lakhmir singh chemistry class 10 solutions metals and non metals

Lakhmir Singh Chemistry Class 10 Solutions Metals And Non-metals

Lakhmir Singh Chemistry Class 10 Solutions Page No:131

Question 1:
Name one metal and one non-metal which exist in liquid state at room temperature.
Solution :
Metal – Mercury.
Non metal – Bromine.

Question 2:
Why are metals called electropositive elements whereas non-metals are called electronegative elements ?
Solution :
Metals are electropositive elements because they can form positive ions by losing electrons.
Non-metals are electronegative elements because they can form negative ions by gaining electrons.

Question 3:
(a) Name the most abundant metal in the earth’s crust.
(b) Name the most abundant non-metal in the earth’s crust.
Solution :
(a) Aluminium.
(b) Oxygen.

Lakhmir Singh Chemistry Class 10 Solutions Page No:132

Question 4:
Name one metal which has a low melting point.
Solution :
Cesium.

Question 5:
Name the metal which is the poorest conductor of heat.
Solution :
Lead.

Question 6:
State whether the following statement is true or false :
Non-metals react with dilute acids to produce a gas which burns with a ‘pop’ sound.
Solution :
False.

Question 7:
From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal :
(i) which reacts with water only on boiling, and
(ii) another which does not react even with steam.
Solution :
(i) Aluminium.
(ii) Copper.

Question 8:
What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes ?
Solution :
Iron nail gets covered with a red-brown coating of copper metal; The blue colour of copper sulphate solution fades gradually.

Question 9:
What is aqua-regia ? Name two special metals which are insoluble in common reagents but dissolve in aqua-regia.
Solution :
Aqua-regia is a freshly prepared mixture of one part of concentrated nitric acid and 3 parts of concentrated hydrochloric acid. Gold and platinum dissolve in aqua-regia

Question 10:
Give the names and formulae of (a) two acidic oxides, and (b) two basic oxides.
Solution :
(a) Carbon dioxide and sulphur dioxide.
(b) Sodium oxide and magnesium oxide.

Question 11:
What name is given to those metal oxides which show basic as well as acidic behaviour ?
Solution :
Amphoteric oxides.

Question 12:
Name two metals which form amphoteric oxides.
Solution :
Aluminium and zinc.

Question 13:
A copper coin is kept immersed in a solution of silver nitrate for some time. What will happen to the coin and the colour of the solution ?
Solution :
Copper coin will get a shining greyish white coating of silver metal. The color of the solution will turn blue.

Question 14:
Which property of copper and aluminium makes them suitable :
(a) for making cooking utensils and boilers ?
(b) for making electric wires ?
Solution :
(a) High thermal conductivity.
(b) High electrical conductivity.

Question 15:
Write the names and formulae of (a) a metal hydride, and (b) a non-metal hydride.
Solution :
Sodium hydride,Hydrogen sulphide

Question 16:
Name the metal which has been placed :
(a) at the bottom of the reactivity series
(b) at the top of the reactivity series
(c) just below copper in the reactivity series
Solution :
(a) Gold.
(b) Potassium.
(c) Mercury.

Question 17:
Which of the two metals is more reactive : copper or silver ?
Solution :
Copper.

Question 18:
(a) Name one metal which is stored in kerosene oil.
(b) Name one non-metal which is stored under water.
Solution :
(a) Sodium.
(b) White phosphorus.

Question 19:
Write equation for the reaction of :
(a) sodium with oxygen
(b) magnesium with oxygen
Solution :

Question 20:
Name two metals which are used :
(a) for making electric wires.
(b) for making domestic utensils and factory equipment.
(c) for making jewellery and to decorate sweets.
Solution :
(a) Aluminium and copper.
(b) Copper and aluminium.
(c) Gold and silver.

Question 21:
Which metal foil is used for packing some of the medicine tablets ?
Solution :
Aluminium foil.

Question 22:
Name the non-metal which is used :
(a) to convert vegetable oil into vegetable ghee(solid fat).
(b) as a rocket fuel (in liquid form).
(c) to make electrodes of dry cells.
(d) to preserve food materials.
(e) in the vulcanisation of rubber.
Solution :
(a) Hydrogen.
(b) Hydrogen.
(c) Carbon.
(d) Nitrogen.
(e) Sulphur.

Question 23:
Name one property which is characteristic of (a) metals, and (b) non-metals.
Solution :
(a) Metals are malleable.
(b) Non-metals are non-malleable.

Question 24:
What is meant by “brittleness” ? Which type of elements usually show brittleness : metals or non-metals ?
Solution :
Brittleness is the property of being brittle i.e. breaking easily.
Non-metals show brittleness.

Question 25:
What will happen if a strip of zinc is immersed in a solution of copper sulphate ?
Solution :
When a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper sulphate solution fades gradually and red brown coating of copper is deposited on zinc strip.

Question 26:
What will happen if a strip of copper is kept immersed in a solution of silver nitrate (AgN0₃) ?
Solution :
When a strip of copper metal is immersed in silver nitrate solution, the solution gradually becomes blue and a shining greyish-white deposit of silver metal is formed on copper strip.

