In the extraction of copper from its sulphide ore, the metal is finally obtained by the reduction of cuprous oxide with?

1. Iron(II) sulphide

2. Carbon monoxide

3. Copper(I) sulphide

4. Sulphur dioxide

Which one of the following pairs of solutions is not an acidic buffer?

1. ${\mathrm{HClO}}_4$ $\mathrm{and}$ ${\mathrm{NaClO}}_4$
2. ${\mathrm{CH}}_3\mathrm{COOH}$ $\mathrm{and}$ ${\mathrm{CH}}_3\mathrm{COONa}$
3. ${\mathrm{H}}_2{\mathrm{CO}}_3$ $\mathrm{and}$ ${\mathrm{Na}}_2{\mathrm{CO}}_3$
4. ${\mathrm{H}}_3{\mathrm{PO}}_4$ $\mathrm{and}$ ${\mathrm{Na}}_3{\mathrm{PO}}_4$

Assuming complete ionization, same moles of which of the following compounds will require the least amount of acidified KMnO₄ for complex oxidation?

1. $FeS{O}_4$

2. $FeS{O}_3$

3. $Fe{C}_2{O}_4$

4. $Fe{\left(N{O}_2\right)}_2$

The number of structural isomers possible from the molecular formula C₃H₉N are:

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g of magnesium oxide.
The percentage purity of magnesium carbonate in the sample is: 
(Atomic weight of Mg=24)

Two possible stereo-structures of CH₃CHOH.COOH, that are optically active, called:

The heat of combustion of carbon to CO₂ is –393.5 KJ/mol. The heat released upon the formation of 35.2 g of CO₂ from carbon and oxygen gas is:

The rate Constant of reaction A → B is 0.6 × 10^–3 \(\mathrm{molL}^{-1} \mathrm{~S}^{-1}\). If the Concentration of A is 5M, then the concentration of B after 20 min is:

1. 1.08M

2. 3.60M

3. 0.36M

4. 0.72M

The formation of the oxide ion, O²⁻(g), from an oxygen atom occurs in two successive steps:

O(g) + e⁻ → O⁻(g)  ΔH = −141 kJ mol⁻¹

O⁻(g) + e⁻ → O²⁻(g)  ΔH = +780 kJ mol⁻¹

Although O²⁻ is isoelectronic with neon, its formation in the gaseous state is energetically unfavourable. What is the main reason for this?

What is the mass of the precipitate formed when 50 mL of 16.9% solution of AgNO₃ is mixed with 50 mL of 5.8% NaCl solution? (Ag = 107.8, N = 14, O = 16, Na= 23, Cl = 35.5)
1. 28 g
2. 3.5 g
3. 7 g
4. 14 g