12th Chemistry - Book Back Answers - Unit 1 Metallurgy - English Medium Guides

  

 

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Tamil Nadu Board 12th Standard Chemistry - Unit 1: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 1 from the Tamil Nadu State Board 12th Standard Chemistry textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Unit 1 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 12 students! Prepare well and aim for top scores. Thank you!

I. Multiple Choice Questions

1. Bauxite has the composition

a) Al₂O₃

b) Al₂O₃.nH_₂O

c) Fe₂O₃.2H₂O

d) None of these

Answer Key:

b) Al₂O₃.nH_₂O  

2. Roasting of sulphide ore gives the gas (A).(A) is a colourless gas. Aqueous solution of (A) is acidic. The gas (A) is

a) CO₂

b) SO₃

c) SO₂

d) H₂S

Answer Key:

c) SO₂ 

  

3. Which one of the following reaction represents calcinations?

a) 2Zn + O₂→2ZnO

b) 2ZnS + 3O₂→2ZnO + 2SO₂

c) MgCO₃→MgO + CO₂

d) Both (a) and (c)

Answer Key:

c) MgCO₃→MgO + CO₂ 

  

4. The metal oxide which cannot be reduced to metal by carbon is

a) PbO

b) Al₂O₃

c) ZnO

d) FeO

Answer Key:

b) Al₂O₃ 

  

5. Which of the metal is extracted by Hall-Heroult process?

a) Al

b) Ni

c) Cu

d) Zn

Answer Key:

a) Al 

  

6. Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

a) $\mathbf{△}{\mathbf{G}}_{\mathbf{f}}\mathbf{°}$, of sulphide is greater than those for CS₂, and H₂S.

b) $\mathbf{△}{\mathbf{G}}_{\mathbf{r}}°$, is negative for roasting of sulphide ore to oxide

c) Roasting of the sulphide to its oxide is thermodynamically feasible.

d) Carbon and hydrogen are suitable reducing agents for metal sulphides.

Answer Key:

b) $\mathbf{△}{\mathbf{G}}_{\mathbf{r}}°$, is negative for roasting of sulphide ore to oxide 

  

7. Match items in column - I with the items of column - II and assign the correct code.

Column-I		Column-II
A	Cyanide process	(i)	Ultrapure Ge
B	Froth floatation process	(ii)	Dressing of ZnS
C	Electrolytic reduction	(iii)	Extraction of Al
D	Zone refining	(iv)	Extraction of Au
		(v)	Purification of Ni

	A	B	C	D
(a)	(i)	(ii)	(iii)	(iv)
(b)	(iii)	(iv)	(v)	(i)
(c)	(iv)	(ii)	(iii)	(i)
(d)	(ii)	(iii)	(i)	(v)

Answer Key:

c) A-iv , B-ii , C-iii , D-i

 

8. Wolframite ore is separated from tinstone by the process of

a) Smelting

b) Calcination

c) Roasting

d) Electromagnetic separation

Answer Key:

d) Electromagnetic separation 

  

9. Which one of the following is not feasible

a) Zn(s) + Cu²⁺(aq) → Cu(s) + Zn²⁺⁽aq)

b) Cu(s) + Zn²⁺(aq)→ Zn(s) + Cu²⁺(aq)

c) Cu(s) + 2Ag⁺(aq) → 2Ag(s) + Cu²⁺(aq)

d) Fe(s) + Cu²⁺(aq) → Cu(s) + Fe²⁺(aq)

Answer Key:

b) Cu(s) + Zn²⁺(aq)→ Zn(s) + Cu²⁺(aq) 

  

10. Electrochemical process is used to extract

a) Iron

b) Lead

c) Sodium

d) silver

Answer Key:

c) Sodium 

  

11. Flux is a substance which is used to convert

a) Mineral into silicate

b) Infusible impurities to soluble impurities

c) Soluble impurities to infusible impurities

d) All of these

Answer Key:

b) Infusible impurities to soluble impurities 

  

12. Which one of the following ores is best concentrated by froth - floatation method?

a) Magnetite

b) Haematite

c) Galena

d) Cassiterite

Answer Key:

c) Galena 

  

13. In the extraction of aluminium from alumina by electrolysis, cryolite is added to

a) Lower the melting point of alumina

b) Remove impurities from alumina

c) Decrease the electrical conductivity

d) Increase the rate of reduction

Answer Key:

a) Lower the melting point of alumina 

  

14. Zinc is obtained from ZnO by

a) Carbon reduction

b) Reduction using silver

c) Electrochemical process

d) Acid leaching

Answer Key:

a) Carbon reduction 

  

15. Extraction of gold and silver involves leaching with cyanide ion. silver is later recovered by

a) Distillation

b) Zone refining

c) Displacement with zinc

d) liquation

Answer Key:

c) Displacement with zinc 

  

16. Considering Ellingham diagram, which of the following metals can be used to reduce alumina?

a) Fe

b) Cu

c) Mg

d) Zn

Answer Key:

c) Mg 

  

