CBSE Class 10 Science HOTs Metals and Non Metals Set 03

Question. Among the following the metal with lowest density is 
(a) Lithium
(b) Lead
(c) Magnesium
(d) Aluminium
Answer: (a) Lithium

Question. The compound obtained on reaction of iron with steam is/are:
(a) \( Fe_2O_3 \)
(b) \( Fe_3O_4 \)
(c) \( FeO \)
(d) \( Fe_2O_3 \) and \( Fe_3O_4 \)
Answer: (b) \( Fe_3O_4 \)

Question. Which one of the following 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

Question. The chemical reaction between Cu and nitric acid is given by chemical equation \( Cu + 4HNO_{3(conc.)} \rightarrow Cu(NO_3)_2 + 2NO_2 + 2H_2O \). Which of the following is correct?
(a) Copper oxidises \( HNO_3 \) to \( NO_2 \)
(b) \( HNO_3 \) gets oxidised to \( H_2O \)
(c) \( HNO_3 \) gets reduced to \( NO_2 \)
(d) None of the options
Answer: (c) \( HNO_3 \) gets reduced to \( NO_2 \)

Question. \( Pb(s) + CuCl_{2(aq)} \rightarrow PbCl_{2(aq)} + Cu(s) \). Which option explains reason for formation of \( PbCl_2 \)?
(a) Copper is more reactive than lead
(b) Lead is less reactive than Cu
(c) Pb and Cu are equally reactive
(d) Lead is more reactive than Cu
Answer: (d) Lead is more reactive than Cu

Question. Aluminium strip is dipped in \( FeSO_{4(aq)} \) and change that is observed, is
(a) Green colour changes to brown
(b) Lower end of test tube becomes warm
(c) Coloured gas with smell of burning sulphur
(d) None of the options
Answer: (a) Green colour changes to brown

Question. Copper is used for making utensils. Which of the following physical properties of copper is not responsible for the same?
(a) Malleability
(b) High melting point
(c) Thermal conductivity
(d) High reactivity
Answer: (d) High reactivity

Question. The most abundant element in the universe is
(a) Hydrogen
(b) Helium
(c) Carbon
(d) Oxygen
Answer: (a) Hydrogen

Question. Which of the following is not an ionic compound?
(a) \( KCl \)
(b) \( MgCl_2 \)
(c) \( HCl \)
(d) \( NaCl \)
Answer: (c) \( HCl \)

Question. A gas is evolved when dil. sulphuric acid reacts with zinc granules. It gives a pop sound when lit match stick is introduced near it. Identify the gas.
(a) Nitrogen
(b) Hydrogen
(c) Oxygen
(d) Carbon dioxide
Answer: (b) Hydrogen

Question. Metal X reacts with dil. \( HCl \) to form metal salt and gas. Identify X.
(a) Copper
(b) Mercury
(c) Silver
(d) Zinc
Answer: (d) Zinc

Question. When zinc reacts with sodium hydroxide, the product formed is 
(a) Sodium oxide
(b) Sodium zincate
(c) Zinc hydroxide
(d) Zinc oxide
Answer: (b) Sodium zincate

Question. The reason for different behaviour (floating) of Mg in dil \( HCl \) is due to:
(a) Mg is lighter element than dil. \( HCl \).
(b) Mg reacts with dil. \( HCl \) to produce \( H_2 \) gas which helps in floating.
(c) Mg reacts with dil. \( HCl \) to produce \( N_2 \) gas which helps in floating.
(d) Mg reacts with dil. \( HCl \) to produce \( CO_2 \) gas which helps in floating. 
Answer: (b) Mg reacts with dil. \( HCl \) to produce \( H_2 \) gas which helps in floating.

Question. Which of the following solutions are electrolytes?
I. Dil. \( HCl \)
II. Sugar Solution
III. Alcohol in water
IV. Lime water
(a) I and II
(b) I and IV
(c) II, III and IV
(d) I, II and IV 
Answer: (b) I and IV

Question. (a) Why is potassium kept immersed in kerosene? 
(b) Write the name of an allotrope of carbon. 
Answer: (a) Potassium is highly reactive and reacts vigorously with oxygen and moisture in the air. To prevent accidental fires and its reaction with air, it is kept immersed in kerosene.
(b) Diamond (or Graphite/Fullerene).

Question. (a) Name any one metal which reacts neither with cold water nor with hot water, but reacts with heated steam to produce hydrogen gas.
(b) Arrange the following metals in the decreasing order of reactivity: Na, K, Cu, Ag
Answer: (a) Iron (or Zinc/Aluminium).
(b) K > Na > Cu > Ag.

