Metals and Non-metals
Multiple Choice Questions
1. Which of the following property is generally not shown by metals?
(a) Electrical conduction
(b) Sonorous in nature
(c) Dullness
(d) Ductility
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Answer
(c) Dullness
2. The ability of metals to be drawn into thin wire is known as
(a) ductility
(b) malleability
(c) sonorousity
(d) conductivity
Show Answer
Answer
(a) ductility
Explanation
- Ductility is property of metals to be drawn into thin wire.
- Malleability is property of metals to be drawn into thin wire
- Sonorousity is the ability of metal to be sonorous in nature
- Conductivity is the ability to conduct electricity
3. Aluminium is used for making cooking utensils. Which of the following properties of aluminium are responsible for the same?
(i) Good thermal conductivity
(ii) Good electrical conductivity
(iii) Ductility
(iv) High melting point
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (iv)
Show Answer
Answer
(d) (i) and (iv)
Explanation
Ductility and electric conductivity has no relation to cooking hence thermal conductivity and high melting point are the right answers.
4. Which one of the following metals do not react with cold as well as hot water?
(a) $Na$
(b) Ca
(c) $Mg$
(d) $Fe$
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Answer
(d) Fe
Explanation
Sodium and Calcium reacts vigorously with water and Magnesium reacts with hot water to form Magnesium Oxide. Iron does not react with cold and hot water but it reacts with steam.
5. Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?
(a) $FeO$
(b) $Fe_2 O_3$
(c) $Fe_3 O_4$
(d) $Fe_2 O_3$ and $Fe_3 O_4$
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Answer
(c) $Fe_3O_4$
Explanation
$3 Fe+4 H_2 O \longrightarrow Fe_3 O 4+4 H_2$
6. 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)
Show Answer
Answer
(d) (iii) and (iv)
Explanation
Calcium reacts vigorously with water and forms hydrogen which will make calcium to float.
7. 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) $H_2 SO_4$
(b) $HCl$
(c) $HNO_3$
(d) All of these
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Answer
(c) $HNO_3$
Explanation
Nitric acid is a powerful oxidizing agent. It reacts with metal to form water.
8. The composition of aqua-regia is
$ \begin{array}{ccl} \text {(a) Dil.HCl } & : & \text { Conc. } \mathrm{HNO}_3 \\ 3 & : & 1 \\ \text {(b) Conc. } \mathrm{HCl} & : & \text { Dil. } \mathrm{HNO}_3 \\ 3 & : & 1 \\ \text {(c) Conc. } \mathrm{HCl} & : & \text { Conc. } \mathrm{HNO}_3 \\ 3 & : & 1 \\ \text {(d) Dil. } \mathrm{HCl} & : & \text { Dil. } \mathrm{HNO}_3 \\ 3 & : & 1 \end{array} $
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Answer
$ \begin{array}{ccl} \text {(c) Conc. } \mathrm{HCl} & : & \text { Conc. } \mathrm{HNO}_3 \\ 3 & : & 1 \\ \end{array} $
9. Which of the following are not ionic compounds?
(i) $KCl$
(ii) $HCl$
(iii) $CCl_4$
(iv) ${N a C l}$
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iii)
Show Answer
Answer
(b) (ii) and (iii)
Explanation
$HCl$ and $CCl_4$ are covalent compound hence they cannot be ionic.
10. 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
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Answer
(b) Electrical conductivity in solid state
Explanation
In ionic compound free ions are not available in solid state hence solid ionic compounds cannot conduct electricity.
11. Which of the following metals exist in their native state in nature?
(i) ${C u}$
(ii) $Au$
(iii) ${Z n}$
(iv) ${A g}$
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)
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Answer
(c) (ii) and (iv)
Explanation
Gold and silver are non-reactive metals because of they are non-reactive they exist in native state in nature.
12. Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
(i) $Au$
(ii) ${C u}$
(iii) $Na$
(iv) $K$
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Show Answer
Answer
(d) (iii) and (iv)
Explanation
Sodium and potassium are at the top in reactivity series hence they can be refined by electrolytic refining.
13. Silver articles become black on prolonged exposure to air. This is due to the formation of
(a) $Ag_3 N$
(b) $Ag_2 O$
(c) $Ag_2 S$
(d) $Ag _2 S$ and $Ag_3N$
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Answer
(c) $Ag_2 S$
Explanation
Silver metal reacts with sulphur present in the atmosphere to form $Ag_2 S$. $Ag_2 S$ is responsibkle foer black coloration of silver articles.
