CBSE Class 10 Science Metals and Non metals VBQs Set 03

Question. What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: The oxides which act as both acidic as well as basic are called amphoteric oxides, e.g. \( Al_2O_3 \) and \( ZnO \) are amphoteric oxides.

Question. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer: \( Zn \) and \( Al \) will displace hydrogen from dilute acids because they are more reactive than hydrogen whereas \( Cu \) and \( Ag \) cannot displace hydrogen from dilute acids because they are less reactive than hydrogen.
\( Zn(s) + 2HCl(dil) \)
\( \rightarrow \) \( ZnCl_2(aq) + H_2(g) \)
\( 2Al(s) + 6HCl(dil) \)
\( \rightarrow \) \( 2AlCl_3(aq) + 3H_2(g) \)

Question. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it.
(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
Answer: (a) (i) There will be no effect of gas on dry litmus paper.
(ii) Moist blue litmus paper will turn red.
(b) \( S(s) + O_2(g) \)
\( \rightarrow \) \( SO_2(g) \)
\( SO_2(g) + H_2O(l) \)
\( \rightarrow \) \( H_2SO_3(aq) \) (Sulphurous acid)
Sulphurous acid turns blue litmus red.

Question. State two ways to prevent the rusting of iron.
Answer: (i) Painting: Iron articles are painted so that surface does not come in contact with air and water and it does not get rusted.
(ii) Galvanisation: It is a process in which iron articles are coated with zinc metal so as to prevent them from rusting. Zinc is more reactive than iron, therefore, it loses electrons more readily and prevents iron from rusting.

Question. What type of oxides are formed when non-metals combine with oxygen?
Answer: Mostly acidic oxides are formed when non-metal combines with oxygen.

Question. Give reasons.
(i) Platinum, gold and silver are used to make jewellery.
(ii) Sodium, potassium and lithium are stored under oil.
(iii) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(iv) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer: (i) It is because they are highly lustrous and least reactive.
(ii) They are highly reactive. They catch fire and start burning when kept open in the air. To prevent their reaction with oxygen, moisture and carbon dioxide of air, they are stored under oil.
(iii) It is because aluminium is a good conductor of heat.
(iv) It is because it is easier to reduce oxide ores as compared to carbonates and sulphides.

Question. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer: It is because basic copper carbonate formed on copper vessel reacts with acid present in lemon or tamarind juice and gets dissolved and green layer is removed.

Question. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer:

• Metals can lose electrons easily to form positive ions; Non-metals can gain electrons easily to form negative ions.
• Metals form basic oxides; Non-metals form acidic oxides.
• Metals can displace hydrogen from dilute acids; Non-metals cannot displace hydrogen from dilute acids.
• Reactive metals can displace hydrogen from water or steam; Non-metals cannot displace hydrogen from water.

Question. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer: The solution he had used was aqua regia, which is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio \( 3 : 1 \). Aqua regia is one of the few reagents that is able to dissolve gold. When the person claimed to be goldsmith dipped bangles in aqua regia, some of the gold got dissolved and hence weight of the bangles got reduced.

Question. Give the reason why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer: Copper is better conductor of heat than steel therefore, it is used for making hot water tanks.

Question. Which one of the following metals do not react with cold as well as hot water?
(a) Na
(b) Ca
(c) Mg
(d) Fe
Answer: (d) Fe

Question. Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg)?
(a) \( H_2SO_4 \)
(b) HCl
(c) \( HNO_3 \)
(d) All of the options.
Answer: (c) \( HNO_3 \)

Question. Which of the following metals exist in their native state in nature?
(i) Cu
(ii) Au
(iii) Zn
(iv) Ag
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
Answer: (c) (ii) and (iv)

Question. Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
(i) Au
(ii) Cu
(iii) Na
(iv) K
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer: (a) (i) and (ii)

Question. 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)

Question. 2 mL each of concentrated HCl, \( HNO_3 \) and a mixture of concentrated HCl and concentrated \( HNO_3 \) 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) Ag
Answer: (b) Au

Question. 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) and (iv)
Answer: (b) (iii) and (iv)

Question. An element A is soft and can be cut with a knife. This is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following
(a) Mg
(b) Na
(c) P
(d) Ca
Answer: (b) Na

Question. Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which of the following alloys contain non-metal as one of its constituents?
(a) Brass
(b) Bronze
(c) Amalgam
(d) Steel
Answer: (d) Steel

Question. Which among the following alloys contain mercury as one of its constituents?
(a) Stainless steel
(b) Alnico
(c) Solder
(d) Zinc amalgam
Answer: (d) Zinc amalgam

