Lesson:Metals and NON-METALS Physical Properties of metals and non-metals (See)

Question 1

Which of the following pairs will give displacement reactions?

(a) $N a C l$ solution and copper metal

(b) $M g C l_{2}$ solution and aluminium metal

(d) $A g N O_{3}$ solution and copper metal.

Solution:

(d)

Question 2

Which of the following methods is suitable for preventing an iron frying pan from rusting?

(a) Applying grease

(b) Applying paint

(d) All of the above.

Solution:

(c)

Question 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

(d) Iron.

Solution:

(a)

Question 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.

(d) Zinc is less reactive than tin.

Solution:

(c)

Question 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.

Solution:

(a) If the given sample can be beaten into thin sheets by the hammer, then it is a metal, otherwise it is a non-metal.

Similarly, if a circuit made by the given sample, the battery, the bulb, the wires and the switch conducts electricity, then it is a metal. Otherwise the sample is a non-metal.

(b) The above tests are useful as they help in distinguishing between metals and non-metals without involving any chemical reaction.

Question 6

What are amphoteric oxides? Give two examples of amphoteric oxides.

Solution:

The oxides which behave both as acidic as well as basic in nature are called amphoteric oxides.

Examples: aluminium oxide ( $A l_{2} O_{3}$ ), zinc oxide ( $Z n O$ )

Question 7

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

Solution:

Sodium and aluminium will displace hydrogen from dilute acids.

Mercury and copper cannot displace hydrogen from dilute acids.

Question 8

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

Solution:

In the electrolytic refining of a metal M:

· The anode is the impure metal M

· The cathode is the thin strip of pure metal M

· The electrolyte is the solution of the salt of the metal M

Question 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 figure below.

(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.

Solution:

(a) (i) There will be no action on the dry litmus paper.

(ii) The colour of the moist litmus paper turns red as sulphur is a non-metal and the oxides of non-metals are acidic in nature.

(b) $S (s) + O_{2} (g) \to S O_{2} (g)$

Question 10

State two ways to prevent the rusting of iron.

Solution:

Two ways to prevent the rusting of iron are:

(i) Application of oil or paint

(ii) Galvanisation

Question 11

What types of oxides are formed when non-metals combine with oxygen?

Solution:

Neutral or acidic oxides are formed when non-metals combine with oxygen. Examples are $N O_{2}$ and $S O_{2}$ are neutral oxides.

Question 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.

Solution:

(a) Platinum, gold and silver are used to make jewellery because they are very lustrous, less reactive and do not corrode easily.

(b) Sodium, potassium and lithium, being highly reactive, are stored under oil to prevent their reaction with air and moisture.

(c) Aluminium is light in weight and is a good conductor of heat. It reacts with oxygen present in the air to form a thin layer of aluminium oxide. This oxide layer is very stable. It prevents further reaction of aluminium with oxygen.

So, even though 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. This is due to the fact that metals can be more easily extracted from their oxides rather than from their carbonates and sulphides.

Question 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.

Solution:

Copper reacts with carbon dioxide in the air to form copper carbonate. Due to this, it loses its shiny brown surface and a green coating of copper carbonate is formed. The citric acid present in the lemon or tamarind neutralises the copper carbonate, thereby dissolving the layer and thus helping in cleaning the vessel.

Question 14

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

Solution:

Metals	Non-metals
Metals form basic oxides on reaction with oxygen.	Non-metals form acidic oxides or neutral oxides on reaction with oxygen.
Some metals displace hydrogen from water.	Non-metals do not react with water to evolve hydrogen.
Metals usually displace hydrogen from dilute acids.	Non-metals do not react with dilute acids.

Question 15

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?

Solution:

The solution he had used was Aqua regia. It is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1. When a gold ornament is cleaned with Aqua regia, some of the gold gets dissolved in it. This results in the loss in weight of the gold ornament.

Question 16

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Solution:

Copper does not react with any form of water, be it cold, hot or steam. On the other hand, steel (an alloy of iron) reacts with steam to form iron oxide. Due to this reason, copper is used to make hot water tanks, and not steel.