Question 27:
What happens when iron nails are put into copper sulphate solution ?
Solution :
When iron nails are placed in copper sulphate solution, the blue colour of copper sulphate solution fades gradually and red-brown copper metal is formed.

Question 28:
How would you show that silver is chemically less reactive than copper ?
Solution :
If a strip of silver metal is kept immersed in copper sulphate solution for some time, then no reaction occurs. This shows that silver is not able to displace copper from copper sulphate solution.

Question 29:
Give reasons for the following :
Blue colour of copper sulphate solution is destroyed when iron filings are added to it.
Solution :
Blue color of copper sulphate is destroyed because iron displaces copper from copper sulphate solution as iron is more reactive than copper.

Lakhmir Singh Chemistry Class 10 Solutions Page No:133

Question 30:
Name a non-metal having a very high melting point.
Solution :
Diamond.

Question 31:
Which property of graphite is utilised in making electrodes ?
Solution :
Since graphite is a good conductor of electricity, it is used in making electrodes.

Question 32:
Name two non-metals which are both brittle and non-ductile.
Solution :
Sulphur and phosphorus.

Question 33:
Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.
Solution :
The surface of some metals acquires a dull appearance when exposed to air for a long time because metals form a thin layer of oxides, carbonates or sulphide on their surface by the slow action of various gases present in air.

Question 34:
Complete and balance the following equations :

Solution :

Question 35:
Fill in the following blanks with suitable words :
(a) Magnesium liberates………………… gas on reacting with hot boiling water.
(b) The white powder formed when magnesium ribbon burns in oxygen is of………………………………..
(c) Ordinary aluminium strips are not attacked by water because of the presence of a layer of………………………………… on the surface of aluminium.
(d) A metal having low melting point is……………………. but a non-metal having very high melting point is………………………
(e) Calcium is a…………….. reactive metal than sodium.
Solution :
(a)Hydrogen.
(b) Magnesium oxide.
(c) Aluminium oxide.
(d) Sodium; Diamond.
(e) Less.

Question 36:
(a) What is meant by saying that the metals are malleable and ductile ? Explain with examples.
(b) Name two metals which are both malleable and ductile.
(c) Which property of iron metal is utilised in producing iron sheets required for making buckets ?
(d) Which property of copper metal is utilised in making thin wires ?
Solution :
(a) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
Example: Aluminium.
Metals are ductile i.e. they can be drawn into thin wires.
Example: Copper.
(b) Aluminium and copper.
(c) Malleability.
(d) Ductility.

Question 37:
Name two metals which react violently with cold water. Write any three observations you would make when such a metal is dropped into water. How would you identify the gas evolved, if any, during the reaction ?
Solution :
Sodium and potassium metals react violently with cold water.
Observations:
1. Metal starts moving over the surface of water making a hissing sound.
2. Metal starts reacting with water causing little explosions.
3. Soon the metal catches fire and starts burning.

Question 38:
(a) With the help of examples, describe how metal oxides differ from non-metal oxides.
(b) Which of the following elements would yield : (i) an acidic oxide, (ii) a basic oxide, and (iii) a neutral oxide ?
Na, S, C, K, H
Solution :
(a)M etal oxides are basic in nature and turn red litmus blue. For example: Magnesium oxide.
Non-metal oxides are acidic or neutral in nature. The acidic oxides turn blue litmus red. For example: Carbon dioxide.
(b) (i) Acidic oxide: S, C
(ii) Basic oxide: Na, K
(iii) Neutral oxide: H

Question 39:
(a) What are amphoteric oxides ? Give two examples of amphoteric oxides.
(b) Choose the acidic oxides, basic oxides and neutral oxides from the following :
Na₂O ; CO₂ ; CO ; SO₂; MgO ; N₂O ; H₂O.
(c) Which of the following are amphoteric oxides :
MgO, ZnO, P₂O₃, Al₂O₃, NO₂
Solution :
(a) Those metal oxides which show basic as well as acidic behavior are known as amphoteric oxides.
Example: Aluminium oxide and zinc oxide.
(b) Acidic oxide – CO 2 , CO, SO 2 and N 2 O; Basic oxide – Na 2 O, MgO; Neutral oxide – H 2 O.
(c) ZnO, Al 2 O 3 .

Question 40:
(a) What is the nature of the oxide SO₂ ? What happens when it is dissolved in water ? Write the chemical equation of the reaction involved.
(b) What is the nature of the oxide Na₂O ? What happens when it is dissolved in water ? Write the chemical equation of the reaction inolved.
Solution :
(a) SO2 is acidic in nature. When dissolved in water, it produces sulphurous acid.

(b) Na2O is basic in nature. When dissolved in water, it forms an alkali called sodium hydroxide.