Question. Reaction between X and Y, forms compound Z. X loses electron and Y gains electron. Which of the following properties is not shown by Z?
(a) Has high melting point
(b) Has low melting point
(c) Conducts electricity in molten state
(d) Occurs as solid
Answer: (b) Has low melting point

Question. The electronic configurations of three elements X, Y and Z are X — 2, 8; Y — 2, 8, 7 and Z — 2, 8, 2. Which of the following is correct?
(a) X is a metal
(b) Y is a metal
(c) Z is a non-metal
(d) Y is a non-metal and Z is a metal
Answer: (d) Y is a non-metal and Z is a metal

Question. Although metals form basic oxides, which of the following metals form an amphoteric oxide?
(a) Na
(b) Ca
(c) Al
(d) Cu
Answer: (c) Al

Question. Which of the following can undergo a chemical reaction?
(a) \( MgSO_4 \) + Fe
(b) \( ZnSO_4 \) + Fe
(c) \( MgSO_4 \) + Pb
(d) \( CuSO_4 \) + Fe
Answer: (d) \( CuSO_4 \) + Fe

Question. Which of the following property is generally not shown by metals?
(a) Electrical conduction
(b) Sonorous in nature
(c) Dullness
(d) Ductility
Answer: (c) Dullness

Question. The ability of metals to be drawn into thin wire is known as
(a) ductility
(b) malleability
(c) sonorousity
(d) conductivity
Answer: (a) ductility

Question. What happens when calcium is treated with water?
(i) It does not react with water
(ii) It reacts violently with water
(iii) It reacts less violently with water
(iv) Bubbles of hydrogen gas formed stick to the surface of calcium
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (ii)
(d) (iii) and (iv)
Answer: (d) (iii) and (iv)

Question. Which one of the following properties is not generally exhibited by ionic compounds?
(a) Solubility in water
(b) Electrical conductivity in solid state
(c) High melting and boiling points
(d) Electrical conductivity in molten state
Answer: (b) Electrical conductivity in solid state

Question. Which among the following statements is incorrect for magnesium metal?
(a) It burns in oxygen with a dazzling white flame
(b) It reacts with cold water to form magnesium oxide and evolves hydrogen gas
(c) It reacts with hot water to form magnesium hydroxide and evolves hydrogen gas
(d) It reacts with steam to form magnesium hydroxide and evolves hydrogen gas
Answer: (b) Mg reacts with hot water and not cold water.

Question. Generally, non-metals are not conductors of electricity. Which of the following is a good conductor of electricity?
(a) Diamond
(b) Graphite
(c) Sulphur
(d) Fullerene
Answer: (b) Graphite

Question. Electrical wires have a coating of an insulating material. The material, generally used is
(a) Sulphur
(b) Graphite
(c) PVC
(d) All can be used
Answer: (c) PVC

Question. Which of the following non-metals is a liquid?
(a) Carbon
(b) Bromine
(c) Phosphorus
(d) Sulphur
Answer: (b) Bromine

Question. Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.
Answer: Bring a burning candle near the gas. If it burns with pop sound, the gas is hydrogen and the element is a metal.
\( M + 2NaOH \)
\( \rightarrow \) \( Na_2MO_2 + H_2(g) \)
\( M + 2HCl \)
\( \rightarrow \) \( MCl_2 + H_2(g) \)

Question. During extraction of metals, electolytic refining is used to obtain pure metals.
(a) Which material will be used as anode and cathode for refining of silver metal by this process?
(b) Suggest a suitable electrolyte also.
(c) In this electrolytic cell, where do we get pure silver after passing electric current?
Answer: (a) Pure silver rod will be used as cathode and impure silver rod will be used as anode.
(b) \( AgNO_3(aq) \) can be used as electrolyte.
(c) Pure silver will be formed at cathode.
At anode : \( Ag \) \( \rightarrow \) \( Ag^+ + e^- \)
At cathode : \( Ag^+ + e^- \) \( \rightarrow \) \( Ag \)

Question. Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?
Answer: It is because it is easier to reduce metal oxides to get free metals as compared to metal sulphides and metal carbonates.

Question. Compound X and aluminium are used to join railway tracks.
(a) Identify the compound X.
(b) Name the reaction.
(c) Write down its reaction.
Answer: (a) ‘X’ is \( Fe_2O_3 \).
(b) It is called thermite reaction.
(c) \( 2Al(s) + Fe_2O_3(s) \)
\( \rightarrow \) \( Al_2O_3(s) + 2Fe(l) + heat \) (molten)
Molten iron is used to form broken railway tracks.