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
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Answer
Answer is(c) Zinc
Explanation
Galvanization is a process of applying a layer of Zinc on iron by using electrolysis.
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 $Au$
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Answer
(a) $Ni$ and $Cr$
Explanation
Stainless steel is an alloy of Iron, Nicker and chromium. This alloy makes the metal strong, durable and corrosion resistant.
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) $CuSO _4$
(b) $CuCO _3$
(c) $Cu(NO_3) _2$
(d) $CuO$
Show Answer
Answer
(d) $CuO$
Explanation
On exposure to air copper reacts to atmospheric oxygen to form copper oxide layer which is green in color.
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) $Hg$
Show Answer
Answer
(d) $Hg$
18. Which of the following metals are obtained by electrolysis of their chlorides in molten state?
(i) $Na$
(ii) ${C a}$
(iii) $Fe$
(iv) $Cu$
(a) (i) and (iv)
(b) (iii) and (iv)
(c) (i) and (iii)
(d) (i) and (ii)
Show Answer
Answer
(d) (i) and (ii)
Explanation
Sodium and Calcium are in the top in reactivity series
19. Generally, non-metals are not lustrous. Which of the following nonmetal is lustrous?
(a) Sulphur
(b) Oxygen
(c) Nitrogen
(d) Iodine
Show Answer
Answer
(d) Iodine
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) $Cu$
Show Answer
Answer
(b) Ag
Explanation
Because silver is a non-reactive metal it can be displaced easily.
21. $2 mL$ 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) ${P t}$
Show Answer
Answer
(b) Au
Explanation
gold because solution C is mixture of Concentrated HCL and Concentrated $HNO_3$ which is called aqua rezia. Aqua Rezia dissolves gold.
22. An alloy is
(a) an element
(b) a compound
(c) a homogeneous mixture
(d) a heterogeneous mixture
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Answer
(c) a homogeneous mixture
Explanation
An Alloy is a homogeneous mixture because its composition is uniform.
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)
Show Answer
Answer
(b) (iii) and (iv)
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
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Answer
(a) deposited on cathode
Explanation
Zinc is positively charged hence it moves towards negatively charged cathode.
25. 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) $Ca$
Show Answer
Answer
(b) $Na$
Explanation
Sodium is soft which can be cut with a knife. Sodium reacts with water and air vigorously hence it is kept in kerosene.
26. Alloys are homogeneous mixtures of a metal with a metal or nonmetal. Which among the following alloys contain non-metal as one of its constituents?
(a) Brass
(b) Bronze
(c) Amalgam
(d) Steel
Show Answer
Answer
(d) Steel
Explanation
Steel is an alloy made up of carbon and iron where carbon is a non-metal.
27. 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
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Answer
(b) It reacts with cold water to form magnesium oxide and evolves hydrogen gas
Explanation
Magnessium reacts with cold water to form magnesium oxide and evolves hydrogen gas is a wrong statement because Magnessium Hydroxide is formed not Magnessium oxide.
28. Which among the following alloys contain mercury as one of its constituents?
(a) Stainless steel
(b) Alnico
(c) Solder
(d) Zinc amalgam
Show Answer
Answer
(d) Zinc amalgam
Explanation
Zinc amalgam is an alloy of Mercury and Zinc
29. 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
Show Answer
Answer
(b) Has low melting point
Explanation
Here $Z$ is an ionic compound and Ionic compounds have melting point hence option b) is a wrong statement.
30. 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
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Answer
(d) $Y$ is a non-metal and $Z$ is a metal
Explanation
Element $Y$ has 3 electron in its outer which is electronegative in nature. $Z$ has 2 electrons in its outermost shell hence it is electropositive. Hence it is a metal.
31. Although metals form basic oxides, which of the following metals form an amphoteric oxide?
(a) $Na$
(b) Ca
(c) Al
(d) $Cu$
Show Answer
Answer
(c) Al
Explanation
Oxides of Aluminum are both acidic and basic in nature. Hence aluminum oxides are amphoteric in nature.
32. 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
Show Answer
Answer
(b) Graphite
33. Electrical wires have a coating of an insulting material. The material, generally used is
(a) Sulphur
(b) Graphite
(c) PVC
(d) All can be used
Show Answer
Answer
(c) PVC
Explanation
Sulphur is brittle in nature, hence it can be used and Graphite is a good conductor of electricity hence it cannot be used as insulator.