Question. (a) 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 and Z. 
(b) Which metal does not react with water at all? 
Answer: (a) X is Carbon, Y is Diamond, and Z is Graphite.
(b) Gold (or Silver/Copper/Platinum).

Question. When metal reacts with nitric acid, \( H_2 \) is not evolved why?
Answer: Nitric acid is a strong oxidising agent. It oxidises the hydrogen produced to water and itself gets reduced to any of the nitrogen oxides (\( NO_2, NO, N_2O \)).

Question. From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal (a) which reacts with water only on boiling, and (b) another which does not react even with steam.
Answer: (a) Magnesium reacts with hot water (boiling water).
(b) Copper does not react even with steam.

Question. Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than 310 K (37°C).
Answer: Liquid metal: Mercury; Liquid non-metal: Bromine. Two metals with low melting point: Gallium and Caesium.

Question. Give reason why: (a) gold and silver are used for making jewellery. (b) a few metals are used for making cooking utensils. 
Answer: (a) Gold and silver are highly lustrous and very less reactive (noble metals), so they do not corrode easily. They are also highly malleable and ductile.
(b) Metals are good conductors of heat and have high melting points, making them suitable for cooking.

Question. (a) Give reason for the following:
(i) Aluminium oxide is considered as an amphoteric oxide.
(ii) Ionic compounds conduct electricity in molten state.
(b) Name the metal:
(i) Which has low melting point.
(ii) Which exist in liquid state at room temperature.
(iii) Which is most abundant in earth’s crust.
(iv) Which is placed at the top of the reactivity series.
Answer: (a) (i) Aluminium oxide reacts with both acids and bases to form salt and water.
(ii) In the molten state, the electrostatic forces of attraction between oppositely charged ions are overcome due to heat, and ions become free to move and conduct electricity.
(b) (i) Gallium (or Caesium); (ii) Mercury; (iii) Aluminium; (iv) Potassium.

Question. How do metals reacts with dilute acids? Explain with the help of an example.
Answer: Metals react with dilute acids to form salt and hydrogen gas. For example, Zinc reacts with dilute sulphuric acid to form zinc sulphate and hydrogen gas:
\( Zn(s) + H_2SO_{4(dil.)} \rightarrow ZnSO_{4(aq)} + H_{2(g)} \)

Question. Give the names and formulae of (a) two acidic oxides (b) two basic oxides
Answer: (a) Acidic oxides: Carbon dioxide (\( CO_2 \)), Sulphur dioxide (\( SO_2 \)).
(b) Basic oxides: Sodium oxide (\( Na_2O \)), Calcium oxide (\( CaO \)).

Question. (a) Why are ionic compounds generally hard?
(b) Name the solvent in which ionic compounds are generally soluble.
(c) Why are aqueous solutions of ionic compounds able to conduct electricity?
Answer: (a) Due to strong electrostatic forces of attraction between oppositely charged ions.
(b) Water.
(c) In aqueous solution, ionic compounds dissociate into ions which are free to move and carry electric current.

Question. A metal ‘X’ loses two electrons and a non-metal ‘Y’ gains one electron. Show the electron dot structure of compound formed between them. Is it ionic or covalent? Does it have high melting point or low? Will it conduct electricity in solid state or in aqueous solution and why? Will it be soluble in water?
Answer: The compound formula is \( XY_2 \). It is an ionic compound. It has a high melting point. It will conduct electricity in aqueous solution because ions become free to move. It will be soluble in water. (Electron dot: \( X^{2+} [:\ddot{Y}:]^-_2 \))

Question. Show the formation of magnesium chloride with the help of electron dot structure.
Answer: \( Mg \rightarrow Mg^{2+} + 2e^- \) (2, 8, 2 \( \rightarrow \) 2, 8); \( 2Cl + 2e^- \rightarrow 2Cl^- \) (2, 8, 7 \( \rightarrow \) 2, 8, 8). Transfer of two electrons from one Mg atom to two Cl atoms forms \( Mg^{2+}[Cl]^-_2 \).

Question. What happens when (a) Zinc reacts with copper sulphate solution (b) Aluminum reacts with steam (c) Sodium reacts with water. Give balanced equations for each. [KVS]
Answer: (a) \( Zn(s) + CuSO_{4(aq)} \rightarrow ZnSO_{4(aq)} + Cu(s) \)
(b) \( 2Al(s) + 3H_2O(g) \rightarrow Al_2O_{3(s)} + 3H_{2(g)} \)
(c) \( 2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_{2(g)} \)

Question. (a) Show the formation of \( Na_2O \) by the transfer of electrons between the combining atoms. (b) Why are ionic compounds usually hard? (c) How is it that ionic compounds in the solid state do not conduct electricity but they do so when in molten state? 
Answer: (a) Two sodium atoms each lose one electron to one oxygen atom which gains two electrons, forming \( [Na]^+_2 [O]^{2-} \).
(b) Due to strong electrostatic forces of attraction between ions.
(c) In solid state, ions are fixed in their crystal lattice and cannot move. In molten state, heat breaks these forces and ions move freely to conduct current.