Lesson: Metals and Non-metals

Question 1

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

(a) Electrical conduction

(b) Sonorous in nature

(d) Ductility

Solution:

(c)

Question 2

The ability of metals to be drawn into thin wire is known as:

(a) Ductility

(b) Malleability

(d) Conductivity

Solution:

(a)

Question 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)

(d) (i) and (iv)

Solution:

(d)

Question 4

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

(a) Na

(b) Ca

(d) Fe

Solution:

(d)

Question 5

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

(a) $F e O$

(b) $F e_{2} O_{3}$

(d) $F e_{2} O_{3} a n d F e_{3} O_{4}$

Solution:

(c)

Question 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)

(d) (iii) and (iv)

Solution:

(d)

Question 7

Generally, metals react with acids to give salt and hydrogen gas.

Which one of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg)?

(a) $H_{2} S O_{4}$

(b) $H C l$

(d) All of these

Solution:

(c)

Question 8

The composition of aqua-regia is:

(a) $D i l . H C l : C o n c . H N O_{3}$

$3 : 1$

(b) $C o n c . H C l : D i l . H N O_{3}$

$3 : 1$

(d) $D i l . H C l : D i l . H N O_{3}$

$3 : 1$

Solution:

(c)

Question 9

Which of the following are not ionic compounds?

(i) $K C l$

(ii) $H C l$

(iii) $C C l_{4}$

(iv) $N a C l$

(a) (i) and (ii)

(b) (ii) and (iii)

(d) (i) and (iii)

Solution:

(b)

Question 10

Which one of the following properties is not generally exhibited by ionic compounds?

(a) Solubility in water

(b) Electrical conductivity in solid state

(d) Electrical conductivity in molten state

Solution:

(b):

Question 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)

(d) (iii) and (iv)

Solution:

(c)

Question 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)

(d) (iii) and (iv)

Solution:

(a)

Question 13

Silver articles become black on prolonged exposure to air. This is due to the formation of:

(a) $A g_{3} N$

(b) $A g_{2} O$

(d) $A g_{2} S a n d A g_{3} N$

Solution:

(c)

Question 14

Galvanisation is a method of protecting iron from rusting by coating with a thin layer of:

(a) Gallium

(b) Aluminium

(d) Silver

Solution:

(c)

Question 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

(d) Cu and Au

Solution:

(a)

Question 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) $C u S O_{4}$

(b) $C u C O_{3}$

(d) $C u O$

Solution:

(b)

Question 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

(d) Hg

Solution:

(d)

Question 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)

(d) (i) and (ii)

Solution:

(d)

Question 19

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

(a) Sulphur

(b) Oxygen

(d) Iodine

Solution:

(d)

Question 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

(d) Cu

Solution:

(b)

Question 21

2 mL each of concentrated $H C l$ , $H N O_{3}$ and a mixture of concentrated

$H C l$ and concentrated $H N O_{3}$ 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

(d) Pt

Solution:

(b)

Question 22

An alloy is:

(a) An element

(b) A compound

(d) A heterogeneous mixture

Solution:

(c)

Question 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)

(d) (ii) ad (iv)

Solution:

(b)

Question 24

During electrolytic refining of zinc, it gets:

(a) Deposited on cathode

(b) Deposited on anode

(d) Remains in the solution

Solution:

(a)

Question 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

(d) Ca

Solution:

(b)

Question 26

Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?

(a) Brass

(b) Bronze

(d) Steel

Solution:

(d)

Question 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

(d) It reacts with steam to form magnesium hydroxide and evolves hydrogen gas

Solution:

(b)

Question 28

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

(a) Stainless steel

(b) Alnico

(d) Zinc amalgam

Solution:

(d)

Question 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

(d) Occurs as solid

Solution:

(b)

Question 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

(d) Y is a non-metal and Z is a metal

Solution:

(d)

Question 31

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

(a) Na

(b) Ca

(d) Cu

Solution:

(c)

Question 32

Generally, non-metals are not conductors of electricity. Which of the following is a good conductor of electricity?

(a) Diamond

(b) Graphite

(d) Fullerene

Solution:

(b)

Question 33

Electrical wires have a coating of an insulting material. The material, generally used is:

(a) Sulphur

(b) Graphite

(d) All can be used

Solution:

(c)

Question 34

Which of the following non-metals is a liquid?

