Bihar Board Class 10 Science Solutions Chapter 3 Metals and Non-metals

 

Bihar Board Class 10 Science Chapter 3 Metals and Non-metals InText Questions and Answers

ln text Questions (Page 40)

Question 1.
Give an example of a metal which
(i) is a liquid at room temperature;
(ii) can be easily cut with a knife;
(iii) is the best conductor of heat;
(iv) is a poor conductor of heat.
Answer:
(i) Mercury.
(ii) Sodium.
(iii) Silver.
(iv) Astatine is the poorest conductor of heat among all metals.
Its conductivity is less than even some non-metals like graphite.

Question 2.
Explain the meanings of malleable and ductile.
Answer:

• Malleable: Some metals can be beaten into thin sheets.
• This property is called malleability.
• Ductile : The ability of metals to be drawn into thin wires is called ductility.

Intext Questions (Page 46)

Question 1.
Why is sodium kept immersed in kerosene oil?
Answer:
Sodium reacts with oxygen and moisture at room temperature. But, it neither react nor dissolves in kerosene. So, odium is kept under kerosene.

Question 2.
Write equations for the reactions of –
(i) iron with steam
(ii) calcium and potassium with water.
Answer:
(i) 2Fe + 3H2O → Fe2O3+ 3H2
(ii) Ca + 2H2O → Ca(OH)2 + H2
2K + H2O → 2KOH + H2 + Heat energy.

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

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

1. Which is the most reactive metal?
2. What would you observe if B is added to a solution of Copper(U) sulphate?
3. Arrange the metals A, B, C and D in the order of decreasing reactivity.

Answer:

1. Metals B is most reactive.
2. Displacement reaction.
3. Metal B > metal A> metal C > metal D.

Question 4.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4
Answer:
Hydrogen gas is evolved along with salt of the metal.
Fe + H2CO4 → Fe2 SO4 + H2

Question 5.
What would you observe when zinc Is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Answer:
Zinc will displace iron from iron (ll) sulphate.
Zn + FeSO4 → ZnSO4 + Fe

Intext Questions (Page 49)

Question 1.
(i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?
Answer:

Question 2.
Why do ionic compounds have high melting points?
Answer:
The molecules of ionic compounds are bounded by strong electrostatic force.

Intext Questions (Page 53)

Question 1.
Define the following terms:

1. Mineral
2. Ore
3. Gangue.

Answer:

1. Mineral : The elements or compounds which occur naturally in the earth’s crust are known as minerals.
2. Ore : At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.
3. Gangue : Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.

Question 2.
Name two metals which are found in nature in the free state.
Answer:
Gold, platinum.

Question 3.
What chemical process is used for obtaining a metal from its oxide?
Answer:
Reduction by carbon.

Intext Questions (Page 55)

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

In which cases will you find displacement reactions taking place?
Answer:

Question 2.
Which metals do not corrode easily?
Answer:
Metals low in activity series, like gold, silver, etc. do not corrode easily.

Question 3.
What are alloys?
Answer:
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Bihar Board Class 10 Science Chapter 3 Metals and Non-Metals Textbook Questions and Answers

Question 1.
Which of the following pairs will give displacement reactions :
(а) NaCl solution and copper metal
(b) MgCl2 solutiop and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal
Answer:
(d) AgNO3 solution and copper metal.

Question 2.
Which of the following methods is suitable for preventing an iron frying pan from rusting.
(а) applying grease
(b) applying paint
(c) applying a coating of zinc
(d) all of the above
Answer:
(c) applying a coating of zinc

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
(c) silicon
(d) iron
Answer:
(a) Calcium

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

Question 5.
You are given a hammer, a battery, a bulb, wires and a switch.
(а) 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.
Answer:
(a) We will make a circuit as shown in the figure.

If with the test material, the bulb glows on turning the switch on, the materia1 is likely to be a metal.
(b) The method is pretty useful except for graphite which is a good conductor of electricity although it is a non-metal.

Question 6.
What are amphoteric oxides ? Give two examples of amphoteric oxides.
Answer:
The oxides which react with both acids and bases to give salt are called amphoteric oxide.
For example, aluminium oxide reacts in the following manner with acids and bases :

Other amphoteric oxide is zinc oxide.

Question 7.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer:
Metals that displace hydrogen : Magnesium, zinc.
Metals that do not displace hydrogen : Copper, gold.

Question 8.
In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer:
In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. The apparatus is set up as shown in figure. On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas the insoluble impurities settle down at the bottom of the anode and are known as anode mud.

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

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 the figure on the next page.

(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.
Answer:
(a) (i) No effect on diy litmus paper.
(ii) Turns blue litmus red in moist state.
(b) S + O2 → SO2

Question 10.
State two ways to prevent the rusting of iron.
Answer:
(i) Galvanisation : In this method, a coating of zinc is given on the iron article.
(ii) Painting : In this method, a coating of paint is given on the iron article.

Question 11.
What type of oxides are formed when non-metals combine with oxygen?
Answer:
Basic and amphoteric.

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.
Answer:
(a) Platinum, gold and silver are very less reactive and do not corrode. They also possess very brilliant lustre. So, they are used in jewellery.
(b) Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.
(c) Aluminium does not corrode and is a very good conductor of heat.
(d) It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates must be concerted into metal oxides.

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

Question 14.
Differentiate between metal and non-metal on the basis of their chemical properties.
Answer:

• Ion formation : Metals form positive ions and non-metals form negative ions.
• Acidic nature : Metals form basic oxides and non-metals form acidic oxide.
• Reaction with water : Metals react with water but non-metals do not.

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 o^ the solution he had used ?
Answer:
The solution the used was aqua regia.

