General Principles And Processes Of Isolation Of Elements

(i) Hall's process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide in molten cryolite and electrolysing the molten salt bath

(ii) Hoope's process or electrolytic refining is used to refine the obtained aluminium metal which is not pure.

(iii) Mond's process is used to refine nickel.

(iv) Liquation process is used to refine a metal with low melting point like tin, bismuth, lead, mercurv etc.

Limestone is used as a flux in the extraction of iron because it decomposes in hot furnace to form calcium oxide and carbon dioxide. The formed calcium oxide actually acts as flux and combined with silica to form fusible calcium silicate slag

Step 1: Understanding volume strength of hydrogen peroxide.
The volume strength of hydrogen peroxide refers to the volume of oxygen gas that 1 liter of the solution can produce when decomposed. A 20-volume solution of H O means that 1 liter of the solution will produce 20 liters of oxygen gas. From the molar mass of hydrogen peroxide (34 g/mol), the strength can be calculated. The correct strength of a 20-volume solution is 60.71 g/L.
Step 2: Analyzing the options.
(A) 60.71 g/L: This is the correct answer, as the volume strength and mass concentration are related as described.
(B) 6.8 g/L: This is incorrect, as it is much too low for a 20-volume solution.
(C) 68 g/L: This is also incorrect, as it is too high for the given solution strength.
(D) 6.071 g/L: This is incorrect, as it does not match the correct concentration for a 20-volume solution.
Step 3: Conclusion.
The correct answer is (A) 60.71 g/L.

Step 1: Understanding the effect of non-volatile solutes.
When a non-volatile solute is added to a solvent, it lowers the vapour pressure of the solution compared to the pure solvent. This phenomenon is explained by Raoult’s law. Non-volatile solutes do not evaporate, so they reduce the number of solvent molecules at the surface, which decreases the vapour pressure.
Step 2: Analyzing the options.
(A) Vapour pressure of a solution containing a non-volatile solute is always less than vapour pressure of pure solvent: This is correct, as explained by Raoult’s law.
(B) Liquids having greater intermolecular forces have lower boiling points: This is incorrect, as stronger intermolecular forces usually lead to higher boiling points.
(C) Boiling point of pure solvent is always greater than boiling point of its solution containing a non-volatile solute: This is incorrect; the boiling point of a solution is higher than that of the pure solvent (boiling point elevation).
(D) Vapour pressure of a solution containing a non-volatile solute is always greater than vapour pressure of pure solvent: This is incorrect. The presence of a non-volatile solute lowers the vapour pressure.
Step 3: Conclusion.
The correct statement is (A).

Step 1: Applying the law of combining volumes.
According to the law of combining volumes, the volumes of reacting gases are in simple whole number ratios. Here, 8 volumes of hydrogen (H ) react with 4 volumes of oxygen (O ) to form 8 volumes of water vapor (H O).
Step 2: Molar relationship.
From the balanced chemical equation: The molar ratio of hydrogen to water is 2:2, so the volume ratio is 1:1. Thus, 8 volumes of H will produce 8 volumes of H O.
Step 3: Calculating the mass of water produced.
The molar mass of water (H O) is 18 g/mol. Since the volume of hydrogen is 8 volumes, this corresponds to 8 moles of water. Therefore, the mass of water produced is: Step 4: Conclusion.
The correct answer is (D) 144 g.