All Free Chemistry MCQs with Answers

• A. NaOH
• B. CuSO4
• C. NaCN
• D. CaO

Explanation: Option C is correct. NaCN is used as a depressant in the concentration of galena by froth flotation method.

• A. reduction
• B. oxidation
• C. reduction followed by oxidation
• D. oxidation followed by reduction

Explanation: Option D is correct. The chemical processes in the production of steel from hematite ore involve oxidation followed by reduction.

• A. Tin plating
• B. Conversion of white tin to grey tin
• C. Emission of sound while bending a tin plate
• D. Conversion of stannous salts to stannic salts.

Explanation: Option B is correct. Tin plague is the conversion of white tin to grey tin. White tin is the stable form of tin at room temperature.

• A. The metal present in the mineral is costly
• B. A metal can be extracted from it
• C. A metal can be extracted profitably from it
• D. A metal cannot be extracted from it.

Explanation: Option C is correct. A mineral is termed an ore if a metal can be extracted profitably from it.

• A. There is special arrangement in the cell to keep the layers separate.
• B. The three layers have different densities.
• C. The upper layer is kept attracted by the cathode and the lower layer is kept attracted by the anode.
• D. Both B and C

Explanation: Option D is correct. The three layers have different densities. In the Hoope's process for refining of aluminium, the fused materials form…

• A. Anglesite
• B. Galena
• C. Cerussite
• D. Azurite

Explanation: Option B is correct. Galena is the major ore of lead. It is a lead sulfide mineral with the chemical formula PbS.

• A. In the presence of NaCl.
• B. In the presence of fluorite.
• C. In the presence of cryolite which forms a melt with lower melting temperature.
• D. In the presence of cryolite which forms a melt with higher melting temperature.

Explanation: Option C is correct. The electrolytic reduction of alumina to aluminum by the Hall-Heroult process is indeed carried out in the presence…

• A. Poisonous compound present in petrol
• B. Antiknock compound
• C. Component of ethyl fluid
• D. All of these

Explanation: Option D is correct. Tetraethyl lead is a poisonous compound that was once used as an antiknock compound in petrol.

• A. Calcination
• B. Froth floatation
• C. Leaching
• D. Both (b) and (c)

Explanation: Option D is correct. Froth floatation and Leaching are both concentration techniques used in the separation of metals.

• A. Oxidizing nature
• B. Very strong affinity for oxygen
• C. High boiling point
• D. Both B and C

Explanation: Option B is correct. The property of aluminium that is used for the extraction of metals from their ores is its high affinity for oxygen.

• A. A protective coating of PbCl2 is formed on the metal
• B. Pb is less electropositive than H2
• C. PbO film is formed which resists chemical attack by the acid.
• D. Both A and C

Explanation: The correct answer is Option D. Lead is not affected by dilute HCl in the cold because both a protective coating of PbCl2 and a thin layer…

• A. Graphite
• B. CaO
• C. SiO2
• D. MgO

Explanation: Silicon dioxide (SiO2) is used as a neutral refractory material in furnaces due to its high resistance to heat and chemicals.

• A. Flux
• B. Catalyst
• C. Ore
• D. Slag

Explanation: Flux combines with gangue to form a low melting and fusible substance called slag.

• A. It reacts with NaOH and glucose to give Cu2O
• B. It reacts with KCl to give Cu2Cl2
• C. It gives CuO on strong heating
• D. It reacts with KI to give I2

Explanation: The correct answer is that the statement about copper sulfate reacting with KI to produce I2 is inaccurate.

• A. Carbonates
• B. Sulphides
• C. Oxides
• D. Phosphates

Explanation: The correct answer is Option B: Sulphides. In the floatation process, the ore particles should have aerofillic in preference to gangue…

• A. Ag
• B. Mg and Al
• C. Ca
• D. All

Explanation: Magnesium and aluminium can be obtained by the electrolytic reduction of their ores respectively, as they are highly reactive metals with…

• A. Horn silver
• B. Calcite
• C. Hamatite
• D. Magnesite

Explanation: Haematite is the correct answer because it has magnetic properties, making it suitable for separation using magnetic separation…

• A. Lime stone
• B. Magnesia
• C. Silica
• D. Coke

Explanation: In the smelting of copper ore SiO2 is used as a flux as it forms FeSiO2 as fusible slag.

• A. Zone refining
• B. Poling
• C. Electrolytic refining
• D. Cupelling

Explanation: Electrolytic refining is the most effective method for obtaining high purity copper, with a purity level of 99.99%.

• A. Electrolysis of fused MgCl2
• B. Reducing calcined dolomite with ferrosilicon at high temperature under pressure.
• C. Both are correct
• D. None is correct

Explanation: In the Pidgeon process, magnesium is produced by reducing calcined dolomite with ferrosilicon at high temperature under pressure.