(a) Carbon

(b) Bromine

(d) Sulphur

Solution:

(b)

Question 35

Which of the following can undergo a chemical reaction?

(a) $M g S O_{4} + F e$

(b $Z n S O_{4} + F e$

(d) $C u S O_{4} + F e$

Solution:

(d)

Question 36

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

Solution:

(c)

Question 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 he can identify the produced gas? Write chemical equations for both the reactions.

Solution:

The produced gas can be identified by bringing a burning candle near the mouth of the reaction vessel. The gas burns with a pop sound. Hence, it is hydrogen.

$\begin{array}{l} M + 2 N a O H \to N a_{2} M O_{2} + H_{2} \\ M + 2 H C l \to M C l_{2} + H_{2} \end{array}$

Question 38

During extraction of metals, electrolytic 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.

Solution:

(a) Impure silver will be used as anode whereas pure silver will be used as cathode.

(b) Silver salt, such as $A g N O_{3}$ can be used as the electrolyte.

Question 39

Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?

Solution:

Compared to the metal sulphides and carbonates, it is easier to obtain the metal from its oxide. Hence, in the process of extraction of metal, the metal sulphides and carbonates should be converted to metal oxides.

Question 40

Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with $H N O_{3}$ , hydrogen is not liberated, why?

Solution:

It is because $H N O_{3}$ is a strong oxidising agent. Hence, it oxidises the hydrogen

( $H_{2}$ ) and produces $H_{2} O$ .

Question 41

Compound X and aluminium are used to join railway tracks.

(a) Identify the compound X

(b) Name the reaction

Solution:

Question 42

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula $X O H (M o l e c u l a r m a s s = 40)$ and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

Solution:

$\begin{array}{l} X — N a \\ Y — N a O H \\ Z — H_{2} \end{array}$

$Y — N a O H$

$Z — H_{2}$

Reaction involved

. $2 N a + 2 H_{2} O \to 2 N a O H + H_{2} + H e a t e n e r g y$ .

Question 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.

Solution:

X $—$ Carbon

Y $—$ Diamond

Z $—$ Graphite

Question 44

The following reaction takes place when aluminium powder is heated with $M n O_{2}$

$3 {MnO}_{2} (s) +4 Al (s) \to 3 Mn (l) +2 {Al}_{2} O_{3} (l) +Heat$

(a) Is aluminium getting reduced?

(b) Is $M n O_{2}$ getting oxidised?

Solution:

(a) No. In the given reaction, oxygen is added to aluminium. Therefore, aluminium is getting oxidized.

(b) No. In the given reaction, manganese loses oxygen. Therefore, manganese is reduced, not oxidised.

Question 45

What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?

Solution:

The constituents of solder alloy are lead and tin. The property of solder that makes it suitable for welding electrical wires is its low melting point.

Question 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 $H C l$ and $N a O H$ .

Solution:

$\begin{array}{l} A — A l \\ B — A l_{2} O_{3} \\ A l_{2} O_{3} + 6 H C l \to 2 A l C l_{3} + 3 H_{2} O \\ A l_{2} O_{3} + 2 N a O H \to 2 N a A l O_{2} + H_{2} O \end{array}$

Question 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.

Solution:

The metal is mercury. It is liquid at room temperature. It can be obtained by heating its ore, cinnabar (HgS) in air to convert it into mercury oxide. The oxide is then reduced to mercury by further heating.

The reactions are as follows:

$\begin{array}{l} 2 H g S + 3 O_{2} \overset{H e a t}{\to} 2 H g O + 2 S O_{2} \\ 2 H g O \overset{H e a t}{\to} 2 H g + O_{2} \end{array}$

Question 48

Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements.

M g a n d N_{2}

Solution:

Question 49

$2 C u_{2} O + C u_{2} S \overset{H e a t}{\to} 6 C u + S O_{2}$

Question 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?

Solution:

(a) A is carbon, B is carbon monoxide and C is carbon dioxide.

(b) A belongs to Group $-$ 14 of the periodic table.

