Question:

In liquation process used for tin (Sn), the metal

Updated On: Dec 29, 2025
  • is reacted with acid
  • is dissolved in water
  • is brought to molten form which is made to flow on a slope
  • is fused with NaOH
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The Correct Option is C

Solution and Explanation

The liquation process for tin (Sn) is a metallurgical method used to separate tin from other impurities or less fusible impurities in the metal. The process leverages the difference in the melting points of tin and its impurities.

  1. Basic Principle: The process relies on the fact that tin has a lower melting point (approximately 232°C) compared to its impurities.
  2. Procedure: The tin ore or tin-containing scrap is gently heated to a temperature slightly above tin's melting point. This temperature allows tin to melt while most of the impurities remain solid.
  3. Flow on a Slope: The molten tin is allowed to flow down a sloped surface or inclined plane. The liquid tin runs down, while the solid impurities remain on the surface.

Justification of Correct Option:

The correct option is "is brought to molten form which is made to flow on a slope". This describes the liquation process accurately, as the tin melts and flows away from its solid impurities.

Reasoning:

  • Option: "is reacted with acid" - This is incorrect because the liquation process involves melting, not chemical reactions.
  • Option: "is dissolved in water" - This is incorrect because tin is not soluble in water, and the process does not involve dissolution.
  • Option: "is fused with NaOH" - This is incorrect because fusion with NaOH is not part of the liquation process. This would involve a chemical reaction, not simple melting and separation.

In summary, the liquation process used in tin metallurgy involves bringing the metal to a molten form and utilizing a sloped surface to separate tin from its less fusible impurities.

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Concepts Used:

Liquefaction of Gases

Liquefaction of gases

Liquefaction of gases is the physical conversion of a gas into a liquid state. When pressure on a gas is increased, its molecules closer together, and its temperature is reduced, which removes enough energy to make it change from the gaseous to the liquid state. Ammonia gas can be liquefied by applying high pressure and lowering the temperature. Any gas can be liquefied when the gas has been exposed to the high pressures and low temperatures. The pressure that has to be applied as well as the temperature depends on the molecular forces of the gas molecules.

Critical Pressure

Critical Pressure of a substance is the pressure that corresponds to the critical point of the substance. 

“The minimum pressure that must be applied to liquefy a gas at its critical temperature is called critical pressure.” The critical pressure of a substance is also denoted as PC.

The relation between critical pressure and Van der Waals equation is given as:

PC= a/ 27b2

Critical Temperature (TC)

The characteristic temperature of a gas above which the gas cannot be liquefied by applying pressure is called critical temperature. The relation between critical temperature and Van der Waals equation can be given as

 TC= 8a/ 27RB

Critical Volume(VC) 

The volume occupied by 1 Mole of gas at its critical pressure and critical temperature is called the Critical Volume. The relation between critical volume and Van der Waals constants is 

Vc = 3b

Critical Pressure: Liquefaction of Gases

The phenomenon of converting gas into liquid by lowering the temperature or by increasing the pressure or both is known as liquefaction of gases.

Gases like CO2, HCl, NH3, Cl2, and SO2 get liquefied at room temperature when sufficiently high pressure is applied. Such gases are called temporary gases.

Gases like He, H2, N2, O2, CO and CH4 don't liquefy at room temperature no matter how much high pressure may be applied. These gases are called permanent gases”.

Critical Pressure: Triple Point 

Every matter has three common states which are solid, liquid, and gas. The physical state of matter is due to two primary factors, temperature, and pressure. Each substance has a different phase boundary, and by adjusting the temperature-pressure combinations, the phase boundary of any substance can be marked. 

Some substances can exist in all three states of matter. The point at which a substance can exist in all three states is called the Triple Point. 

Critical Pressure: Triple Point of Water

Water exists in three states; solid(ice), liquid(water), gas(water vapour). The triple point of water is defined as the temperature and pressure at which liquid water, solid ice and water vapour can coexist in a stable equilibrium. 

The thermal stable equilibrium is at 293.1600 K and partial vapour pressure of 611.657 Pascals. Even if the total pressure of a system is above the triple point of water, provided that the partial pressure of the water vapour is 611.657 Pa, then the system can still be brought to the triple point of water. 

Critical Pressure of Fluid

The critical pressure of a fluid can be defined as the vapour pressure of the fluid at its critical temperature. Above the critical point, distinct gas and liquid phases do not exist. While attaing the critical temperature of a substance, the properties of the gases and liquid phases are almost similar, resulting in only one phase.