VARDAAN LEARNING INSTITUTE

Solve these identification problems:

1. A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y, Z.
2. Element X reacts with oxygen to produce a compound with a high melting point. This compound is also soluble in water. The element X is likely to be Calcium, Carbon, Silicon or Iron? Justify.
3. A metal M does not react with cold water but reacts with hot water to form its hydroxide. Metal M floats during the reaction. Identify M.
4. A metal X is stored under kerosene. When a small piece of it is left open in the air, it catches fire. When the product formed is dissolved in water, it turns red litmus blue. Identify X.
5. An element A burns with a golden flame in air. It reacts with another element B, atomic number 17, to give a product C. An aqueous solution of C conducts electricity. Identify A, B, C.
6. Carbon cannot reduce the oxides of Sodium, Magnesium, and Aluminium to their respective metals. Why? Which method is used then?

7. Give reasons:
   (a) Platinum, Gold and Silver are used to make jewellery.
   (b) Sodium, Potassium and Lithium are stored under oil.
   (c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
   (d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
8. A student was given Mn, Zn, Fe and Cu metals. Identify which of them:
   (a) Will not displace H$_2$ from dilute HCl.
   (b) Will react only with steam to evolve H$_2$ gas.
   (c) Will give H$_2$ with 5% HNO$_3$.
9. State the conditions under which the following metals react with water:
   (a) Magnesium
   (b) Iron
   (c) Sodium
   Write chemical equations for each.
10. Explain the following:
    (a) Reactivity of Al decreases if it is dipped in HNO$_3$.
    (b) Carbon cannot reduce the oxides of Na or Mg.

11. Thermite Reaction: A brown substance 'X' on heating with Aluminium powder gives off a lot of heat and the metal 'Y' is produced in molten state. This reaction is used to join railway tracks.
    (a) Identify X and Y.
    (b) Write the balanced chemical equation.
    (c) What type of reaction is this? (Displacement/Exothermic/Redox).
12. Draw the electron dot structure for the formation of Calcium Oxide ($CaO$). (Atomic No: Ca=20, O=8).
13. In the electrolytic refining of Copper:
    (a) What is used as Anode and Cathode?
    (b) What happens to the impurities driven out from the anode?
    (c) Write the reaction at Cathode.
14. An ore on heating in air produces Sulphur Dioxide gas. Which process would you suggest for its concentration? Describe the process briefly.
15. You are given a hammer, a battery, a bulb, wires, and a switch.
    (a) How could you use them to distinguish between samples of metals and non-metals?
    (b) Assess the usefulness of these tests in distinguishing metals and non-metals.