Question 51

Give two examples each of the metals that are good conductors and poor conductors of heat respectively.

Solution:

(a) The metals which are good conductors of heat and electricity are silver (Ag) and copper (Cu).

(b) The metals which are poor conductors of heat and electricity are lead (Pb) and mercury (Hg).

Question 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 $310 K (37 ° C)$ .

Solution:

Metal $-$ mercury (Hg)

Non-metal $-$ bromine (Br)

Two metals with melting point less than 310 K are caesium (Cs) and gallium (Ga)

Question 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, Band C and give the reactions involved.

Solution:

$\begin{array}{l} A — C a \\ B — C a {(O H)}_{2} \\ C — C a O \\ C a (s) + 2 H_{2} O \to C a {(O H)}_{2} (a q) + H_{2} (g) \\ C a {(O H)}_{2} \overset{H e a t}{\to} C a O + H_{2} O \end{array}$

Question 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.

Solution:

$\begin{array}{l} A — N a \\ B — N a O H \\ C — N a A l O_{2} \end{array}$

$\begin{array}{l} 2 N a + 2 H_{2} O \to 2 N a O H + H_{2} \\ A l_{2} O_{3} + 2 N a O H \to 2 N a A l O_{2} + H_{2} O \end{array}$

Question 55

Give the reaction involved during extraction of zinc from its ore by

(a) Roasting of zinc ore

(b) Calcination of zinc ore

Solution:

Question 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.

Solution:

The metal M is copper (Cu) which is less reactive and does not liberate hydrogen from acids.

Copper reacts with oxygen and forms a black coloured product, copper(II) oxide (CuO).

Reaction involved: $2 C u + O_{2} \to 2 C u O$

Question 57

An element forms an oxide $A_{2} O_{3}$ which is acidic in nature. Identify A as a metal or non-metal.

Solution:

Since the oxide of the element is acidic in nature, A is a non-metal.

Question 58

A solution of $C u S O_{4}$ 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.

Solution:

Since iron ( $F e$ )is more reactive than copper ( $C u$ ), it displaces copper from copper sulphate solution ( $C u S O_{4}$ ) and forms iron sulphate ( $F e S O_{4}$ ). This reaction results in the formation of holes in the iron pot.

The equation of the reaction is as follows:

$F e + C u S O_{4} \to F e S O_{4} + C u$

Question 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 ( $F e$ ) 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?

Solution:

$B — N H_{3}$

$C — N O$

$D — H N O_{3}$

Question 60

Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

Solution:

Question 61

Explain the following:

(a) Reactivity of Al decreases if it is dipped in $H N O_{3}$

(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.

Solution:

a) Due to the formation of an oxide layer i.e., $A l_{2} O_{3}$ , the reactivity of Al decreases.

(b) Compared to carbon (C), sodium (Na) and magnesium (Mg) are more reactive metals. Hence, carbon cannot reduce the oxides of Na or Mg.

(c) Due to its rigid structure, the movement of ions is not possible in solid NaCl. Hence it is not a conductor of electricity in the solid state. But in an aqueous solution or in molten state, the ions can move freely. Hence, it conducts electricity.

(d) Iron articles are galvanised to protect them from corrosion.

(e) Na, K, Ca and Mg are highly reactive. Hence, they are never found in their free states in nature.

Question 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.

(ii) Draw a neat and well labelled diagram for electrolytic refining of copper

Solution:

Question 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.

Solution:

· X is a metal alkali. It can be either sodium or potassium.

· Y is an alkaline metal. It can be either magnesium or calcium.

· The metal which reacts with steam only is iron.

The increasing reactivity series of the metals are $N a > M g > F e$ .

Question 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.

Solution:

$\begin{array}{l} A=Na \\ B = C l_{2} \\ C = N a C l \\ D = N a O H \end{array}$

Question 65

Two ores A and B were taken. On heating, ore A gives $C O_{2}$ whereas, ore B gives $S O_{2}$ . What steps will you take to convert them into metals?

Solution:

On heating, ore A gives $C O_{2}$ and ore B gives $S O_{2}$ . Therefore, the ores are $M C O_{3}$ and MS.

