Railway Science (Chemistry-Metallurgy)

Total Questions: 13

11. n the froth flotation method, Ore powder is placed in a tank filled with a mixture of _________. [RRB Group D 12/11/2018 (Evening)]

Correct Answer: (b) Water and Pine oil
Solution:

Froth flotation is an important concentration process that can be used to selectively separate hydrophobic materials from hydrophilic waste gangue. This method is commonly used for the concentration of sulfide ores, such as copper, lead, and zinc ores, among others.

12. Heating of ores in the absence of oxygen is called: [RRB Group D 06/12/2018 (Morning)]

Correct Answer: (b) Calcination
Solution:

The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination. The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting. Oxygen reacts with metals to form oxides. Oxidation of metals is known corrosion for example rusting of iron.

13. By which of the following processes are metals of high reactivity extracted from purified molten ore? [RRB ALP Tier - I (09/08/2018) Morning]

Correct Answer: (c) Electrolysis
Solution:

Metals of high reactivity such as Magnesium (Mg), Calcium (Ca) and Sodium (Na) are extracted from purified molten ore by the Electrolysis process. In the Electrolysis process, electric current is passed through the molten state of metal ores.
In this process metals are deposited over the cathode. Calcination is mostly used in the oxidation of carbonates. Roasting is a method that is used for converting sulphide ores.
Example - 2ZnS (Zinc sulfide) + 3O₂ → 2ZnO (Zinc oxide) + 2SO₂(Sulfur dioxide). 3 types of Sulphides: organic sulphides (thioethers), inorganic sulphides and phosphine Sulphides.