34. Which of the following non-metals is a liquid?
(a) Carbon
(b) Bromine
(c) Phosphorus
(d) Sulphur
Show Answer
Answer
(b) Bromine
35. Which of the following can undergo a chemical reaction?
(a) $MgSO_4+Fe$
(b) $ZnSO_4+Fe$
(c) $MgSO_4+Pb$
(d) $CuSO_4+Fe$
Show Answer
Answer
(d) $CuSO_4+Fe$
Explanation
Iron is more reactive than copper hence it displaces copper in the reaction to form $Feso_4$.
36. Which one of the following figures correctly describes the process of electrolytic refining?
(a)
(b)
(c)
(d)
Show Answer
Answer
a)
Explanation
Copper ions are dispersed from positively charged anode and deposited on negatively charged cathode.
Short Answer Questions
37. 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.
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Answer
To identify the produced gas, lighted matchstick should be brought near the gas. If match stick burns with pop sound, it indicates the evolution of Hydrogen gas.
$M+2 NaOH \longrightarrow Na_2 MO_2+H_2$
With $HCl$
$M+2 HCl \longrightarrow MCl_2+H_2$
38. 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?
Show Answer
Answer
a) During extraction of metals, impure metal will be used as anode and pure metal is used as cathode for refining of silver metal by this electrolytic refining.
b) Silver Sulphate or Silver Nitrate
c) Pure silver is obtained on cathode
39. Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?
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Answer
Metal sulphides and carbonates are converted to metal oxides in the process of extraction of metal from them because metals can be obtained easier in oxide form than its sulphide or carbonate form.
40. Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with $HNO _3$, hydrogen is not liberated, why?
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Answer
$HNO _3$ is a strong oxidizing agent. It oxidises the liberated Hydrogen into water while converting itself to nitrogen oxide.
41. Compound $X$ and aluminium are used to join railway tracks. (a) Identify the compound $X$ (b) Name the reaction (c) Write down its reaction.
Show Answer
Answer
a) Answer is $Fe_2 O_3$
b) Involved reaction is a thermite reaction which is also called as aluminothermy c) $Fe 2 O 3(s)+2 Al(s) \to Al _2O _3(s)+2 Fe(s)+$ Heat Ferric oxide Aluminium Aluminium Iron Oxide.
42. When a metal $X$ is treated with cold water, it gives a basic salt $Y$ with molecular formula $X O H$ $($ Molecular mass $=40$ ) and liberates a gas $Z$ which easily catches fire. Identify $X, Y$ and $Z$ and also write the reaction involved.
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Answer
$X$ is $Na$ because molecular mass of $NaOH$ is 40 .
Hence $Y$ is $NaOH$
$Z$ is hydrogen has which catches fire when reacts with water.
$2 Na+2 H_2 O \longrightarrow 2 NaOH+H_2$
43. 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 $Z$.
Show Answer
Answer
$X$ is Carbon, $Y$ and $Z$ are Diamond and Graphite which are allotropes of the carbon.
44. The following reaction takes place when aluminium powder is heated with $MnO _2$
$3 MnO_2(s)+4 Al(s) \to 3 Mn$ (l) $+2 Al _2O _3$ (l) + Heat
(a) Is aluminium getting reduced? (b) Is $MnO _2$ getting oxidised?
Show Answer
Answer
In this reaction aluminium gets oxidized as oxygen gets combined with it. Since oxygen is removed from $MnO _2$ it is getting reduced.
45. What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?
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Answer
Solder alloy is made of Lead and aluminium. Its low melting point makes it suitable for welding electrical wires.
46. 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 $NaOH$.
Show Answer
Answer
Metal A is Aluminium and $B$ is $Al _2O _3$
With HCl
$Al_2 O_3+6 HCl \longrightarrow 2 AlCl_3+3 H_2 O$
With $NaOH$
$Al_2 O_3+2 NaOH \longrightarrow 2 NaAlO _2+H _2O$
47. A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.
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Answer
Mercury is the metal which is liquid at room temperature. Ore of Mercury is Cinnabar. When we heat cinnabar in atmospheric oxygen following reaction takes place.
$2 HgS+3 O_2 \to 2 HgO+2 SO_2$
Mercuric oxide is again heated to get Mercury and Oxygen
$2 HgO \xrightarrow{\text{Heat}} Hg+O_2$
48. Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements.
(a) Mg and N2
(b) $Li$ and $O _2$
(c) $Al$ and $Cl _2$
(d) $K$ and $O _2$
Show Answer
Answer
a) Magnessium Nitride $(Mg_3 N_2)$
b) Lithium Oxide $(Li_2 O)$
c) Aluminium Chloride $(AlCl_3)$
d) Potassium Oxide $(K_2 O)$
49. What happens when
(a) $ZnCO3$ is heated in the absence of oxygen?