Lesson: Metals and Non-metals

Question 1

Give an example of a metal which

(a) is a liquid at room temperature.

(b) can be easily cut with a knife.

(d) is a poor conductor of heat.

Solution:

(a) Mercury

(b) Sodium

(d) Mercury and lead

Question 2

Explain the meanings of malleable and ductile.

Solution:

A substance is said to be malleable if it can be beaten into thin sheets.

A substance is said to be ductile if it can be drawn into thin wires.

Generally metals are both ductile and malleable.

Question 3

Why sodium is kept immersed in kerosene oil?

Solution:

Sodium is a highly reactive element. It is kept immersed in kerosene oil to avoid its reaction with oxygen. Such reactions are also explosive in nature.

Keeping sodium immersed in kerosene helps:

a) preventing accidental damage.

b) storing sodium in its pure form.

Question 4

Write equations for the reactions of:

(i) Iron with steam

(ii) Calcium and potassium with water

Solution:

(i) $3 F e (s) + 4 H_{2} O (g) \to F e_{3} O_{4} (a q) + 4 H_{2} (g)$

(ii) $C a (s) + 2 H_{2} O (l) \to C a {(O H)}_{2} (a q) + H_{2} (g) + H e a t$

$2 K (s) + 2 H_{2} O (l) \to 2 K O H (a q) + H_{2} (g) + H e a t$

Question 5

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.

Metal

Iron (II) Sulphate

Copper (II) Sulphate

Zinc Sulphate

Silver nitrate

No reaction

Displacement

No reaction

Displacement

No reaction

Displacement

No reaction

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

(i) Which is 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 decreasing reactivity.

Solution:

(i) B is the most reactive metal.

(ii) B will displace copper from the copper sulphate solution.

(iii) Arrangement of metals in the order of decreasing reactivity: $B > A > C > D .$

Question 6

Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute $H_{2} S O_{4}$ .

Solution:

When a reactive metal reacts with dilute hydrochloric acid, hydrogen gas is produced.

The chemical reaction when iron reacts with dilute $H_{2} S O_{4}$ is as follows:

$F e (s) + H_{2} S O_{4} (a q) \to F e S O_{4} (a q) + H_{2} (g)$

Question 7

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

Solution:

Zinc is more reactive than iron. So, when it is added to iron(II) sulphate solution, it displaces iron from the solution.

The chemical reaction is as follows:

$Z n (s) + F e S O_{4} (a q) \to Z n S O_{4} (a q) + F e (s)$

Question 8

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

(ii) Show the formation of $N a_{2} O$ and $M g O$ by the transfer of electrons.

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

Solution:

(iii) The ions present in

$N a_{2} O a r e N a^{+} a n d O^{2 -} .$

The ions present in $M g O a r e M g^{2 +} a n d O^{2 -} .$

Question 9

Why do ionic compounds have high melting points?

Solution:

The force of attraction in ionic bonds is very strong. Therefore, the ionic compounds require a lot of energy to overcome this bond. That is why ionic compounds have high melting points.

Question 10

Define the following terms.

(i) Mineral

(ii) Ore

(iii) Gangue

Solution:

(i) Mineral are the naturally occurring materials in which metals or their compounds are found on earth.

(ii) Ores are the minerals from which metals can be extracted profitably.

(iii) Gangues are the impurities present in an ore.

Question 11

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

Solution:

Silver and gold

Question 12

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

Solution:

A metal can be obtained from its oxide by the process of reduction.

Question 13

Metallic oxides of zinc, magnesium and copper were heated with the following metals.

Metal	Zinc	Magnesium	Copper
Zinc oxide
Magnesium oxide
Copper oxide

In which cases will you find displacement reactions taking place?

Solution:

Metal	Zinc	Magnesium	Copper
Zinc oxide	No reaction	Displacement	No reaction
Magnesium oxide	No reaction	No reaction	No reaction
Copper oxide	Displacement	Displacement	No reaction

Question 14

Which metals do not corrode easily?

Solution:

Metals which are least reactive, such as silver, gold, etc. do not corrode easily.

Question 15

What are alloys?

Solution:

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. The properties of an alloy are different from the constituent matters.

