Test: Ellingham's Diagram & Its Applications: Thermodynamic Principles of Metallurgy
25 Questions MCQ Test Chemistry Class 12 | Test: Ellingham's Diagram & Its Applications: Thermodynamic Principles of Metallurgy
Only One Option Correct Type
Direction : This section contains 9 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE is correct.
Q.
Ellingham diagram represents a graph of
Eilingham diagram represents a graph of ΔG° vs T.
ΔG° vsT plot in the Ellingham diagram slopes down for the reaction.
In the case of carbon reacting with dioxygen.
two volumes of CO for every one volume of dioxygen used. Thus, ΔS is positive and hence ΔG becomes increasilngly negative as temperature increases. Consequently the line on Eilingham diagram slope downwards.
The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.
A slag is an easily fusible material which is formed when gangue still present in the roasted or the calcined ore combines with the flux. For example, in the metallurgy of iron, CaO (flux) combines with silica gangue to form easily fusible calcium silicate (CaSiO3) slag.
CaO + SiO2 → CaSiO3 (slag)
Which metal has a greater tendency to form metal oxide?
Because the change in free energy i.e. ΔG is highly negative for this reaction,
The main reaction occurring in blast furnace during the extraction of iron from haematite is
3Fe2O3 + CO → 2Fe3O4 + CO2
Fe3O4 + CO → 3FeO + CO2
FeO + CO → Fe + CO2
Consider the following reactions at 10000° C,
Then choose the correct statement from the following.
Because the ΔG° of the formation of CO is more negative than that of ZnO at 10000°C.
According to Ellingham diagrams the oxidation reaction of carbon and carbon monoxide may be used to reduce which one of the following oxides at the lowest temperature?
Because ΔG° for reductions of rest three oxides [Al2O3, ZnO and MgO] are less negative than that of Cu2O at lower temperature.
The minimum voltage required to electrolyse alumina in the Hall-Heroult process is [Given, 
(Al2O3) = - 1520 kJ/mol and 
(CO2) = 394 k J/mol]
In Hall - Heroult process the following reactions occur
Based on the given information (CaO) = - 604.2 kJ/mol and (Al2O3) = - 1582 kJ/mol, which of the following is feasible?
3Ca + Al2O3 → 2AI + 3CaO
ΔG°= 3 x(CaO) -(Al2O3)
= 3 x (-604.2)-(-1582)
= -1812 + 1582 = -230 kJ
ΔG° is negative. Hence, this reaction is feasible.
One or More than One Options Correct Type
Direction : This section contains 5 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.
Q.
For the metallurgical process of which of the calcined ore can be reduced by carbon?
Calcined ore of haematite (Fe2O3) and zincite (ZnO) can be reduced by carbon.
For which oxide formation ΔG° is more negative than Gr2O3?
According to Eilingham diagram, 
for Al2O3 and MgO is more negative than Cr2O3.
In the extraction of iron from haematite in blast furnace reducing agent
The correct answer is option
Carbon monoxide is the actual reducing agent of haematite in blast furnace.
C + O2 → CO2↑
CO2 + C → 2CO↑
Fe2O3 + CO → 2FeO + CO2↑
FeO + CO → Fe + CO2↑
Based on the given information, 
(CaO) = -604.2 kJ/mol and (Al2O3) = - 1582 kJ/mol, which o f the following is correct?
3CaO + 2AI → Al2O3 + 3Ca
ΔG °= (Al2O3) - 3(CaO)
= - 1582 - 3 (-604)
= -1582 + 1812 = +230 kJ
ΔG° is positive. Hence this reaction is not spontaneous.
Consider the Ellingham diagram given below. Which metal(s) in the diagram can be extracted at 1100 K using coke as a reducing agent?
In the extraction of iron, at low temperature CO is effective and at high temperature carbon is more effective.
Comprehension Type
Direction : This section contains a paragraph, describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer among the four given options (a), (b), (c) and (d).
Passage
Q.
To make the reduction ZnO+ C → Zn + CO spontaneous, temperature should be
The temperature should be above the intersecting temperature.
Passage
Q.
At 1100°C, which reaction is spontaneous to a maximum extent ?
At 1100° C the ΔG° for
ZnO + Mg → Zn + MgO, is more negative then other three reactions.
Matching List Type
Direction : Choices for the correct combination of elements from Column I and Column II are given as options (a), (b), (c) and (d), out of which one is correct.
Q.
Match the Column I with Column II and mark the correct option from the codes given below.
(i) → (q), (ii) → (r), (iii) → (s), (iv) → (p)
Match the Column I with Column II and mark the correct option from the codes given below.
(i) → (r,t), (ii) → (p), (iii) → (s), (iv) → (q)
One Integer Value Correct Type
Direction : This section contains 5 questions. When worked out will result in an integer from 0 to 9 (both inclusive).
Q.
In the Gibbs equation at equilibrium the value of ΔG is
ΔG = ΔH-T&S
At eqbm. (ΔG = 0)
0 = ΔH - 7ΔS ⇒ ΔH = TΔS
The reaction 3CaO + 2AI → Al2O3 + 3Ca is non-spontaneous. The number of electrons involved are
3CaO + 2Al Al2O3 + 3Ca
At anode: 2Al(s) 2Al3+ + 6e-
At cathode: 3Ca2+ + 6e- 3Ca(s)
Hence, number of e- involved = 6
The given reaction 2AI + Cr2O3 → Al2O3 + 2Cr is spontaneous. The number of electrons involved are
6 electrons from 2 Al-atoms participate.
Among PbO, ZnO, CaO, Al2O3, SnO2, Cr2O3, WO3, HgO the oxides reduced by carbon are
PbO, ZnO and SnO2 are reduced by carbon.
Cu2+ + Fe → Cu + Fe2+ for this reaction to calculate ΔG° the formula ΔG° = - nFE° is used. Here, value of n is
ΔG°= -nFE°, n = number of electrons involved
Statement Type
Direction : This section is based on Statement I and Statement II. Select the correct answer from the codes given below.
Q.
Statement I : Carbon is good reducing agent for sulphides.
Statement II : Carbon is poor reducing agent for iron oxide.
Carbon is a good reducing agent for oxides, it is a poor reducing agent for sulphides. The reason why carbon reduces so many oxides at elevated temperature is that the ΔG°/T line for CO has a negative slope. There is no compound as analogous to CO with a steep negative ΔG°/T line. Thus sulphides are normally roasted in air to form oxides before reducing with carbon
2 MS + 3O2 → 2MO + 2SO2
Statement I : Carbon can reduce Fe2O3 to Fe at a temperature below 983 K.
Statement II : Iron has higher affinity toward oxygen than carbon.
Below 983 K iron having higher affinity towards oxygen than carbon, carbon cannot reduce Fe2O3 to Fe.
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