Question. When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.
Answer: Both sodium (Na) and potassium (K) react with cold water to give basic salt NaOH and KOH respectively. Since the molecular mass of XOH is 40, therefore, the metal X is Na. Since the molecular mass of NaOH is 40 (23 + 16 + 1 = 40). Therefore, Y is NaOH and the gas liberated during reaction is hydrogen. Thus, Z is \( H_2 \).
\( 2Na + 2H_2O \)
\( \rightarrow \) \( 2NaOH + H_2 + Heat energy \)

Question. The following reaction takes place when aluminium powder is heated with \( MnO_2 \):
\( 3MnO_2(s) + 4Al(s) \) \( \rightarrow \) \( 3Mn(l) + 2Al_2O_3(l) + Heat \)
(a) Is aluminium getting reduced?
(b) Is \( MnO_2 \) getting oxidised?
Answer: (a) No, aluminium is getting oxidised.
(b) No, \( MnO_2 \) is getting reduced.

Question. A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature? Identify A and B. Write down the reactions of oxide B with HCl and NaOH.
Answer: ‘A’ is aluminium.
\( 4Al(s) + 3O_2(g) \xrightarrow{heat} 2Al_2O_3(s) \)
‘B’ is \( Al_2O_3 \), amphoteric in nature.
\( Al_2O_3 + 6HCl \)
\( \rightarrow \) \( 2AlCl_3 + 3H_2O \)
\( Al_2O_3 + 2NaOH \)
\( \rightarrow \) \( 2NaAlO_2 + H_2O \)

Question. Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements:
(a) Mg and \( N_2 \)
(b) Li and \( O_2 \)
(c) Al and \( Cl_2 \)
(d) K and \( O_2 \)
Answer: (a) \( 3Mg + N_2 \) \( \rightarrow \) \( Mg_3N_2 \)
(b) \( 4Li + O_2 \) \( \rightarrow \) \( 2Li_2O \)
(c) \( 2Al + 3Cl_2 \) \( \rightarrow \) \( 2AlCl_3 \)
(d) \( 4K + O_2 \) \( \rightarrow \) \( 2K_2O \)

Question. A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas oxide C causes global warming.
(a) Identify A, B and C.
(b) To which group of periodic table does A belong?
Answer: (a) ‘A’ is carbon. It forms two oxides: CO (B) is toxic whereas \( CO_2 \) (C) causes global warming as it absorbs heat radiations from atmosphere.
(b) ‘A’ belongs to group 14 of periodic table.

Question. An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.
Answer: ‘A’ is calcium metal, ‘B’ is calcium hydroxide, ‘C’ is calcium oxide.
\( Ca(s) + 2H_2O(l) \)
\( \rightarrow \) \( Ca(OH)_2(aq) + H_2(g) \)
‘B’ \( Ca(OH)_2 \) is used in white washing.
\( Ca(OH)_2(aq) \xrightarrow{heat} CaO(s) + H_2O(l) \)
\( CaO(s) + H_2O(l) \)
\( \rightarrow \) \( Ca(OH)_2(aq) \)

Question. A non-metal A which is the largest constituent of air, when heated with \( H_2 \) in \( 1 : 3 \) ratio in the presence of catalyst (Fe) gives a gas B. On heating with \( O_2 \), it gives an oxide C. If this oxide is passed into water in the presence of air, it gives an acid D which acts as a strong oxidising agent.
(a) Identify A, B, C and D.
(b) To which group of periodic table does this non-metal belong?
Answer: (a) \( N_2 \) is largest constituent of air, when heated with \( H_2 \) in the ratio of \( 1 : 3 \) in the presence of catalyst (Fe) gives a gas \( NH_3 \)(B).
\( N_2(g) + 3H_2(g) \xrightarrow{773 K, Fe} 2NH_3(s) \)
Nitrogen reacts with oxygen on heating to form nitrogen monoxide ‘C’, which gets oxidised in the presence of \( O_2 \) to nitrogen dioxide. Nitrogen dioxide dissolves in water in the presence of oxygen to form nitric acid which is an oxidising agent.
\( N_2(g) + O_2(g) \xrightarrow{heat} 2NO \)
\( 2NO + O_2 \) \( \rightarrow \) \( 2NO_2 \)
\( 4NO_2 + 2H_2O + O_2 \) \( \rightarrow \) \( 4HNO_3 \) (Nitric acid)
‘A’ is \( N_2 \), ‘B’ is \( NH_3 \), ‘C’ is \( NO \) and ‘D’ is \( HNO_3 \).
(b) Group 15