Questions

Q1	Write the equations for the reaction of zinc with each of the following: i) Sodium hydroxide solution ii) Copper sulphate solution

Q2	Why does silver not react with copper sulphate solution?

Q3	Why is it that sodium chloride (NaCl) does not conduct electricity in the solid state whereas it conducts electricity when in the aqueous solution as well as in the molten state?

Q4	What is a covalent bond?

Q5	State the property of the metal being utilized in the following: a) Zinc in galvanization b) Aluminium in thermite welding

Q6	What is an electron dot representation?

Q7	Differentiate between minerals and ores.

Q8	Give 2 examples of the following: i) Metals purified by distillation ii) Metals purified by liquation method iii) Elements removed by oxidation

Q9	Name the elements present in the following covalent compounds. a) Methane b) Ammonia c) Alcohol d) Urea

Q10	In what way is dilute nitric acid different from other acids when it reacts with metals? Write the equation for the reaction of dilute nitric acid with copper.

Q11	What are the main physical properties of metals?

Q12	What are the main physical properties of non-metals?

Q13	Distinguish between roasting and calcination.

Q14	Explain the reaction of metal with water.

Q15	Compare the properties of a typical metal and a non-metal on the basis of the following: a) Electronic configuration b) Physical state c) Colour d) Density

Q16	What are the factors for corrosion? State under what conditions corrosion is faster. Explain why corrosion can be an advantage in some cases.

Q17	Explain ionic bond with the example of sodium chloride.

Q18	Name the steps involved in extraction of a metal from its ore.

Q19	Explain the reactivity series of metals.

Q20	What is an alloy? What are the various uses of alloy?

Questions

Q1	Write the equations for the reaction of zinc with each of the following: i) Sodium hydroxide solution ii) Copper sulphate solution

A1	i) Zn (s) + 2NaOH (aq) → Na₂ZnO₂(aq) + H₂(g) ii) Zn (s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu (s)

Q2	Why does silver not react with copper sulphate solution?

A2	Silver does not react with copper sulphate solution because silver is less reactive than copper and thus, it is not able to displace copper from its salt solution. Ag + CuSO₄ → No reaction

Q3	Why is it that sodium chloride (NaCl) does not conduct electricity in the solid state whereas it conducts electricity when in the aqueous solution as well as in the molten state?

A3	It is the property of the ionic compounds by virtue of which they do not conduct electricity in the solid state but conduct electricity in the aqueous solution and in the molten state. Sodium chloride being an ionic compound shows the same property.

Q4	What is a covalent bond?

Q5	State the property of the metal being utilized in the following: a) Zinc in galvanization b) Aluminium in thermite welding

A5	(i) The property of zinc which is utilized in galvanization is the metal’s electropositive nature due to which it imparts protection to the substance on which it is coated. (ii) The property of aluminium which is utilized in thermite welding is the metal’s high affinity for oxygen.

Q6	What is an electron dot representation?

A6	The outermost electrons of an atom are known as valence electrons. Electron dot representation is the representation of valence electrons by putting dots(s) on the symbol of the element, one dot for each valence electron.

Q7	Differentiate between minerals and ores.

A7	The natural forms in which metals or their compounds are found on the earth are called minerals. Those minerals from which metals can be extracted conveniently and economically are called ores.

Q8	Give 2 examples of the following: i) Metals purified by distillation ii) Metals purified by liquation method iii) Elements removed by oxidation

A8	i) Zinc and mercury ii) Lead and tin iii) Carbon and sulphur

Q9	Name the elements present in the following covalent compounds. a) Methane b) Ammonia c) Alcohol d) Urea

A9	a) Elements present in methane are carbon and hydrogen. b) Elements present in ammonia are nitrogen and hydrogen. c) Elements present in alcohol are carbon, hydrogen and oxygen. d) Elements present in urea are carbon, oxygen, nitrogen and hydrogen.

Q10	In what way is dilute nitric acid different from other acids when it reacts with metals? Write the equation for the reaction of dilute nitric acid with copper.