Question 41:
(a) What type of oxides are formed when non-metals react with oxygen ? Explain with an example.
(b) What type of oxides are formed when metals combine with oxygen ? Explain with the help of an example.
Solution :
(a) When non-metals react with oxygen, they form acidic oxides or neutral oxides.
Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide. Hydrogen reacts with oxygen
(b)When metals combine with oxygen, they form basic oxides.
Example: Sodium reacts with oxygen to form a basic oxide called sodium oxide.

Question 42:
(a) Explain why, metals usually do not liberate hydrogen gas with dilute nitric acid.
(b) Name two metals which can, however, liberate hydrogen gas from very dilute nitric acid.
Solution :
Metals do not liberate hydrogen gas with nitric acid because nitric acid is a strong oxidizing agent. So, as soon as hydrogen gas is formed in the reaction between a metal and dilute nitric acid, the nitric acid oxidises
this hydrogen to water.
(b) Magnesium and manganese.

Question 43:
(a) How do metals react with hydrogen ? Explain with an example.
(b) How do non-metals react with hydrogen ? Explain with an example.
Solution :
(a) Most of the metals do not react with hydrogen. Only a few reactive metals react with hydrogen to form metal hydrides. For example: When hydrogen gas is passed over heated sodium, then sodium hydride is formed.
(b) Non-metals react with hydrogen to form covalent hydrides. For example: Sulphur combines with hydrogen to form hydrogen sulphide.

Question 44:
(a) What happens when calcium reacts with chlorine ? Write an equation for the reaction which takes place.
(b) What happens when magnesium reacts with very dilute nitric acid ? Write an equation for the reaction involved.
Solution :
(a)Calcium reacts vigorously with chlorine to form an ionic chloride called calcium chloride.

(b)Magnesium reacts with very dilute nitric acid to form magnesium nitrate and hydrogen gas.

Question 45:
(a) Arrange the following metals in order of their chemical reactivity, placing the most reactive metal first :
Magnesium, Copper, Iron, Sodium, Zinc, Lead, Calcium.
(b) What happens when a rod of zinc metal is dipped into a solution of copper sulphate ? Give chemical equation of the reaction involved.
Solution :
(a) Sodium > Calcium > Magnesium > Zinc > Iron > Lead > Copper
(b) When a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper sulphate solution fades gradually and red brown coating of copper is deposited on the zinc strip.

Lakhmir Singh Chemistry Class 10 Solutions Page No:134

Question 46:
A copper plate was dipped in AgNO₃ After certain time, silver from the solution was deposited on the copper plate. State the reason why it happened. Give the chemical equation of the reaction involved.
Solution :
Silver gets deposited on the copper plate because copper is more reactive than silver and hence displaces silver from silver nitrate solution.

Question 47:
State five uses of metals and five of non-metals.
Solution :
Uses of metals:
(i) Lead metal is used in making car batteries.
(ii) Zinc is used for galvanizing iron to protect it from rusting.
(iii) Iron, copper and aluminium are used to make utensils.
(iv) Copper and aluminium metals are used to make electrical wires.
(v) Aluminium is used to make aluminium foil for packaging materials.
Uses of non-metals:
(i) Hydrogen is used in the hydrogenation of vegetable oils.
(ii) Carbon is used to make electrodes of electrolytic cells and dry cells.
(iii) Nitrogen is used in the manufacture of ammonia, nitric acid and fertilizers.
(iv) Sulphur is used for producing sulphuric acid.
(v) Liquid hydrogen is used as rocket fuel.

Question 48:
State one use each of the following metals :
Copper, Aluminium, Iron, Silver, Gold, Mercury
Solution :
(i) Copper – Copper is used to make wires to carry electric current.
(ii) Aluminium – Aluminium foils are used in packaging of food materials.
(iii) Iron – Iron is used to make utensils.
(iv) Silver – Silver is used to make jewellery.
(v) Gold – Gold is used to make jewellery.
(vi) Mercury – Mercury is used in thermometers.

Question 49:
(a) State one use each of the following non-metals :
Hydrogen, Carbon (as Graphite), Nitrogen, Sulphur
(b) Name the metal which is used in making thermometers.
Solution :
(a) (i) Hydrogen – Hydrogen is used in the hydrogenation of vegetable oils.
(ii) Carbon is used to make electrodes of electrolytic cells and dry cells.
(iii) Nitrogen is used in the manufacture of ammonia, nitric acid and fertilizers.
(iv) Sulphur is used in making sulphuric acid.
(b) Mercury

Question 50:
(a) Why does aluminium not react with water under ordinary conditions ?
(b) Name two metals which can displace hydrogen from dilute acids.
(c) Name two metals which cannot displace hydrogen from dilute acids.
Solution :
(a) Aluminium metal does not react with water under ordinary conditions because of the presence of a thin layer of aluminium oxide on its surface.
(b) Sodium and magnesium.
(c) Copper and silver.