17. The following set of reactions are used in refining Zirconium

Zr (impure) + $\mathbf{2}{\mathbf{I}}_{\mathbf{2}}\stackrel{\mathbf{523}\mathbf{ }\mathbf{k}}{\mathbf{\to }}\mathbf{Z}\mathbf{r}{\mathbf{I}}_{\mathbf{4}}$

${\mathbf{ZrI}}_{\mathbf{4}}\stackrel{\mathbf{1800}\mathbf{ }\mathit{K}}{\mathbf{\to }}\mathbf{Z}\mathbf{r}\mathbf{\left(}\mathbf{p}\mathbf{u}\mathbf{r}\mathbf{e}\mathbf{\right)}\mathbf{+}\mathbf{2}{\mathbf{I}}_{\mathbf{2}}$

This method is known as ,

a) Liquation

b) Van Arkel process

c) Zone refining

d) Mond's process

Answer Key:

b) Van Arkel process 

  

18. Which of the following is used for concentrating ore in metallurgy?

a) Leaching

b) Roasting

c) Froth floatation

d) Both (a) and (c)

Answer Key:

d) Both (a) and (c) 

  

19. The incorrect statement among the following is

a) Nickel is refined by Mond's process

b) Titanium is refined by Van Arkel's process

c) Zinc blende is concentrated by froth floatation

d) In the metallurgy of gold, the metal is leached with dilute sodium chloride solution

Answer Key:

d) In the metallurgy of gold, the metal is leached with dilute sodium chloride solution 

  

20. In the electrolytic refining of copper, which one of the following is used as anode?

a) Pure copper

b) Impure copper

c) Carbon rod

d) Platinum electrode

Answer Key:

b) Impure copper 

  

21. Which of the following plot gives Ellingham diagram

a) $△$S Vs T

b) $△\mathrm{G}° \mathrm{Vs} \mathrm{T}$

c) $△\mathrm{G}° \mathrm{Vs} \frac{1}{\mathrm{T}}$

d) $△\mathrm{G}° \mathrm{Vs} {\mathrm{T}}^2$

Answer Key:

b) $△\mathrm{G}° \mathrm{Vs} \mathrm{T}$ 

  

22. In the Ellingham diagram, for the formation of carbon monoxide

a)  $\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">S</mi><mo\; mathvariant="bold">°</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">T</mi></mrow></mfrac></math>}\end{array}\right)$$$is negative

b) $\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">G</mi><mo\; mathvariant="bold">°</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">T</mi></mrow></mfrac></math>}\end{array}\right)$$$is positive

c) $\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">G</mi><mo\; mathvariant="bold">°</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">T</mi></mrow></mfrac></math>}\end{array}\right)$ is negative

d) $initially$$\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△T</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">G°</mi></mrow></mfrac></math>}\end{array}\right)$ is positive, after 700° C, $\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">G</mi><mo\; mathvariant="bold">°</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">T</mi></mrow></mfrac></math>}\end{array}\right)$ is negative

Answer Key:

c) $\left(\begin{array}{c}\mathrm{<math\; xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">G</mi><mo\; mathvariant="bold">°</mo></mrow><mrow><mo\; mathvariant="bold">△</mo><mi\; mathvariant="bold">T</mi></mrow></mfrac></math>}\end{array}\right)$ is negative

  

23. Which of the following reduction is not thermodynamically feasible?

a) $\mathbf{C}{\mathbf{r}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}\mathbf{+}\mathbf{2}\mathbf{A}\mathbf{l}\mathbf{\to }\mathbf{A}{\mathbf{l}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}\mathbf{+}\mathbf{2}\mathbf{C}\mathbf{r}$

b) $\mathbf{A}{\mathbf{l}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}+\mathbf{2}\mathbf{C}\mathbf{r}\to \mathbf{C}{\mathbf{r}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}+\mathbf{2}\mathbf{A}\mathbf{l}$

c) $\mathbf{3}\mathbf{T}\mathbf{i}{\mathbf{O}}_{\mathbf{2}}\mathbf{+}\mathbf{4}\mathbf{A}\mathbf{l}\to 2 \mathbf{A}{\mathbf{l}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}+3\mathrm{Ti}$

d) none of these

Answer Key:

b) $\mathbf{A}{\mathbf{l}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}+\mathbf{2}\mathbf{C}\mathbf{r}\to \mathbf{C}{\mathbf{r}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}+\mathbf{2}\mathbf{A}\mathbf{l}$ 

  

24. Which of the following is not true with respect to Ellingham diagram?

a) Free energy changes follow a straight line. Deviation occurs when there is a phase change.

b) The graph for the formation of CO₂ is a straight line almost parallel to free energy axis.

c) Negative slope of CO shows that it becomes more stable with increase in temperature.

d) Positive slope of metal oxides shows that their stabilities decrease with increase in temperature.

Answer Key:

b) The graph for the formation of CO₂ is a straight line almost parallel to free energy axis.

II.Short Answer Questions.

12th Chemistry

III. Long Answer Questions.

12th Chemistry

IV. Exercise.

12th Chemistry