A10

In the electrochemical series, metals lying above hydrogen give hydrogen from the acid. In case of nitric acid, which is a strong oxidising agent, hydrogen produced in the nascent state reduces excess nitric acid and produces water and a reduction product of nitric acid. The reduction product depends on the concentration of the acid.

4 Cu + 8 HNO₃ → 3 Cu (NO₃)₂ +2NO (nitric oxide) + 4 H₂O

Q11	What are the main physical properties of metals?

A11

The main physical properties of metals are:

a) Metals are malleable. They can be beaten into thin sheets without breaking.

b) Metals are ductile. They can be drawn into thin wires.

c) Metals are good conductor of heat. They allow heat to pass through them.

d)Metals allow electricity to pass through them.

e) Metals are shiny.

f) Metals are generally hard.

g) Metals are solid at room temperature and have high boiling and melting points.

Q12	What are the main physical properties of non-metals?

A12

The main physical properties of non- metals are:

a) Non-metals are brittle. They cannot be beaten into thin sheets without breaking.

b) Non-metals cannot be drawn into thin wires.

c) Non-metals do not conduct electricity.

d) They do not allow heat to pass through them.

e) Non-metals are dull.

f) Non-metals are generally soft.

Q13	Distinguish between roasting and calcination.

A13

Ores found in the form of sulphide and carbonates are first converted into their oxides by the process of roasting and calcination.

Roasting is the heating of sulphide ores in the presence of excess air to convert them into oxides whereas calcination is the heating of carbonate ores in the limited supply of air to convert them into oxides.

Q14	Explain the reaction of metal with water.

A14

Metals react with water and produce metal oxides and hydrogen gas:

Metal + Water → Metal oxide + Hydrogen

Metal oxides that are soluble in water dissolve in it to form metal hydroxides:

Metal oxide + Water → Metal hydroxide

All metals, however, do not react with water in the same manner. Metals such as potassium and sodium react violently with cold water. Calcium too reacts with cold water but the reaction is less violent.

Magnesium does not react with cold water. It reacts with hot water. Metals such as aluminium, iron and zinc do not react with cold or hot water. But they do react with steam.

Metals such as lead, copper, silver and gold do not react with water at all.

Q15	Compare the properties of a typical metal and a non-metal on the basis of the following: a) Electronic configuration b) Physical state c) Colour d) Density

A15

a) Electronic configuration: Atoms of metals have 1, 2 or 3 electrons in the outermost shells. Atoms of non- metals have 4, 5, 6, 7 electrons in outermost shells.

b) Physical state: Metals are solid at room temperature except mercury, which is liquid. Non- metals are found in solid, liquid or gaseous state at room temperature.

c) Colour: Metals usually have a grey or silver colour except copper and gold. Non-metals are found in different colours.

d) Density: Metals generally have high densities whereas non- metals have low densities.

Q16	What are the factors for corrosion? State under what conditions corrosion is faster. Explain why corrosion can be an advantage in some cases.

A16

When a metallic surface is attacked by the action of air, moisture or any other substance around it, the metal is said to corrode, and this phenomenon is known as corrosion. It is also called the weeping of metal.

Some of the factors that cause corrosion are:

• Presence of impurities

• Reactivity of metal

• Presence of air, moisture, gases like CO₂and SO₂

• Presence of electrolytes

Corrosion is faster when other than the presence of oxygen and moisture, it is noticed that:

a) Metals which are positioned higher in the activity series corrode more easily.

b) Dissolved salts in water act as electrolyte and add to the rate of corrosion.

c) The presence of a metal which is less reactive than iron increases the rate of rusting of iron because it favours the more reactive metals like iron, to lose electrons and get oxidised.

d) The presence of pollutants like NO₂ and CO₂ increases rusting.Sometimes corrosion of metals is an advantage, as it stops the metal underneath from further damage. To cite an example, on exposure to air, the surface of metals like aluminium and zinc forms layers of their oxides which are very sticky and impervious in nature, and therefore act as a shielding layer. This layer protects the metal from further damage. That explains why the things made up of aluminium do not corrode easily.

Q17	Explain ionic bond with the example of sodium chloride.

