i. The most stable and unstable compounds are

Question

ΔG0_f for CuS, CaS, SO₂ , CS₂ & CuO are -49, -1230, -300.4, +63.6 & - 127.2 KJ/ mol-1 respectively.

i.   The most stable and unstable compounds are 

(A)  SO₂ & CaS 

(B)  CaS & CS₂ 

(C)  CuS & SO₂ 

(D)  CaS & SO₂ 

ii.   CuS & CaS are reduced with Carbon to give Cu or Ca and CS₂ . The reaction which will be spontaneous is 

(A)  Reduction of CuS because DG is positive

(B)  Reduction of CaS because  ΔG is negative 

(C)  Both are spontaneous because  ΔG is positive 

(D)  Both are non spontaneous because ΔG is positive

iii.   The ΔG0 for the reaction 2CuS + 3O₂  → 2CuO + 2SO₂ is ____  & the reaction is _____

(A)   – 756.8KJ & Spontaneous 

(B)   +756.8KJ & non- Spontaneous 

(C)   -378.4KJ & Spontaneous 

(D)   +378.4 KJ & non-Spontaneous 

(a)   i-B, ii-D, iii-A

(b)   i-D, ii-C, iii-B 

(c)   i-B, ii-D, iii-C 

(d)   i -C, ii-B, iii-D

Answer 1

(b)  i-D, ii-C, iii-B