Sulphide ores of metals are usually concentrated by the froth flotation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

1. Argentite

2. Galena

3. Copper pyrite

4. Sphalerite

The efficiency of a fuel cell is given by:

1. $\frac{∆H}{∆G}$

2. $\frac{∆G}{∆S}$

3. $\frac{∆G}{∆H}$

4. $\frac{∆S}{∆G}$

The compound on hydrolysis of 50% aqueous sodium hydroxide that produces the corresponding alcohol and acid is:

1. $C_6{H}_{5}C{H}_{2}CHO$

2. $C_6{H}_{5}CHO$

3. $C{H}_{3}C{H}_{2}C{H}_{2}CHO$

4. ${\mathrm{CH}}_3-\stackrel{\mathrm{O}}{\stackrel{\left|\right|}{\mathrm{C}}}-{\mathrm{CH}}_3$

Identify the correct order of the size of the following:

1. $C{a}^{2+}<K^{+}<Ar<S^{2-}<C{l}^{-}$

2. $C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$

3. $Ar<C{a}^{2+}<K^{+}<C{l}^{-}<S^{2-}$

4. $C{a}^{2+}<A{r}^{+}<K^{+}<C{l}^{-}<S^{2-}$

Consider the following compounds:

(i)	C6H5COCl	(ii)
(iii)		(iv)

What is the correct decreasing order of their reactivity towards hydrolysis?

1. (ii) > (iv) > (iii) > (i)

2. (i) > (ii) > (iii) > (iv)

3. (iv) > (ii) > (i) > (iii)

4. (ii) > (iv) > (i) > (iii)

The product formed in aldol condensation is:

If NaCl is doped with 10^-4mol% of SrCl₂, the concentration of cation vacancies will be (N_A= 6.02×10²³mol^-1):

1. $6.02\times {10}^{15}$ $mo{l}^{-1}$

2. $6.02\times {10}^{16}$ $mo{l}^{-1}$

3. $6.02\times {10}^{17}$ $mo{l}^{-1}$

4. $6.02\times {10}^{14}$ $mo{l}^{-1}$

The d-electron configurations of Cr²⁺, Mn²⁺, Fe²⁺ and Ni²⁺ and 3d⁴, 3d⁵, 3d⁶ and 3d⁸ respectively.
Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour? 
(At. No. Cr = 24, Mn = 25, Fe = 26, Ni = 28)

1. \(\left[\mathrm{Mn}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
2. \(\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
3. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
4. \(\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)

The order of decreasing reactivity towards an electrophilic reagent, for the following 
(i) Benzene
(ii) Toluene 
(iii) Chlorobenzene  
(iv) Phenol
would be: 

1. (i) > (ii) > (iii) > (iv)

2. (ii) > (iv) > (i) > (iii)

3. (iv) > (iii) > (ii) > (i)

4. (iv) > (ii) > (i) > (iii)

Select the pair of isostructural species.