A17

An ionic bond is formed due to the transfer of electrons from a metal to a non-metal. In this course, due to transfer of electrons, metals get positive charge and non-metals, having accepted electrons, get negative charge. In other words, the bond formed between the positive ions and the negative ions is called ionic bond.

Formation of sodium chloride (NaCl):

In sodium chloride; sodium is an alkali metal and chlorine is a non-metal.

Atomic number of sodium = 11

Electronic configuration of sodium: 2, 8, 1

Number of electrons in its outermost orbit = 1

Valence electrons = Number of electrons in the outermost orbit = 1

Atomic number of chlorine = 17

Electronic configuration of chlorine: 2, 8, 7

Number of electrons in the outermost orbit = 7

Therefore, valence electrons = 7

Sodium has one valence electron and chlorine has seven. Sodium requires to lose one electron to obtain stable configuration and chlorine requires to gain one electron in order to obtain a stable electronic configuration. This way, in order to obtain a stable configuration, sodium transfers one electron to chlorine.

Having lost one electron, sodium gets one positive charge (⁺) and after the addition of one electron, chlorine gets one negative charge (^-). Thus ionic bond is formed between sodium and chlorine. Since sodium chloride is formed because of ionic bond; it is therefore called an ionic compound.

Q18	Name the steps involved in extraction of a metal from its ore.

A18

i) Crushing and grinding (to increase the surface area)

ii) Concentration (to reduce the bulk by removal of impurities)

a) Gravity separation (Heavy metals)

b) Froth floatation (Sulphur)

c) Electromagnetic separation (Iron)

d) Chemical separation or Leaching (Aluminium)

iii) Oxidation of ore (to make sure that the metal to be extracted gets converted toits oxide) by roasting or calcination (the process is selected depending upon the type of metal in the ore)

iv) Reduction of the oxides formed

a) Chemical reduction

b) Electrolytic reduction

v) Metal is extracted (but is impure and hence undergoes refining) by:

a) Liquation (done on the basis of melting points)

b) Distillation (used to refine volatile metals)

c) Oxidation (used to refine metals containing oxidisable impurities)

d) Poling (employed mainly for copper)

e) Electro-refining (employed for reactive metals)

Q19	Explain the reactivity series of metals.

A19	The reactivity series of metals is an arrangement of metals in vertical column in the decreasing order of its activity. The reactivity series of some of the common metals is given below. Hydrogen, though not a metal, yet has been placed in the reactivity series of metals.

Q20	What is an alloy? What are the various uses of alloy?

A20

An alloy is the metallic material formed by the homogeneous mixture of two or more metals or of one or more metals with certain non-metallic elements, by different physical processes like fusion, electrolytic deposition, etc.

Generally metals like copper, zinc, tin, chromium, nickel and silver are used to make alloys with other metals and non-metals like carbon, boron, sulphur, zinc, etc. The combination of metals in alloy determines the chemical and physical properties of the alloy.

There are many possible combinations of different metals to form alloys. Each alloy has its own specific properties and uses. The uses of alloys depend upon their metallic composition and complexity of the alloy. Some common uses of alloys are as follows:

Uses of aluminum alloys: Compared to the metal aluminium, alloys of aluminium are better conductors and are stronger. These properties have made its wide scale use in the manufacturing of electrical equipments, automobile engine parts, and also in furniture-making. Due to high strength, they are also used in high altitude flying to endure high pressure and stress.

Uses of copper alloys: Similar to the metal copper, alloys of copper too are good conductors of heat and electricity, and are highly ductile as well as corrosion-resistant. They are mainly used in automobiles as heat exchanger, sleeve bearing and also in the manufacture of electrical equipment.

Uses of iron alloys: The most common alloy of iron, which is used for many commercial purposes, is stainless steel. Iron alloys are mainly used in electronics, rail industries and agriculture.

Uses of nickel alloys: Alloys of nickel have high heat resistance ability and good corrosion resistance. That is the reason why they are used for the manufacture of aircraft gas turbines, petrochemical industries and nuclear power systems.

$\begin{array}{l} 2 M S + 3 O_{2} \overset{R o a s t i n g}{\to} 2 M O + 2 S O_{2} \\ M O + C \to M + C O \end{array}$

Lesson:Metals and Non-metals F

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