(b) a mixture of $Cu _2 O$ and $Cu _2 S$ is heated?
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Answer
a) When $ZnCO _3$ is heated in the absence of oxygen Zinc Oxide and Carbon-di-oxide are liberated.
$ZnCO_3 \longrightarrow ZNO+CO_2$
b) When a mixture of $Cu _2 O$ and $Cu _2 S$ is heated we get pure copper
$2 Cu _2 O+Cu _2 S \longrightarrow 6 Cu+SO_2$
50. A non-metal $A$ is an important constituent of our food and forms two oxides $B$ and $C$. Oxide $B$ is toxic whereas $C$ causes global warming
(a) Identify A, B and C
(b) To which Group of Periodic Table does A belong?
Show Answer
Answer
a) A is Carbon. B is Carbon monoxide C is Carbon-dioxide
b) Group 14
51. Give two examples each of the metals that are good conductors and poor conductors of heat respectively.
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Answer
Good conductors- Iron and Copper
Bad conductors- Lead and Mercury
52. Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than $310 K(37^{\circ} C)$
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Answer
Mercury and Bromine are liquid at room temperature. Caesium and Gallium are the metals whose melting point is less than $310 K(37^{\circ} C)$.
53. 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.
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Answer
A is calcium, B is calcium Hydroxide and C is Calcium Oxide.
$Ca+2 H_2 O \longrightarrow Ca(OH)_2+H_2$
$Ca(OH)_2 \longrightarrow CaO+H_2 O$
$CaO+H_2 O \longrightarrow Ca(OH)_2$
54. An alkali metal A gives a compound $B$ (molecular mass $=40$ ) on reacting with water. The compound $B$ gives a soluble compound $C$ on treatment with aluminium oxide. Identify $A, B$ and $C$ and give the reaction involved.
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Answer
A is sodium and B is Sodium Hydroxide. Because molecular mass of $NaOH$ is 40 . So C is Sodium Aluminate.
$Al_2 O_3+2 NaOH \longrightarrow 2 NaAlO_2+H_2 O$
55. Give the reaction involved during extraction of zinc from its ore by (a) roasting of zinc ore (b) calcination of zinc ore
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Answer
a) $2 ZnS+3 O_2 \to 2 ZnO+2 SO_2$.
b) $ZnCO_3 \to ZnO+CO$
56. A metal $M$ does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify $M$ and black coloured product and also explain the reaction of $M$ with oxygen.
Show Answer
Answer
Copper is the metal which does not react with acids. With oxygen it forms Copper Oxide.
Metal M is Copper and black colored product is Copper oxide.
$2 Cu+O_2 \longrightarrow 2 CuO$
57. An element forms an oxide A2O3 which is acidic in nature. Identify A as a metal or non-metal.
Show Answer
Answer
A is a non-metal because oxides of non-metals are acidic in nature.
58. A solution of $CuSO _4$ was kept in an iron pot. After few days the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.
Show Answer
Answer
Iron is more reactive than copper hence Iron displaces Copper to produce $FeSO_4$. In this process a portion of Iron Gets dissolved which results in Holes in the pot.
$Fe+CuSO_4 \longrightarrow FeSO_4+Cu$
Long Answer Questions
59. 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?
Show Answer
Answer
a)
Non-metal a is nitrogen because it is the largest constituent of air which constitute around 78% of the gases.. B is Ammonia, C is Nitrogen-di-oxide and D is Nitric acid.
When heated with $H _2$ in 1:3 ratio in the presence of catalyst $(Fe)$ following reaction takes place.
$3 N_2+3 H_2 \longrightarrow 2 NH_3$
On heating Nitrogen with $O _2$ it gives nitrogen-di-oxide
$N_2+3 O \longrightarrow 2 NO_2$
When nitrogen-di-oxide is passed into water in the presence of air it gives an Nitric acid
$NO_2+H_2 O \longrightarrow HNO_3$
b) Nitrogen belong to group 15
60. Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.
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Answer
During the extraction of metals of low and medium reactivity from their respective sulphide ores. They are first heated in presence of atmospheric oxygen. This step will give out oxides of metal. This step is used as it is more efficient method to extract methods.
Ex: Cinnabar is heated in air to get mercuric sulphide oxidize to produce mercuric oxide.
