Intext Questions

Q.1 Take samples of iron, copper, aluminium and magnesium. Note the appearance of each sample.

Sol. They appear a little shiny.

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Q.2 Clean the surface of each sample by rubbing them with sand paper and note their appearance again.

Sol. They appear very shiny.

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Page No. 40

Q.1 Give an example of a metal which

(i) is a liquid at room temperature;

(ii) can be easily cut with a knife;

(iii) is the best conductor of heat;

(iv) is a poor conductor of heat.
Sol.

(i) Mercury,

(ii) Sodium,

(iii) Silver,

(iv) Astatine is the poorest conductor of heat among all metals. Its conductivity is less than even some non-metals like graphite.

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Q.2 Explain the meanings of malleable and ductile.
Sol.

Malleable : Some metals can be beaten into thin sheets. This property is called malleability.

Ductile : The ability of metals to be drawn into thin wires is called ductility.

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Page No. 46

Q.1 Why is sodium kept immersed in kerosene oil ?
Sol.

Sodium reacts with oxygen and moisture at room temperature. But, it neither react nor dissolve in kerosene. So, sodium is kept under kerosene.

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Q.2 Write equations for the reactions of

(i) iron with steam;

(ii) calcium and potassium with water.
Sol.

(i) 2Fe+3H2O→Fe2O3+3H2

(ii) Ca+2H2O→Ca(OH)2+H2

2K+2H2O→2KOH+H2+Heatenergy

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Q.3 Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows :

Use the table above to answer the following questions about metals A, B, C and D.

(i) Which s the most reactive metal ?

(ii) What would you observe if B is added to a solution of Copper (II) sulphate ?

(iii) Arrange the metals A, B, C and D in the order of reactivity.
Sol.

(i) Metals B is most reactive.

(ii) Displacement reaction.

(iii) Metal B > Metal A > Metal C > Metal D

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Q.4  Which gas is produced when dilute hydrochloric acid is added to a reactive metal ? Write the chemical reaction when iron reacts with dilute H₂SO₄.
Sol.

Hydrogen gas is evolved along with salt of the metal.

Fe+H2CO4→FeSO4+H2

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Q.5 What would you observe when zinc is added to a solution of iron (II) sulphate ? Write the chemical reaction that takes place.
Sol.

Zinc will displace iron from iron (II) sulphate.

Zn+FeSO4→ZnSO4+Fe

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Page No. 49

Q.1 (i) Write the electron-dot structures for sodium, oxygen and magnesium.

(ii) Show the formation of Na₂O and MgO by the transfer of electrons.

(iii) What are the ions present in these compounds ?
Sol.

(i)

(ii)

(iii) Na2O→Na+ and O2−

MgO→Mg2+ and O2−

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Q.2 Why do ionic compounds have high melting points ?

Sol. The molecules of ionic compounds are bounded by strong electrostatic force.

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Page No. 53

Q.1 Define the following terms :

(i) Mineral  (ii) Ore  (iii) Gangue
Sol.

(i) Mineral : The elements or compounds which occur naturally in the earth’s crust are known as minerals.

(ii) Ore : At some places, minerals contain a very high percentage of a particular metal and the metal can be percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.

(iii) Gangue : Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.

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Q.2 Name two metals which are found in nature in the free state.

Sol. Gold, platinum.

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Q.3 What chemical process is used for obtaining a metal from its oxide ?

Sol. Reduction by carbon.

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Page No. 55

Q.1 Metallic oxides of zinc, magnesium and copper were beated with the following metals :

In which cases will you find displacement reactions taking place ?
Sol.

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Q.2 Which metals do not corrode easily ?

Sol. Metals low in activity series, like gold, silver, etc. do not corrode easily.

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Q.3 What are alloys ?

Sol. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Exercise

Q.1 Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.

Sol.    (d) AgNO₃ solution and copper metal.

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Q.2  Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.

Sol.     (c) Applying a coating of zinc.

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Q.3 An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron.

Sol.     (a) Calcium

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Q.4 Food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin.
(b) zinc has a higher melting point than tin.
(c) zinc is more reactive than tin.
(d) zinc is less reactive than tin.

Sol.      (c) zinc is more reactive than tin.

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Q.5  You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Sol.      

(a) We will make a circuit as shown in the figure :

If with the test material, the bulb glows on turning the switch on, the material is likely to be a metal.

(b) The method is pretty useful except for graphite which is a good conductor of electricity although it is a non-metal.

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Q.6 What are amphoteric oxides ? Give two examples of amphoteric oxides.
Sol.

The oxides which react with both acids and bases to give salt are called amphoteric oxide.

For example, aluminium oxide reacts in the following manner with acids and bases :

Al2O3+6HCl→2AlCl3+3H2O

Al2O3+2NaOH→2NaIO2+H2O

Other amphoteric oxides are, zinc oxide, bad oxide.

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Q.7 Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Sol.

Metals that displace hydrogen : Magnesium, zinc. Metals that do not displace hydrogen : Copper, gold.

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Q.8 In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte ?
Sol.

In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. The apparatus is set up as shown in figure. On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas the insoluble impurities settle down at the bottom of the anode and are known as anode mud.

