Metals & Non-metals - Class 10th Science
Exemplar Solution MCQs-2
Question: 13. Silver articles become black on prolonged exposure to air. This is due to the formation of
(a) Ag3N
(b) Ag2O
(c) Ag2S
(d) Ag2S and Ag3N
Answer: (c) Ag2S
Explanation: Silver gets tarnished after the reaction of sulphur present in air. Because of formation of layer of silver sulphide, silver articles become black on prolonged exposure to air.
Thus, option (c) Ag2S is the correct answer.
Question: 14. Galvanisation is a method of protecting iron from rusting by coating with a thin layer of
(a) Gallium
(b) Aluminium
(c) Zinc
(d) Silver
Answer: (c) Zinc
Explanation: In the process of galvanization iron is covered by a coat of zinc. This layer of zinc prevents iron from getting rusted. Water pipes are come with galvanization.
Question: 15. Stainless steel is very useful material for our life. In stainless steel, iron is mixed with
(a) Ni and Cr
(b) Cu and Cr
(c) Ni and Cu
(d) Cu and Au
Answer: (a) Ni and Cr
Explanation:
Stainless steel is an alloy of iron, nickel and chromium. Process of alloying makes a metal strong, durable and corrosion resistant.
Question: 16. If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of
(a) CuSO4
(b) CuCO3
(c) Cu(NO3)2
(d) CuO
Answer: (b) CuCO3
Explanation: Copper gets blacken because of formation of a layer of carbonate over it due to reaction with carbon dioxide gas present in air. This is called tarnishing of copper.
Thus, answer is (b) CuCO3
Question: 17. Generally, metals are solid in nature. Which one of the following metals is found in liquid state at room temperature?
(a) Na
(b) Fe
(c) Cr
(d) Hg
Answer: (d) Hg
Explanation: Mercury is the only metal which is found in liquid state at room temperature. Other all metals are solid at room temperature.
Question: 18. Which of the following metals are obtained by electrolysis of their chlorides in molten state ?
(i) Na
(ii) Ca
(iii) Fe
(iv) Cu
(a) (i) and (iv)
(b) (iii) and (iv)
(c) (i) and (iii)
(d) (i) and (ii)
Answer: (d) (i) and (ii)
Explanation: Sodium and calcium fall towards the top of reactivity series. Since, sodium and calcium are very reactive so these metals cannot be reduced to pure form from their oxides or carbonates.
Thus, sodium and calcium are obtained by the process of electrolysis of their chlorides.
Question: 19. Generally, non-metals are not lustrous. Which of the following nonmetal is lustrous?
(a) Sulphur
(b) Oxygen
(c) Nitrogen
(d) Iodine
Answer: (d) Iodine
Explanation: Iodine and graphite are non-metals which shine and are lustrous.
Thus, option (d) Iodine is correct answer.
Question: 20. Which one of the following four metals would be displaced from the solution of its salts by other three metals?
(a) Mg
(b) Ag
(c) Zn
(d) Cu
Answer: (b) Ag
Explanation:
Since silver (Ag) is the least reactive metal among the option given. Thus, silver (Ag) would be displaced from the solution of its salt by other given three metals, i.e. Mangnesium (Mg), Zinc (Zn) and Copper (Cu).
Question: 21. 2 mL each of concentrated HCl, HNO3 and a mixture of concentrated HCl and concentrated HNO3 in the ratio of 3 : 1 were taken in test tubes labelled as A, B and C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be
(a) Al
(b) Au
(c) Cu
(d) Pt
Answer: (b) Au
Explanation: Test tube C contains mixture of concentrated HCl and concentrated HNO3 in the ratio of 3 : 1. This mixture is called Aqua-regia. Aqua-regia dissolves gold in it while hydrochloric acid and nitric acid do not.
Thus, metal taken was Gold (Au).
Question: 22. An alloy is
(a) an element
(b) a compound
(c) a homogeneous mixture
(d) a heterogeneous mixture
Answer: (c) a homogeneous mixture
Explanation: Alloy is a homogeneous mixture of two or more metals. For example stainless steel, bronze, brass, etc.
Question: 23. An electrolytic cell consists of
(i) positively charged cathode
(ii) negatively charged anode
(iii) positively charged anode
(iv) negatively charged cathode
(a) (i) and (ii)
(b) (iii) and (iv)
(c) (i) and (iii)
(d) (ii) ad (iv)
Answer: (b) (iii) and (iv)
Explanation:
Positively charged ions are called cations because it is deposited at negatively charged pole. And negatively charged ions are called anions because these are deposited at positively charged pole. This is the cause that negatively charged pole is called cathode and positively charged pole is called anode.
Thus, an electrolytic cell consists of a positively charged anode and a negatively charged cathode.
Question: 24. During electrolytic refining of zinc, it gets
(a) deposited on cathode
(b) deposited on anode
(c) deposited on cathode as well as anode
(d) remains in the solution
Answer: (a) deposited on cathode
Explanation:
Since, ions of zinc are positively charged, therefore while electrolytic refining of zinc, zinc deposited at cathode (negatively charged pole).