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Metals and Non-Metals : NCERT Intext Questions


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Page No. 37

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

Sol. They appear a little shiny.


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

Sol. They appear very shiny.


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.


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.


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.


Q.2 Write equations for the reactions of

(i) iron with steam;

(ii) calcium and potassium with water.
Sol.

(i) 2Fe + 3{H_2}O \to F{e_2}{O_3} + 3{H_2}

(ii) Ca + 2{H_2}O \to Ca{\left( {OH} \right)_2} + {H_2}

2K + 2{H_2}O \to 2KOH + {H_2} + Heat\,\,energy


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


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 + {H_2}C{O_4} \to FeS{O_4} + {H_2}


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 + FeS{O_4} \to ZnS{O_4} + Fe


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) N{a_2}O \to N{a^ + } and {O^{2 - }}

MgO \to M{g^{2 + }} and {O^{2 - }}


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

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


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.


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

Sol. Gold, platinum.


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

Sol. Reduction by carbon.


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.


Q.2 Which metals do not corrode easily ?

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


Q.3 What are alloys ?

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



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