Question 51:
(a) Why is sodium kept immersed in kerosene oil ?
(b) Why is white phosphorus kept immersed under water ?
(c) Can we keep sodium immersed under water ? Why ?
Solution :
(a) Sodium is a very reactive metal so it reacts vigorously with the oxygen of air and catches fire. It is kept immersed in kerosene oil to protect it from the action of oxygen, moisture and carbon dioxide of air and to prevent accidental fires.
(b) White phosphorus is kept immersed in water because it reacts spontaneously with oxygen of air to form phosphorus pentoxide but does not react with water.
(c) No, because sodium reacts vigorously with water to form sodium hydroxide and hydrogen.

Question 52:
(a) Describe the reaction of potassium with water. Write the equation of the reaction involved.
(b) Write an equation of the reaction of iron with steam. Indicate the physical states of all the reactants and products.
(c) Which gas is produced when dilute hydrochloric acid is added to a reactive metal ?
Solution :
(a) Potassium reacts violently with cold water to form potassium hydroxide and hydrogen gas.

(c) Hydrogen.

Question 53:
(a) Give one example, with equation, of the displacement of hydrogen by a metal from an acid.
(b) Name two metals (other than zinc and iron) which can displace hydrogen from dilute hydrochloric acid ?
Solution :
(a) Magnesium reacts with very dilute nitric acid to form magnesium nitrate and hydrogen gas.

(b) Magnesium and aluminium.

Question 54:
What is the action of water on (a) sodium (b) magnesium, and (c) aluminium ? Write equations of the chemical reactions involved.
Solution :
(a) Sodium reacts vigorously with cold water forming sodium hydroxide and hydrogen gas.

Question 55:
You are given samples of three metals — sodium, magnesium and copper. Suggest any two activities to arrange them in order of their decreasing reactivities.
Solution :
(i) When sodium, magnesium and copper are left in air, sodium reacts vigorously with oxygen to form sodium oxide, magnesium reacts with oxygen to form magnesium oxide only on heating , whereas copper does not burn in air even on strong heating. It reacts only on prolonged heating. This shows that sodium is most reactive, then magnesium and copper is the least reactive among the three.
(ii) Sodium reacts vigorously with cold water to form sodium hydroxide and hydrogen, magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen but copper does not react even with steam. This shows that sodium is highly reactive; magnesium is less reactive than sodium and copper is the least reactive among the three.

Question 56:
(a) Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.
(b) What special name is given to substances like aluminium oxide.
(c) Name another metal oxide which behaves like aluminium oxide.
Solution :

Question 57:
(a) What happens when calcium reacts with water ? Write the chemical equation of the reaction of calcium with water.
(b) Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick ?
Solution :

When hydrogen gas is ignited with a burning matchstick, it produces a ‘pop’sound.

Question 58:
You are given a dry cell, a torch bulb with holder, wires and crocodile clips. How would you use them to distinguish between samples of metals and non-metals ?
Solution :
We would create an apparatus using dry cell, a torch bulb fitted in a holder and some connecting wires with crocodile clips and connect them to make an electric circuit. Then insert a piece of sulphur between the crocodile clips and the bulb does not light up at all. This means that sulphur does not allow the electric current to pass through it. Now insert a piece of copper between the crocodile clips and the bulb will light up. This observation shows that non metals (ex- sulphur) do not conduct electricity and metals (ex- copper) conduct electricity.

Question 59:
State any five physical properties of metals and five physical properties of non-metals.
Solution :
Properties of metals:
(i) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
(ii) Metals are ductile i.e. they can be drawn into thin wires.
(iii) Metals are good conductors of heat and electricity.
(iv) Metals are lustrous.
(v) Metals are generally hard.
Properties of non-metals:
(i) Non-metals are non-malleable i.e. they cannot be beaten into thin sheets with a hammer.
(ii) Non-metals are non-ductile i.e. they cannot be drawn into thin wires.
(iii) Non-m etals are bad conductors of heat and electricity.
(iv) Non-m etals are non- lustrous.
(v) Non-m etals are generally soft .

Question 60:
(a) Name two physical properties each of sodium and carbon in which their behaviour is not as expected from their classification as metal and non-metal respectively.
(b) Name two metals whose melting points are so low that they melt when held in the hand.
Solution :
(a) Sodium metal: Soft, low melting point
Carbon non-metal: graphite conducts electricity; diamond has a very high melting point.
(b) Gallium and cesium.

Question 61:
Metals are said to be shiny. Why do metals generally appear to be dull ? How can their brightness be restored ?
Solution :
Metals lose their shine or brightness on keeping in air for a long time and acquire a dull appearence due to the formation of a thin layer of oxide, carbonate or sulphide on their surface by the slow action of various gases present in air.
Brightness of metals can be restored by rubbing the dull surface of the metal object with a sand paper, then the outer corroded layer is removed and the metal object becomes shiny and bright once again.

