Tag: refining of metals

Questions Related to refining of metals

When alloy of silver and lead is rich in silver:

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. Cupellation process is used

  2. Parke's method is used

  3. Pattinson's method is used

  4. Any of the above methods can be used

Show answer
Correct Option: A
Explanation:

When alloy of silver and lead is rich in silver, cupellation process is used.
The silver metal can be obtained in when alloy of silver and lead is rich in lead is:
i) Parke's process
ii) Pattinson's process

Softening of lead means:

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. Melting pure lead at high temperature

  2. Removal of impurities, except silver, present in commercial lead

  3. Formation of lead alloy

  4. Formation of 100% pure lead

Show answer
Correct Option: B
Explanation:

We know the melting point of pure lead is very high. Softening of lead means removal of metallic impurities, except silver, present in the commercial lead. 


B  is the correct answer

Tin is not refined by:

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. Liquidation

  2. Zone refining

  3. Poling

  4. None of the above

Show answer
Correct Option: B
Explanation:
Poling is a [metallurgical] method employed in the purification of copper which contains copper oxide as an impurity and also in the purification of tin ("Sn") which contains tin oxide (stannic oxide or "$SnO _2$") as an impurity. It was the use of these greenwood poles gave rise to the term "poling."

Liquidation is suitable for metals with low melting points for example, tin. In this process, we heat the impure metal and then we let it flow on a sloped surface. The impurities will remain behind and the pure metal will collect at the bottom of the slope.


Zone refining is a special method we use to purify metals. It was the invention of William Pfann. It purifies metals to a very high degree. A rod of impure metal is placed in a container which we fill with inert gas. Then we place a circular heater around the rod at the top.

The melting point of tin is low. So zone refining is not suitable for Tin.

Hence, option B is correct.

When alloy of silver and lead is rich in silver :

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. CupelIation process is used

  2. Parke's method is used

  3. Bett's method is used

  4. All of the above method

Show answer
Correct Option: A
Explanation:
Cupellation: Pb impurities present in Ag are removed by this method. The impure metal is heated in a cupel or oval shaped crucible made of bone ash or cement and blast of air is passed over the molten mass. The impurities get oxidised and removed with the blast of air.

Refining of tin can be done by :

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. cupellation

  2. liquation

  3. poling

  4. electrorefining

Show answer
Correct Option: B,C,D
Explanation:
Poling is a method employed in the purification of copper which contains copper oxide as an impurity and also in the purification of tin ("Sn") which contains tin oxide (stannic oxide or "SnO2") as an impurity. It was the use of these greenwood poles gave rise to the term "poling."

Liquation is suitable for metals with low melting points, for example, tin. In this process, we heat the impure metal and then we let it flow on a sloped surface. The impurities will remain behind and the pure metal will collect at the bottom of the slope.

Electrorefining, producing pure tin from waste materials in cheap acid electrolytes can be effectively operated with parameters set to provide for the stability of the solution and high current efficiencies and the use of the periodical current reversal (PCR) technique.

Cupellation is a refining process in metallurgy where ores or alloyed metals are treated under very high temperatures and have controlled operations to separate noble metals, like gold and silver, from base metals, like lead, copper, zinc, arsenic, antimony, or bismuth, present in the ore.

Cupellation is used for purifying of metal under high temperature. so it is not suitable for tin(low melting point metal).

Extraction of metal from the ore cassiterite involves

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. carbon reduction of an oxide ore

  2. self- reduction of an sulphide ore

  3. removal of iron impurity

  4. both A and C

Show answer
Correct Option: D
Explanation:

Tin is obtained by reducing the ore cassiterite with coal in a reverberatory furnace; limestone is added to produce a slag with impurities, which can be removed.

$SnO _2  +  2C \longrightarrow Sn + 2 CO$.

Crude tin so obtained is contaminated with iron, lead, and other metals. It is, therefore, remelted on an inclined furnace. The process is called liquation. The easily fusible tin metals away and the less fusible impurities are left behind. Molten tin is finally stirred with green poles of wood in contact with air. In this process, any remaining metal impurities are oxidized forming a scum, which rises to the surface and is removed. This process is called polling.

Which are correctly matched?

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. Poling-refining of copper

  2. Cupellation- refining of silver

  3. Smelting-An oxidation process

  4. Roasting-An oxidation process

Show answer
Correct Option: A,B,D
Explanation:

A) Poling is a method employed in the purification of copper which contains cuprous oxide as an impurity.correct.
B) Cupellation is a refining process in metallurgy, where ores or alloyed metals are treated under high temperatures and controlled operations to separate gold and silver, from lead, copper, zinc, arsenic, antimony or bismuth.correct.
C) The process of extracting a metal from its oxide is known as 'smelting'. Most smelting processes involve direct reduction of the ore by carbon to metal and carbon dioxide. The production of primary aluminium is a good example of such a process. Its not oxidation.wrong
D) Roasting is a step of the processing of certain ores More specifically, roasting is a metallurgical process involving gassolid reactions at elevated temperatures with the goal of purifying the metal component(s). During roasting, the sulfide is converted to an oxide, and sulfur is released as sulfurdioxide, a gas.$2Cu _2S + 3O _2\rightarrow  2 Cu _2O + 2 SO _2$.correct.
options A,B & D are correct.

In Poling process, Hydrocarbon gases escaping from the poles act as _____ agents.

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. reducing

  2. oxidation

  3. both

  4. none

Show answer
Correct Option: A
Explanation:

Poling is a process in which the impure metal containing oxide as impurities is purified. It is melted and stirred with green poles of wood. Hydrocarbon gases escaping from the poles act as reducing agents and reduce the oxide impurities e.g., impurity of Cu$ _2$O which is reduced to metallic copper by poling.
$Cu _2O + CO \rightarrow 2Cu + CO _2 \uparrow$
$Cu _2O + H _2 \rightarrow 2Cu + H _2O$

In polling, wood gas is responsible for the removal of volatile impurities.

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

True. Polling is used for converting Copper Oxide $(Cu _2O)$ to Copper $(Cu)$. When ore is heated with wood poles, the poles release charcoal, shoot and gas. The gas released reduces $CuO$ to $Cu$. So the gas takes away impurities. 

Which of the following methods is used to remove lead present in silver ?

chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

  1. Cupellation

  2. Distillation

  3. Poling

  4. Lavigation

Show answer
Correct Option: A
Explanation:

Cupellation is a process of separation of gold or silver from impurities by melting the impure metal in a cupel (a flat porous dish made of refractory or high-temperature resistant material  ) and then directing a blast of hot air on it in a special furnace. The impurities, including lead,copper, tin, and other unwanted metals, are oxidized and partly vaporized and partly absorbed into the pores of the cupel.