Electrometallurgy

Q.

During electroplating of nickel on a substance, AQUEOUS NiSO_{4 is taken as electrolyte} and current is passed . According to our book, the Ni²⁺ ions migrate to the cathode and take 2 electrons forming Ni metal on the cathode . Also, the Ni anode get decomposed as Ni²⁺ ions.

But, at the cathode, H+ ions must go and undergo reduction by gaining ions because H+ is lower than Ni2+ in the electrochemical series and H+ can gain electrons more readily because of its small atomic size. Then why Ni+2 ions go to cathode and undergo reduction?

Or should MOLTEN NiSO4 be taken as an electrolyte for electroplating of Nickel on a metal so that there are no H⁺ ions in the electrolyte and only Ni²⁺ ions go at cathode and get deposited on the metal ?

Q.

Explain with reasons:

(a) In the electrolytic reduction of alumina, the graphite anode is gradually consumed.

or

Why the anode has to be replaced in this process?

(b) Roasting is carried out on sulphide ores and not on carbonate ores.

(c) Carbon can reduce lead oxide but not aluminium oxide.

(d) Electrolytic reduction is done to obtain aluminium?

(e) Why 'the food containing iron salts' should not be cooked in aluminium utensils?

Q. Explain electrolytic reduction of alumina with the help of diagram.

Q.

Select the correct option about the oxidizing agent.

1. Non-metals are mostly oxidizing agents

2. Metals are mostly oxidizing agents

3. oxidizing agents decrease in oxidation state

4. Oxidizing agents are mostly transition metals

Q.

Name a metal which reacts with very dilute HNO_{​​​​3}​​​ to evolve hydrogen

Q.

To extract potassium $K$ from Karnalite ($KCl.MgC{l}_2.6H_{2}O$), the reduction process used is ___.

1. smelting

2. electrolysis

3. leaching

4. pyro refining

Q.

(a) The following is an extract from 'Metals in the service of Man, Alexander and Street/ Pelican 1976':
'Alumina (aluminium oxide) has a very high melting point of over 2000°C so that it cannot readily be liquefied. However, conversion of alumina to aluminium and oxygen, by electrolysis, can occur when it is dissolved in some other substance'.
(i) Which solution is used to react with bauxite as a first step in obtaining pure aluminium oxide?
(ii) The aluminium oxide for the electrolysis of aluminium is obtained by heating aluminium hydroxide. Write the equation for this reaction.
(iii) Name the element which serve both as the anode and the cathode in the extraction of aluminium.
(iv) Write the equation for the reaction that occurs at the cathode during the extraction of aluminium by electrolysis.
(v) Give the equation for the reaction which occurs at the anode when aluminium is purified by electrolysis.

Q. In the Hall's process for extraction of aluminium,
(a) give the formula and purpose of fluorspar and cryolite.
(b) state the location of cathode and anode and explain what occurs at each electrode.

Q.

The cathode used to extract pure metal from the ore corundum by electrorefining is ________.

1. Inert graphite

2. Pure aluminium

3. pure iron

4. pure copper

Q.

Why is electrolytic reduction done to obtain aluminium ?

Q.

During electrolytic reduction of molten Alumina, Aluminium metal is obtained at

1. Carbon anode

2. Carbon cathode

3. Aluminium anode

4. Aluminium cathode

Q.

Identify the reaction that takes place at the cathode during electrolytic refining of the extracted metal M.​

1. $M^{n+}+{\mathrm{ne}}^{-}\to M$
2. $M\to M^{n+}+{\mathrm{ne}}^{-}$

Q.

Which of the following metals refined/extracted by electrometallurgy?

1. Mercury (Hg)

2. Iron (Fe)

3. Aluminium (Al)

4. Lead (Pb)

Q. Assertion :Magnesium is extracted by electrolytic reduction.
Reason: All metals are extracted by electrolytic reduction.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q.

Match the items in Column 1 with items in Column 2.

$\begin{array}{cc}\text{Column 1}& \text{Column 2}\\ \text{i) Anode-mud}& \text{a) protects objects from corrosion}\\ \text{ii) Electroplating}& \text{b) purification of metals}\\ \text{iii) Electrorefining}& \text{c) Au, Ag, Pt}\end{array}$

1. i$\to$a, ii$\to$c, iii$\to$b

2. i$\to$b, ii$\to$a, iii$\to$c

3. i$\to$a, ii$\to$b, iii$\to$c

4. i$\to$c, ii$\to$a, iii$\to$b

Q. Which method would you suggest for the extraction of highly reactive metals from their concentrated ores?
[1 Mark]

Q.

A scrap metal dealer gets a huge consignment of crude metallic Lead. For a profitable deal he needs to refine the metal using electrolysis. Which one of the following is a good choice for an electrolyte?

1. All of the above

2. PbI₂

3. PbSiF₆

4. PbCl₂

Q. Sameer wants to electroplate his key chain with nickel to prevent rusting. For this electroplating give the reaction at the cathode.

1. $N{i}^{2+}+2e^{-}\to Ni$
2. $N{i}^{+}+1e^{-}\to Ni$
   
3. $N{i}^{3+}+3e^{-}\to Ni$
4. None of these

Q. The metal refined-electolytically is:

1. $Al$
2. $Na$
3. $Cu$
4. $Fe$

Q. Select the correct answer from the choices a, b, c and d which are given.
Write only the letter corresponding to the correct answer.
(i) A compound which liberates reddish brown gas around the anode during the electrolysis in its molten state is:
(a) Sodium chloride
(b) Copper (II) oxide
(c) Copper (II) sulphate
(d) Lead (II) bromide

(ii) During ionization metals lose electrons, this change can be called:
(a) Oxidation
(b) Reduction
(c) Redox
(d) Displacement

Q.

The cathode used to extract pure metal from the ore corundum by electrorefining is ___

1. Inert graphite

2. pure iron

3. Pure aluminium

4. pure copper

Q. Chromium is obtained by reducing purified chromite ore with :

1. Red hot coke
2. Aluminium powder
3. Gaseous hydrogen
4. Carbon monoxide

Q. In the Castner process for the extraction of sodium, the anode is made of _______ metal.

1. Copper
2. Nickel
3. Carbon
4. Sodium

Q. Give reason for the following:
Aluminum is extracted from its oxide by electrolytic reduction and not by conventional reduction agents.

Q. Name the product formed when $Zn$ reacts with $NaOH$.

1. $Zn(OH{)}_2$
2. $N{a}_{2}Zn{O}_2$
3. $H_2$
4. $H_{2}O$

Q. Give scientific reasons
Anodes need to be replaced from time to time during the electrolysis of alumina.

Q. Find out the process C in the given flowchart:

1. Electrolysis
2. Reduction
3. Roasting
4. Smelting

Q. In the electrolytic refining of silver, the anode mud obtained contains :

1. $Zn,Ag,$ and $Au$
2. $Zu,Cu,Ag,$ and $Au$
3. $Au$
4. $Cu,Ag,$ and $Au$

Q.

For the extraction of aluminium answer the following

c. What is used as a cathode?

Q. An electroplating factory should dispose-off their waste :

1. in the nearby field
2. according to guidelines of local authority
3. in the nearby river
4. in the nearby garbage