Question 62:
(a) What are metals ? Name five metals.
(b) Name a metal which is so soft that it can be cut with a knife.
(c) Name the metal which is the best conductor of heat and electricity.
(d) What happens when a metal reacts with dilute hydrochloric acid ? Explain with the help of an example.
(e) Write the equations for the reactions of :
(i) Magnesium with dilute hydrochloric acid
(ii) Aluminium with dilute hydrochloric acid
(iii) Zinc with dilute hydrochloric acid
(iv) Iron with dilute hydrochloric acid
Name the products formed in each case. Also indicate the physical states of all the substances involved.
Solution :
(a) Metals are the elements that conduct heat and electricity, and are malleable and ductile.
Example: Iron, aluminium, copper, gold and silver.
(b) Sodium
(c) Silver
(d) When a metal reacts with dilute hydrochloric acid, it forms metal chloride and hydrogen gas.
Example: Magnesium reacts rapidly with dilute hydrochloric acid to form magnesium chloride and hydrogen.

Lakhmir Singh Chemistry Class 10 Solutions Page No:135

Question 63:
(a) Define non-metals. Give five examples of non-metals.
(b) Name a non-metal which conducts electricity.
(c) Name a non-metal having lustre (shining surface).
(d) Name a non-metal which is extremely hard.
(e) How do non-metals react with oxygen ? Explain with an example. Give equation of the reaction involved. What is the nature of the product formed ? How will you demonstrate it ?
Solution :
(a)Non-metals are the elements that do not conduct heat and electricity and are neither malleable nor ductile.
Example: Carbon, sulphur, phosphorus, silicon and oxygen.
(b) Carbon.
(c) Iodine.
(d) Carbon (Diamond).
(e) Non-metals react with oxygen to form acidic oxides or neutral oxides. Carbon burns in air to form carbon dioxide.

The nature of the product formed is acidic. When carbon dioxide dissolves in water, it forms carbonic acid. It turns blue litmus to red which shows it is acidic in nature.

Question 64:
(a) What is meant by the reactivity series of metals ? Arrange the following metals in an increasing order of their reactivities towards water :
Zinc, Iron, Magnesium, Sodium
(b) Hydrogen is not a metal but still it has been assigned a place in the reactivity series of metals. Why ?
(c) Name one metal more reactive and another less reactive than hydrogen.
(d) Name one metal which displaces copper from copper sulphate solution and one which does not.
(e) Name one metal which displaces silver from silver nitrate solution and one which does not.
Solution :
(a) The arrangement of metals in a vertical column in the order of decreasing reactivities is called reactivity series.
Increasing order of reactivity: Iron < zinc < magnesium < sodium
(b) Though hydrogen is not a metal but it has been placed in the reactivity series of metals due to the fact that like metals, hydrogen also loses electrons and forms positive ions.
(c) Lead is more reactive than hydrogen and copper is less reactive than hydrogen.
(d) Zinc displaces copper from copper sulphate solution and mercury does not displace copper from copper sulphate solution.
(e) Copper displaces silver from silver nitrate solution and gold does not.

Question 65:
(a) State any three differences between the physical properties of metals and non-metals.
(b) Differentiate between metals and non-metals on the basis of their chemical properties.
(c) State three reasons (of which at least one must be chemical) for believing that sodium is a metal.
(d) State three reasons (of which at least one must be chemical) for believing that sulphur is a non-metal.
(e) Which non-metal has been placed in the reactivity series of metals ?
Solution :
(a) Difference between metals and non-metals:
Metals
(i) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
(ii) Metals are ductile i.e. they can be drawn into thin wires.
(iii) Metals are good conductors of heat and electricity.
Non-metals
(i) Non-metals are non-malleable i.e. they cannot be beaten into thin sheets with a hammer.
(ii) Non-metals are non-ductile i.e. they cannot be drawn into thin wires.
(iii) Non-metals are bad conductors of heat and electricity.
(b) Difference between metals and non-metals:
Metals
(i) Metals form basic oxides.
(ii) Metals displace hydrogen from water
(iii) Metals displace hydrogen from dilute acids.
Non-metals
(i) Non-metals form acidic or neutral oxides.
(ii) Non-metals do not react with water.
(iii) Non-metals do not react with dilute acids.
(c) Sodium is a solid, it conducts electricity and forms basic oxides.
(d) Sulphur is a non-metal as it is brittle, non-ductile, non-conductor of electricity and forms acidic oxides.
(e) Hydrogen.

Lakhmir Singh Chemistry Class 10 Solutions Page No:136

Question 89:
An element E forms an oxide E₂ An aqueous solution of E₂O turns red litmus paper blue.
(a) What is the nature of the oxide E₂O ?
(b) State whether element E is a metal or a non-metal.
(a) Give one example of an element like E.
Solution :
(a) Basic oxide.
(b) Metal .
(c) Sodium, Na .

Question 90:
Metal A burns in air, on heating, to form an oxide A₂O₃ whereas another metal B burns in air only on strong heating to form an oxide BO. The two oxides A₂O₃ and BO can react with hydrochloric acid as well as sodium hydroxide solution to form the corresponding salts and water.
(a) What is the nature of oxide A₂O₃ ?
(b) What is the nature of oxide BO ?
(c) Name one metal like A.
(d) Name one metal like B.
Solution :
(a) Amphoteric oxide .
(b) Amphoteric oxide .
(c) Aluminium, Al.
(d) Zinc, Zn .

