Class 10 Science Metals & Non-metals (Solved Assignment-03)

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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.

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.

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.

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