VARDAAN LEARNING INSTITUTE

1. Amphoteric Nature Proof: Aluminium Oxide ($Al_2O_3$) is amphoteric in nature. Prove this statement by writing balanced chemical equations for its reaction with:
   (a) Hydrochloric Acid ($HCl$)
   (b) Sodium Hydroxide ($NaOH$)
2. Nitric Acid Exception: Generally, when metals react with dilute acid, Hydrogen gas is evolved. But when metals react with dilute Nitric acid ($HNO_3$), $H_2$ gas is NOT evolved.
   (a) Why? (Explain the oxidizing nature).
   (b) Name two metals which react with very dilute $HNO_3$ to evolve $H_2$ gas.
3. Aqua Regia: Royal Water is a freshly prepared mixture of two concentrated acids.
   (a) Name the two acids.
   (b) What is the ratio of their mixture?
   (c) Which noble metal can it dissolve?
4. Explain the mechanism of electrolytic refining of Copper. Why does the anode thin down and cathode get thickened? What is the role of the electrolyte?
5. Why is it that non-metals do not displace hydrogen from dilute acids? (Hint: Electron acceptance vs donation).

Case I: Extraction of Mercury. Cinnabar ($HgS$) is an ore of Mercury. When it is heated in air, it is first converted into mercuric oxide ($HgO$). Mercuric oxide is then reduced to mercury on further heating.

6. Write the chemical equation for the conversion of Cinnabar to Mercuric Oxide.
7. Write the equation for the reduction of Mercuric Oxide to Mercury.
8. Is Carbon required for the reduction of HgO? Why/Why not?
9. What happens if Cinnabar is heated in limited supply of air?

Case II: Reactivity Lab. Four metals A, B, C and D are taken.
- A displaces B from its salt solution.
- B displaces D from its salt solution.
- C does not react with any salt solution of A, B or D.
- D displaces Hydrogen from dilute acid.

10. Arrange metals A, B, C, D in decreasing order of reactivity.
11. Which is the most reactive metal?
12. Container of which metal can be used to store the salt solution of B? (A or C?)
13. If metal B is Iron, what could be metal A? (Copper/Zinc).

14. Give the steps involved in the extraction of Zinc from Zinc Sulphide. Write all equations including Roasting and Reduction.
15. Assertion(A): Sodium can be extracted by electrolysis of aqueous solution of NaCl (Brine).
    Reason(R): Sodium is highly reactive.
    Critique the assertion. (Hint: H+ gets discharged instead of Na+ in aqueous).
16. Why do we apply oil on iron tools when they are not in use?
17. An element E forms an oxide $E_2O$. An aqueous solution of $E_2O$ turns red litmus paper blue.
    (a) What is the nature of the oxide $E_2O$?
    (b) State whether element E is a metal or a non-metal.
    (c) Give an example of an element like E.
18. Metals like Iron, Zinc and Lead occur as sulphides or carbonates in nature. It is easier to extract metal from its oxide than from its sulphide or carbonate. Name the processes used to convert sulphide and carbonate ores into oxides respectively.