Question 91:
An element X forms two oxides XO and XO₂. The oxide XO has no action on litmus solution but oxide X0₂ turns litmus solution red.
(a) What is the nature of oxide XO ?
(b) What is the nature of oxide XO₂ ?
(c) Would you call element X a metal or a non-metal ? Give reason for your choice.
(d) Can you give an example of element like X ?
Solution :
(a) Neutral oxide.
(b) Acidic o xide .
(c) X is non-metal because non-metals form acidic and basic oxide .
(d) Carbon, C .

Question 92:
State and explain the reactions, if any, of the following metals with a solution of copper sulphate :
(a) Gold (b) Copper (c) Zinc (d) Mercury
Solution :
(a) No displacement reaction will take place because go ld is less reactive than copper.
(b) No reaction will take place between copper and copper sulphate solution ; there is no reaction possible.
(c) Zinc displaces copper from copper sulphate solution to form zinc sulphate solution and copper metal because zinc is m ore reactive than copper .
(d) No displacement reaction will take place because mercury is less reactive than copper

Question 93:
(a) Give the names and formulae of one metal chloride and one non-metal chloride.
(b) State an important property in which these metal chloride and non-metal chloride differ.
(c) Why do they differ in this property ?
Solution :
Non-metal chloride:
Carbon tetrachloride, CCl 4
(b) Sodium chloride solution conducts electricity whereas carbon tetrachlori de does not conduct electricity.
(c) Sodium chloride is an ionic compoun d whereas carbon tetrachloride is a covalent compound.

Lakhmir Singh Chemistry Class 10 Solutions Page No:137

Question 94:
In a solution of lead acetate, a strip of metal M was dipped. After some time, lead from the solution was deposited on the metal strip. Which metal is more reactive, M or lead ?
Solution :
M is more reactive than lead since it is able to displace lead from lead acetate solution

Question 95:

On the basis of the above reactions, indicate which is most reactive and which is least reactive metal out of zinc, copper and iron.
Solution :
Zinc is most r eactive and copper is least reactive out of the three since iron displaced copper from its solution and zinc displaced iron from its solution.

Question 96:
Which of the following reactions will not occur ? Why not ?

Solution :
Reaction (a) will not occur because Cu is less reactive than Mg
Reaction (c) will also not occur because Fe is less reactive than Mg .

Question 97:
In nature, metal A is found in a free state while metal B is found in the form of its compounds. Which of these two will be nearer to the top of the activity series of metals ?
Solution :
Metal B will be nearer to the top of the activity series since it is highly reactive and is hence found in the form of its compounds and not in free state.

Question 98:
If A, B, C, D, E, F, G, H, I, J and K represent metals in the decreasing order of their reactivity, which one of them is most likely to occur in a free state in nature ?
Solution :
K being the lowest in the reactivity series is least reactive and is most likely to occur in a free state in nature.

Question 99:
(a) Name a metal for each case :
(i) It does not react with cold as well as hot water but reacts with steam.
(ii) It does not react with any physical state of water.
(b) When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so ?
Solution :
(a) (i) Iron (ii) Gold
(b) More heat is evolved during the reaction of sodium metal with water due to which the hyd rogen gas formed catches fire. O n the other hand, less heat is evolved during the reaction of calcium metal with water which cannot make the hydrogen gas bu rn .

Question 100:
A zinc plate was kept in a glass container having CuS0₄ On examining it was found that the blue colour of the solution is getting lighter and lighter. After a few days, when the zinc plate was taken out of the solution, a number of small holes were noticed in it. State the reason and give chemical equation of the reaction involved.
Solution :
Zinc metal is more reactive than copper. Some of the zinc metal of zinc plate dissolves and displaces copper from copper sulphate solution. This dissolving of zinc metal forms tiny holes in zinc plate. Blue colour of copper sulphate solution gets lighter and lighter due to the formation of colourless zinc sulphate solution.

Lakhmir Singh Chemistry Class 10 Solutions Page No:167

Question 1:
What is the name of the chemical bond formed :
(a) by the sharing of electrons between two atoms ?
(b) by the transfer of electrons from one atom to another ?
Solution :
(a) Covalent bond.
(b) Ionic bond .

Question 2:
Name a carbon containing molecule which has two double bonds.
Solution :
Carbon dioxide

Question 3:
What would be the electron-dot structure of carbon dioxide which has the formula C0₂ ?
Solution :

Question 4:
What type of chemical bond is formed between :
(a) potassium and bromine ?
(b) carbon and bromine ?
Solution :
(a) Ionic bond.
(b) Covalent bo nd.

