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Thursday, August 9, 2012

Chemistry X Metals and Non-metals Solved exam questions Term-1

Short Answer Type Questions:- (3 marks)
Q.1:- Write suitable example, explain how a metal low in the activity series can be extracted?
Ans:- Metals low in the activity series are less reactive. The oxides of these metals can be reduced to metals by heating alone. For example, extraction of Mercury (Hg) from Cinnabar (HgO).
2HgS(s) + 3O2(g) heat--------à   2HgO(s) + 2SO2(g)
2HgO(s) heat ---------------à   2Hg(l) + O2(g)
Q.2:- Write three properties of ionic compounds.
Ans:- (i) Ionic compounds have high melting points. (ii) Ionic compounds are soluble in water. (iii) Ionic compounds conduct electricity in aqueous and molten state.
Q.3. What is anodizing? What is its use?
Ans. The process of forming a thick oxide layer of aluminium oxide that makes it resistant to further corrosion.
Q.4. What is aqua regia? What is its use?
Ans. Aqua regia is a mixture of conc. HCl and conc. HNO3 in the ratio 3:1. It can dissolve gold and platinum.
Q.5. What do you mean by thermite reaction? What is its use?
Ans. The reaction between Iron(II) oxide Fe2O3 with Al is used to join rail track joints or cracked machine parts. This reaction is known as thermit reaction.
Fe2O3 (s) + 2Al (s) 2Fe (l) + Al2O3 (s) + Heat
Q.6. Why active metals do not liberate H2 gas when treated with dil. HNO3?
Ans. This is because HNO3 is strong oxidizing agent. It oxidizes H2 produced to water and itself gets reduced to nitrogen oxides.
Q.7. Sometimes the ore itself acts as a reducing agent. Give an example.
Ans. During roasting of Cu2S, the ore itself acts as a reducing agent.
2CuS (s) + 3O2(g)         --------→ 2Cu2O(s) + 2SO2(g)
2Cu2O + Cu2S              -----------→ 6Cu(s) + SO2(g)

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