$2 HgS+3 O_2 \to 2 HgO+2 SO_2$
Mercuric oxide is further heat to get Mercury
$2 HgO \longrightarrow 2 Hg+O_2$
Zinc is a metal of medium reactivity and its ore is Zinc Blende
Zinc Blend is roasted to get Zinc oxide
$2 ZnS+3 O_2 \longrightarrow 2 ZnO+2 SO_2$
$ZNCO_3 \longrightarrow ZnO+CO_2$
Zinc oxide when heated wit $CO_2$ Zinc is obtained
$ZnO+C \longrightarrow Zn+CO$
61. Explain the following
(a) Reactivity of $Al$ decreases if it is dipped in $HNO _3$
(b) Carbon cannot reduce the oxides of $Na$ or $Mg$
(c) $NaCl$ is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state
(d) Iron articles are galvanised.
(e) Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.
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Answer
a) Reactivity of Aluminium decreases if it is dipped in $HNO_3$ because $HNO_3$ is a strong oxidizing agent. Here a layer a layer of aluminium oxide gets deposited because of which reactivity of alumnium gets reduced.
(b) Carbon cannot reduce the oxides of Na or Mg because these are highly reactive metals. Na and Mg have higher affinity to oxygen than carbon. Hence carbon fails to reduce the oxides of Na and Mg.
(c) $NaCl$ is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state because $NaCl$ is an ionic compound. Ionic compounds cannot conduct electricity in solid state but they can conduct electricity in aqueous solution and in molten state. d) Iron readily reacts with atmospheric oxygen and forms rust. To avoid rusting of iron it is galvanized.
e) Metals like Na, K, Ca and Mg are are highly reactive metals. They can form compounds with almost every element . Because of this they are not found in their native form in nature.
62. (i) Given below are the steps for extraction of copper from its ore. Write the reaction involved.
(a) Roasting of copper (1) sulphide
(b) Reduction of copper (1) oxide with copper (1) sulphide.
(c) Electrolytic refining
(ii) Draw a neat and well labelled diagram for electrolytic refining of copper
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Answer
a) $2 Cu_2 S+3 O_2 \longrightarrow 2 Cu_2 O+SO_2$
b) $2 Cu_2 O+Cu_2 S \longrightarrow 6 Cu+SO_2$
c) $Cu^{2+} + 2 e^{-} \longrightarrow Cu$
63. Of the three metals $X, Y$ and $Z$. $X$ reacts with cold water, $Y$ with hot water and $Z$ with steam only. Identify $X, Y$ and $Z$ and also arrange them in order of increasing reactivity.
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Answer
$X$ reacts with cold water.
Hence, the element should be Sodium
$Ca+H_2 O \longrightarrow Ca(OH)_2+H_2$
Y reacts with hotwater, Hence, it is “Magnesium”
$Mg+H_2 O \longrightarrow Mg(OH)_2+H_2$
$Z$ reacts with steam only. Hence, it is Iron
$Fe+H_2 O \longrightarrow Fe_2 O_3+H_2$
Arranging in ascending order (increasing order of reactivity)
$Fe<Mg<Ca$
64. An element $A$ burns with golden flame in air. It reacts with another element $B$, atomic number 17 to give a product $C$. An aqueous solution of product $C$ on electrolysis gives a compound $D$ and liberates hydrogen. Identify A, B, C and D. Also write down the equations for the reactions involved.
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Answer
Element A is 17 Sodium because it will burn with golden flame in air.
Element B is Chlorine for its atomic number is 17.
Product C is Sodium Chloride
$2 Na+CL_2 \longrightarrow 2 NaCl$
Product D is Sodium hydroxide
$2 NaCl+2 H_2 O \quad 2 NaOH+Cl_2+H_2$
65. Two ores A and B were taken. On heating ore A gives $CO _2$ whereas, ore $B$ gives $SO _2$. What steps will you take to convert them into metals?
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Answer
Ore A gives $CO_2$ on heating hence it is a carbonate ore
Steps involved in Extraction of ore A
a) Calcination
Ore is heated in limited supply of air to obtain metal oxide
$ACO _3 \longrightarrow AO+CO _2$
b) Reduction
Metal oxide is reduced with coke to obtain metal.
$AO+C \longrightarrow A+CO$
Ore B is a sulphide ore
Steps involved in extraction of element B are
a) Roasting
Ore is heated in presence of air to obtain metal oxide
$2 BS+3 O_2 \longrightarrow 2 BO+2 SO_2$
b) Reduction
Metal oxide is reduced to metal by carbon
$BO+C \longrightarrow B+CO$