Question 5:
(a) What do we call those particles which have more or less electrons than the normal atoms ?
(b) What do we call those particles which have more electrons than the normal atoms ?
(c) What do we call those particles which have less electrons than the normal atoms ?
Solution :
(a) Ions
(b) Anions
(c) Cations

Question 6:
(a) The atomic number of sodium is 11. What is the number of electrons in Na⁺ ?
(b) The atomic number of chlorine is 17. What is the number of electrons in Cl^– ?
Solution :
(a) No. of electrons in Na⁺ = 10
(b) No. of electrons in Cl^– = 18

Question 7:
The atomic number of an element X is 8 and that of element Y is 12. Write down the symbols of the ions you would expect to be formed from their atoms.
Solution :
X will form X 2-
Y will form Y 2+

Question 8:
(a) Write down the electronic configuration of (i) magnesium atom, and (ii)magnesium ion. (At. No. of Mg = 12)
(b) Write down the electronic configuration of (i) sulphur atom, and (ii) sulphide ion. (At. No. of S = 16)
Solution :
(a) (i) E.C of Mg = 2, 8, 2 (ii) E.C of Mg²⁺ = 2, 8
(b) (i) E.C of S = 2, 8, 6 (ii) E.C of S^2- = 2, 8, 8

Question 9:
What type of chemical bonds are present in a solid compound which has a high melting point, does not conduct electricity in the solid state but becomes a good conductor in the molten state ?
Solution :
Ionic bonds .

Question 10:
State whether the following statement is true or false :
The aqueous solution of an ionic compound conducts electricity because there are plenty of free electrons in the solution.
Solution :
False (It should be ‘ions’ in place of ‘electrons’) .

Question 11:
What type of bonds are present in hydrogen chloride and oxygen ?
Solution :
Covalent bond

Question 12:
Write the electron-dot structures for the following molecules :
(i) NaCl (ii) Cl₂
Solution :

Question 13:
What type of bonds are present in water molecule ? Draw the electron-dot structure of water (H₂0).
Solution :
Covalent bonds are present in a water molecule. Electron dot structure of water:

Question 14:
What type of bonds are present in methane (CH₄) and sodium chloride (NaCl) ?
Solution :
Methane: Covalent bonds
Sodium chloride: Ionic bonds

Question 15:
State one major difference between covalent and ionic bonds and give one example each of covalent and ionic compounds.
Solution :
Ionic compounds conduct electricity when dissolved in water or melted whereas covalent compounds do not conduct electricity.
Ionic compound – NaCl
Covalent compound – Carbon Dioxide

Question 16:
What type of bonds are present in the following molecules ? Draw their electron-dot structures.
(i) H₂ (ii) CH₄ (iii) Cl₂ (iv) O₂
Solution :
Covalent bonds are present in the given molecules
.

Question 17:
Which inert gas electron configuration do the Cl atoms in Cl₂ molecule resemble ? What is this electron configuration ?
Solution :
Argon; E.C = 2, 8,8

Question 18:
Which of the following compounds are ionic and which are covalent ?
Urea, Cane sugar, Hydrogen chloride, Sodium chloride, Ammonium chloride, Carbon tetrachloride, Ammonia, Alcohol, Magnesium chloride.
Solution :
Ionic compounds: Sodium chloride, Ammoniu m chloride, Magnesium chloride.
Covalent compounds:
Urea, Cane sugar, Hy drogen chloride,
Carbon tetrachloride, Ammonia, Alcohol .

Question 19:
Give one example each of the following :
(i) Amolecule containing a single covalent bond
(ii) Amolecule containing a double covalent bond
(iii) Amolecule containing a triple covalent bond
(iv) Acompound containing an ionic bond
Solution :
(i) Hydrog en
(ii) Oxygen
(iii) Nitrogen
(iv) Sodium chloride

Lakhmir Singh Chemistry Class 10 Solutions Page No:168

Question 20:
Fill in the blanks in the following sentences :
(i) Two atoms of the same element combine to form a molecule. The bond between them is known as…………………………………bond.
(ii) Two chlorine atoms combine to form a molecule. The bond between them is known as
(iii) In forming oxygen molecule,………….. electrons are shared by each atom of oxygen.
(iv) In forming N₂ molecule,……….. electrons are shared by each atom of nitrogen.
(v) The number of single covalent bonds in C₂H₂ molecule are…………………………
(vi) Melting points and boiling points of ionic compounds are generally………………… than those of covalent compounds.
Solution :
(i) Covalent
(ii) Covalent
(iii) Two
(iv) Three
(v) Two
(vi) Higher

Question 21:
(a) What is a covalent bond ? What type of bond exists in (i) CCl₄, and (ii) CaCl₂ ?
(b) What is an ionic bond ? What type of bond is present in oxygen molecule ?
Solution :
(a) The chemical bond formed by the sharing of electrons between two atoms is known as a covalent bond.
(i) Covalent bonds (ii) Ionic bonds
(b) The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond.
Covalent bond is present in an oxygen molecule.