Electrolytic refining of copper. The electrolyte is a solution of acidified copper sulphate.
The anode is impure copper, whereas the cathode is a strip of pure copper.
On passing electric current pure copper is deposited on the cathode.

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Q.9 Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in the figure.

(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.
Sol.

(a) (i) No Effect on dry litmus paper.

(ii) Turns blue litmus red in moist state.

(b) S+O2→SO2

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Q.10 State two ways to prevent the rusting of iron.
Sol.

(i) Galvanisation : In this method, a coating of zinc is given on the iron article.

(ii) Painting : In this method, a coating of paint is given on the iron article.

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Q.11 What type of oxides are formed when non-metals combine with oxygen ?

Sol.   Basic and amphoteric.

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Q.12 Give reasons :

(a) Platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium and lithium are stored under oil.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Sol.

(a) Platinum, gold and silver are very less reactive and do not corrode. They also possess very brilliant lustre. So, they are used in jewellery.

(b) Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.

(c) Aluminium does not corrode and is a very good conductor of heat.

(d) It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonaties. Therefore, prior to reduction, the metal sulphides and carbonates must be converted into metal oxides.

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Q.13 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.
Sol.

Copper oxide reacts with acids but copper itself does not react. So, the copper can be washed by acidic substances. It removes the corroded part (copper oxide) and pure copper is left behind.

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Q.14 Differentiate between metal and non-metal on the basis of their chemical properties.
Sol.

(i) Ion formation : Metals from positive ions and non-metals from negative ions.

(ii) Acidic nature : Metals form basic oxides and non-metals form acidic oxide.

(iii) Reaction with water : Metals react with water but non-metals do not.

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Q.15 A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold bangles to him which he dipped in a particular solution. The 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 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 ?

Sol.  The solution the used was aqua regia.

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Q.16 Give the reason why copper is used to make hot water tanks but steel (an alloy of iron) is not.
Sol.

Hot iron reacts with steam formed by boiling water. But, copper does not react with water.

Exemplar

Multiple Choice Questions : 

Q.1 Which of the following property is generally not shown by metals?

(a) Electrical conduction

(b) Sonorous in nature

(c) Dullness

(d) Ductility

Sol. (c)

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Q.2 The ability of metals to be drawn into thin wire is known as

(a) Ductility

(b) Malleability

(c) Sonorousity

(d) Conductivity

Sol. (a)

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Q.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)

Sol. (d)

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Q.4 Which one of the following metals does not react with cold as well as hot water?

(a) Na

(b) Ca

(c) Mg

(d) Fe

Sol. (d)

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Q.5 Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?

(a) FeO

(b) Fe₂O₃

(c) Fe₃O₄

(d) Fe₂O₃ and Fe₃O₄

Sol. (c)

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Q.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)

Sol. (d)

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Q.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) H₂SO₄

(b) HCl

(c) HNO₃

(d) All of these

Sol. (c)

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Q.8 The composition of aqua-regia is

(a) Dil.HCl : Conc. HNO₃ − 3 : 1

(b) Conc.HCl : Dil. HNO₃− 3 : 1

(c) Conc.HCl : Conc.HNO₃− 3 : 1

(d) Dil.HCl : Dil.HNO₃− 3 : 1

Sol. (c)

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Q.9 Which of the following are not ionic compounds?

(i) KCl

(ii) HCl

(iii) CCl₄

(iv) NaCl

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iii)

Sol. (b)

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Q.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

Sol. (b)

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Q.11 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)

Sol. (a)

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Q.12 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)

Sol. (d)

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Q.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

Sol. (c)

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Q.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

Sol. (c)

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Q.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

Sol. (a)

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Q.16 If copper is kept in open 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

Sol. (d)

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Q.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

Sol. (d)

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Q.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)

Sol. (d)

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Q.19 Generally, non-metals are not lustrous. Which of the following non-metal is lustrous?

(a) Sulphur

(b) Oxygen

(c) Nitrogen

(d) Iodine

Sol. (d)

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Q.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

Sol. (b)

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Q.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

Sol. (b)

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Q.22 An alloy is

(a) an element

(b) a compound

(c) a homogeneous mixture

(d) a heterogeneous mixture

Sol. (c)

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Q.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)

Sol. (b)

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Q.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

Sol. (a)

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Q.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

Sol. (b)

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Q.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

Sol. (d)

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Q.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

Sol. (b)

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Q.28 Which among the following alloys contain mercury as one of its constituents?

(a) Stainless steel

(b) Alnico

(c) Solder

(d) Zinc amalgam

Sol. (d)

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Q.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

Sol. (b)

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Q.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

Sol. (d)

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Q.31 Although metals form basic oxides, which of the following metals form an amphoteric oxide?

(a) Na

(b) Ca

(c) Al

(d) Cu

Sol. (c)

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Q.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

Sol. (b)

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Q.33 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

Sol. (c)

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Q.34 Which of the following non-metals is a liquid?

(a) Carbon

(b) Bromine

(c) Phosphorus

(d) Sulphur

Sol. (b)

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Q.35 Which of the following can undergo a chemical reaction?

(a) MgSO₄ + Fe

(b) ZnSO₄ + Fe

(c) MgSO₄ + Pb

(d) CuSO₄ + Fe

Sol. (d)

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Q.36 Which one of the following figures correctly describes the process of electrolytic refining?

Sol. (c)