Question. A student was given Mn, Zn, Fe and Cu metals. Identify which of them (a) will not displace \( H_2 \) from dil. HCl. (b) will react only with steam to give \( H_2(g) \). (c) will give \( H_2 \) with 5% \( HNO_3 \). Write the chemical reactions involved. 
Answer: (a) Copper (Cu).
(b) Iron (Fe). Reaction: \( 3Fe + 4H_2O(g) \rightarrow Fe_3O_4 + 4H_2 \).
(c) Manganese (Mn). Reaction: \( Mn + 2HNO_{3(5\%)} \rightarrow Mn(NO_3)_2 + H_2 \).

Question. With the help of a suitable example, explain how ionic compounds are formed. State any three general properties of ionic compounds.
Answer: Ionic compounds are formed by the complete transfer of electrons from a metal to a non-metal. Example: Formation of NaCl from Na and Cl. Properties: (i) High melting and boiling points. (ii) Soluble in water. (iii) Conduct electricity in molten state or aqueous solution.

Question. Four metals A, B, C and D are added to the following aqueous solutions one by one. The observations made are tabulated below:
| Metal | Iron (II) sulphate | Copper (II) sulphate | Zinc sulphate | Silver nitrate |
| A | No reaction | Reddish brown deposit | — | — |
| B | Grey deposit | — | No reaction | — |
| C | No reaction | No reaction | No reaction | White shining deposit |
| D | No reaction | No reaction | No reaction | No reaction |
Answer the following questions based on the above observations:
(a) Which is the most active metal and why?
(b) What would be observed if B is added to a solution of copper (II) sulphate and why?
(c) Arrange the metals A, B, C and D in order of increasing reactivity.
(d) Container of which metal can be used to store both zinc sulphate solution and silver nitrate solution?
(e) Which of the above solutions can be easily stored in a container made up of any of these metals?
Answer: (a) B is the most active because it displaces iron.
(b) B will displace copper and a reddish brown deposit will be formed because B is more reactive than iron, which is more reactive than copper.
(c) D < C < A < B.
(d) Metal D.
(e) Zinc sulphate solution (since no metal A, B, C, D can displace Zinc except B, but the table shows no reaction for B with ZnSO4).

Occurrence and Extraction of Metals, Corrosion, Alloys

Question. Copper becomes green when exposed to air for a long time due to
(a) formation of CuO on the surface
(b) formation of basic copper carbonate on surface
(c) formation of copper hydroxide on the surface
(d) none of the options
Answer: (b) formation of basic copper carbonate on surface

Question. In stainless steel, iron metal is alloyed with
(a) Cu and Cr
(b) Cr and Ni
(c) Cr and Sn
(d) Cu and Ni [KVS]
Answer: (b) Cr and Ni

Question. The process of heating sulphide ore in presence of air is called
(a) roasting
(b) calcination
(c) smelting
(d) electrolytic refining
Answer: (a) roasting

Question. The process in which carbonate ore is heated strongly in absence of air is called
(a) roasting
(b) calcination
(c) smelting
(d) reduction
Answer: (b) calcination

Question. Which of the statements about the reaction, \( ZnO + CO \rightarrow Zn + CO_2 \) is correct?
(a) ZnO is being oxidised
(b) CO is being reduced
(c) \( CO_2 \) is being oxidised
(d) ZnO is being reduced
Answer: (d) ZnO is being reduced

Question. Bauxite is mixed with cryolite so as to
(i) reduce its melting point
(ii) increase its electrical conductivity
(iii) molten cryolite acts as solvent
(iv) increase its melting point
(a) (i), (ii) and (iii)
(b) (ii), (iii) and (iv)
(c) (iii) and (iv)
(d) (i) and (ii)
Answer: (a) (i), (ii) and (iii)

Question. In electrolytic refining of copper, the electrolyte used is
(a) CuO
(b) \( Cu(OH)_2 \)
(c) Acidified \( CuSO_{4(aq)} \)
(d) \( CuSO_{4(s)} \)
Answer: (c) Acidified \( CuSO_{4(aq)} \)