General Principles of Isolation of Elements · Question 11

"Metals are usually not found as nitrates in their ores." Out of the following two (I and II) reasons which is/are true for the above observation? I. Metal nitrates are highly unstable. II. Metal nitrates are highly soluble in water.

1. I is false but II is true.
2. I is true but II is false.
3. I and II are true.
4. I and II are false

The metal oxide which cannot be reduced to metal by carbon is

1. Al2O3
2. PbO
3. ZnO
4. Fe2O3

The Gibbs energy for the decomposition of Al2O3 at 500 is as follows 23Al2O3 43Al + O2 rG = +960 kJ mol-1 The potential difference needed for the electrolytic reduction of aluminium oxide (Al2O3) at 500 is at least

1. 4.5 V
2. 3.0 V
3. 2.5 V
4. 5.0 V

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

1. carbon monoxide
2. copper (I) sulphide
3. sulphur dioxide
4. iron (II) sulphide.

Aluminium is extracted from alumina (Al2O3) by electrolysis of a molten mixture of

1. Al2O3 + HF + NaAlF4
2. Al2O3 + CaF2 + NaAlF4
3. Al2O3 + Na3AlF6 + CaF2
4. Al2O3 + KF + Na3AlF6

Which one of the following is a mineral of iron?

1. Malachite
2. Cassiterite
3. Pyrolusite
4. Magnetite

The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.

1. Fe2O3(s) + 3CO(g) 2Fe(l) + 3CO2(g)
2. CaCO3(s) CaO(s) + CO2(g)
3. CaO(s) + SiO2(s) CaSiO3(s)
4. 2C(s) + O2(g) 2CO(g)

Which of the following elements is present as the impurity to the maximum extent in pig iron?

1. Manganese
2. Carbon
3. Silicon
4. Phosphorus

Which of the following pairs of metals is purified by van Arkel method?

1. Ga and In
2. Zr and Ti
3. Ag and Au
4. Ni and Fe

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

1. Galena
2. Copper pyrite
3. Sphalerite
4. Argentite