) I, ILIll, and rv B) I and II C) L, II, and III A)I 10) 10) Which has the highest standard molar entropy at 25°C? D) F2(g) C) 12(8) A) N2(g) 11) . 11) what is the entropy change associated with the expansion of one mole of an ideal gas from an initial volume of V to a final volume of V of 2.50V at constant temperature? A) AS -250 R In (VeVi) D) AS-2.50 R In (Viv) C)AS -R In 2.50 12) For a particular battery based on one of the following reactions, E is expected to remain constant with time until the cell reactants are almost completely consumed. Which is the appropriate reaction? A)/t (s) + PO2(s) + 2 H.(aq) + 2 HS04-(aq) 2 PbO4(s) +2H20) B) 2 NiOOH)(s) + Cd(s) + 2 H2O() 2 Ni(OH)2(s) . Cd(0H2(s) C) Zn(s) + 2 MnO2(s) + 2 NH4+(ag) 2 NH3(aq) + Mn2O3(s) . Zn2.(aq) + H201) D) Zn(s) + Cu2+(aq) Zn2.(aq) + Cu(s) A-2

Explanation / Answer

7)

delta G is positive for C2H2 (l)

So, formation of C2H2 (l) is not spontaneous

SO, this is unstable as the backward reaction is spontaneous and C2H2(l) can convert into constituent elements.

Answer: C

8)

solid have least entropy.

Also the one with lower temperature will have least entropy

This is because lower temperature implies less vibration and hence less randomness and hence less entropy

Answer: D

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