Question 22:
(a) What is an ion ? Explain with examples.
(b) What is the nature of charge on (i) a cation, and (ii) an anion ?
(c) Name the cation and anion present in MgCl₂. Also write their symbols.
Solution :
(a) An ion is an electrically charged atom (or group of atoms). Example: Sodium ion, Na + , magnesium ion, Mg 2+ .
(b) (i) Positive charge (ii) Negative charge
(c) Cation: Magnesium ion, Mg 2+
Anion: Chloride ions, 2Cl –

Question 23:
(a) What type of chemical bond is present in chlorine molecule ? Explain your answer.
(b) Explain the formation of a chlorine molecule on the basis of electronic theory of valency.
Solution :
(a) Covalent bond ; Because whenever two atoms of the same element combine to form a molecule, a covalent bond is formed.
(b) The atomic number of chlorine is 17, so its electronic configuration is 2,8,7. Chlorine atom has 7 electrons in its outermost shell and needs 1 more electron to complete its octet and become stable.
It gets this electron by sharing with another chlorine atom. So, two chlorine atoms share one electron each to form a chlorine molecule. Because the two chlorine atoms share electrons, there is a strong force of attraction between them which holds them together. This force is called covalent bond.
Now, each chlorine atom in the chlorine molecule has the electronic configuration 2,8,8 resembling its nearest inert gas argon. Since the chlorine atoms in a chlorine molecule have inert gas electron arrangements, therefore, a chlorine molecule is more stable than two separate chlorine atoms.

Question 24:
(a) Giving one example each, state what are (i) ionic compounds, and (ii) covalent compounds.
(b) Compare the properties of ionic compounds and covalent compounds.
Solution :
(a) (i) The compounds containing ionic bonds are known as ionic compounds. They are formed by the transfer of electrons from one atom to another.
Example: Sodium chloride, NaCl.
(ii) The compounds containing covalent bonds are known as covalent compounds. They are formed by the sharing of electrons between atoms. Example: Methane, CH 4 .
(b)
Ionic compounds
(i) Ionic compounds are usually crystalline solids.
(ii) Ionic compounds have high melting and boiling points.
(iii) Ionic compounds are usually soluble in water.
Covalent compounds
(i) Covalent compounds are usually liquids or gases.
(ii) Covalent compounds have low melting and boiling points.
(iii) Covalent compounds are usually insoluble in water.

Question 25:
Explain why :
(a) covalent compounds have generally low melting points.
(b) ionic compounds have generally high melting points.
Solution :
(a) Covalent compounds have generally low melting points because they are made up of electrically neutral molecules. So, the force of attraction between the molecules of a covalent compound is ve ry weak. Hence, only a small amount of heat energy is required to break these weak molecular forces.
(b) Ionic compounds are made of up of positive and negative ions. There is a strong force of attraction between the oppositely charged ions, so a lot of heat energy is required to break this force of attraction and melt or boil the ionic compound. Due to this, ionic compounds have high melting points.

Question 26:
(a) Give two general properties of ionic compounds and two those of covalent compounds.
(b) State one test by which sodium chloride can be distinguished from sugar.
Solution :
(a) Ionic compounds:
(i) They have high melting and boiling points.
(ii) They are usually soluble in water.
Covalent compounds:
(i) They have low melting and boiling points.
(ii) They are usually insoluble in water.
(b) An aqueous solution of sodium chloride conducts electricity but a sugar solution does not conduct electri city.

Question 27:
(a) Explain why, ionic compounds conduct electricity in solution whereas covalent compounds do not conduct electricity .
(b) Which of the following will conduct electricity and which not ?
MgCl₂, CCl₄, NaCl, CS₂, Na₂S Give reasons for your choice.
Solution :
(a) Ionic compounds conduct electricity in solution because they are made up of electrically charged ions but covalent compounds are made u p of electrically neutral molecules so they do not conduct electricity.
(b) Conduct electricity: MgCl 2 , NaCl, Na 2 S (Ionic compounds)
Do not con duct electricity: CCl 4 , CS 2 ( Covalent compounds) .

Question 28:
(a) Name one ionic compound containing chlorine and one covalent compound containing chlorine.
(b) How will you find out which of the water soluble compound A or B is ionic ?
Solution :
(a) Ionic co mpound: Sodium chloride, NaCl.
Cova lent c ompound: Carbon tetrachloride, CCl 4
(b) Out of A and B, the compound whose aqueous solution cond ucts electricity will be an ionic compound.

Question 29:
Explain why, a solution of cane sugar does not conduct electricity but a solution of common salt is a good conductor of electricity.
Solution :
Common salt is an ionic compound containing ionic bonds whereas cane sugar is a covalent compound containing covalent bonds. Since, ionic compounds conduct electricity and covalent compounds do not, hence common salt is a good conductor of electricity and cane sugar is a non-conductor of electricity.

Question 30:
Give the formulae of the compounds that would be formed by the combination of the following pairs of elements :
(a) Mg and N₂ (b) Li and O₂
(c) Al and Cl₂ (d) K and H
Solution :
(a) Mg 3 N 2
(b) Li 2 O
(c) AlCl 3
(d) KH

Question 31:
(a) What are noble gases ? What is the characteristic of the electronic configuration of noble gases ?
(b) What is the cause of chemical bonding (or chemical combination) of atoms of elements ?
Solution :
(a) There are some elements in group 18 of the periodic table which do not combine with other elements. These elements are helium, neon, argon, krypton, xenon and radon . They are know