Question 16.
Give the reason why copper is used to make hot water tanks but steel (an alloy of iron) is not.
Answer:
Hot iron reacts with steam formed by boiling water. But, copper deos not react with water.

Bihar Board Class 10 Science Chapter 3 Metals and Non-Metals Textbook Activities

Activity 3.1 (Page 37)

Question 1.
Take samples of iron, copper, aluminium and magnesium. Note the appearance of each’sample.
Answer:
They appear a little shiny.

Question 2.
Clean the surface of each sample by rubbing . them with sand paper and note their appearance again.
Answer:
They appear very shiny.

Activity 3.2 (Page 37)

Question 1.
Take small pieces of iron, copper, aluminium, and magnesium. Try to cut these metals with a sharp knife and note your observations.
Answer:
They are very hard to cut. Hold a piece of sodium metal with a pair of tongs.

CAUTION : Always handle sodium metal with care. Dry it by pressing between the folds of a filter paper. Put it on a watch glass and try to cult it with a knife.

Question 2.
What do you observe ?
Answer:
Sodium can be cut easily with knife.

Activity 3.3 (Page 38)

Take pieces of iron, zinc, lead and copper. Place any one metal on a block of iron and strike it four or five times with a hammer. Repeat with other metals.

Question 1.
Record the change in the shape of these metals.
Answer:
The metals take the form of sheets on beating.

Activity 3.4 (Page 38)

Question 2.
Consider some metals such as iron, copper, aluminium, lead, etc.
Which of the above metals are also available in the form of wires ?
Answer:
Iron, copper and aluminium.

Activity 3.5 (Page 39)

• Take an aluminium or copper wire. Clamp this wire on a stand, as shown in Fig. 3.1.
• Fix a pin to the free end of the wire using wax.
• Heat the wire with a spirit lamp, candle or a burner near . the place where it is clamped.
  

Question 1.
What do you observe after some time ?
Answer:
The wax melts and the pin falls down.

Question 2.
Note your observations. Does the metal wire melt ?
Answer:
No.

Activity 3.6 (Page 39)

• Set up an electric circuit as shown in Fig. 3.2.
• Place the metal to be tested in the circuit between terminals A and B as shown.
  

Question 1.
Does the bulb glow ? What does this indicate ?
Answer:
Yes, the bulb glows. This indicates that metals are good conductors of electricity.

Activity 3.7 (Page 39)

Question 1.
Collect samples of carbon (coal or graphite), sulphur and iodine. Carry out the activities 3.1 to 3.6 with these non-metals and record your observations.
Answer:
Table 3.1

Activity 3.8 (Page 40)

Question 1.
Is the product formed on burning magnesium acidic or basic ?
Answer:
Basic.

Question 2.
Is the product formed on burning sulphur acidic or basic ?
Answer:
Acidic.

Question 3.
Can you write equations for these reactions ?
Answer:
2Mg + O2 → 2MgO
MgO + H2O →  Mg(OH)2
S.+ O2 → SO2
SO2 + H2O → H2SO4

Activity 3.9 (Page 41)

CAUTION : The following activity needs a teacher’s assistance. It Would be better if students wear eye protection.

• Hold any of the samples taken above with a pair of tongs and try burning over a flame. Repeat with the other metal samples.
• Collect the product if formed.
• Let the products and the metal surface cool down.

Question 1.
Which metals burn easily ?
Answer:
Magnesium.

Question 2.
What colour did you observe when the metal burnt?
Answer:
Blue.

Question 3.
How does the metal surface appear after burning?
Answer:
Silvery white.
Arrange the metals in the decreasing order of their reactivity towards oxygen.

Question 4.
Are the products soluble in water ?
Answer:
Na > Mg > A1 > Zn > Fe > Pb > Copper.
Oxides of aluminium, copper, iron, lead, Mg and Zn are not soluble.Sodium oxide is soluble in water.

Activity 3.10 (Page 42)

CAUTION : This activity needs the teacher’s assistance.

• Collect the samples of the same metals as in activity 3.9.
• Put small pieces of the samples separately in beakers half filled with cold water.

Question 1.
Which metals reacted with cold water ? Arrange them in the increasing of reactivity with cold water.
Answer:
Sodium, potassium and calcium. Their increasing order of reactivity is calcium < potassium < sodium.

Question 2.
Did any metal produce fire on water ?
Answer:
Yes, sodium and potassium. ,

Question 3.
Does any metal start floating after some time ?
Answer:
Calcium.

• Put the metals that did not react with cold water in beakers half-filled with hot water.
• For the metals that did not react with hot water, arrange the apparatus as shown in Fig. 3.3 and observe their reaction with steam.

Question 4.
Which metals did not even react with steam?
Answer:
Lead, copper, silver and gold do not react with water (steam) at all.

Question 5.
Arrange the metals in the decreasing order of reactivity with water.
Answer:
Sodium > potassium > calcium > magnesium > aluminium > iron > lead > copper > silver > mercury.

Activity 3.11 (Page 44)

Collect all the metal samples except sodium and potassium again. If the samples are tarnished, rub them clean with sand paper.

CAUTION : Do not take sodium and potassium as they react vigorously even with cold water.

• Put the samples separately in test tubes containing dilute hydrochloric acid.
• Suspend thermometers in the test tubes, so that their bulbs are dipped in the acid.
• Observe the rate of formation of bubbles carefully.

Question 1.
Which metals reacted vigorously with dilute hydrochloric acid?
Answer:
Magnesium.

Question 2.
With which metal did you record the highest temperature ?
Answer:
Magnesium.

Question 3.
Arrange the metal in the decreasing order of reactivity with dilute acids.
Answer:
Mg > A1 > Zn > Ze.

Activity 3.12 (Pages 44-45)

• Take a clean wire of copper and an iron nail. Put the copper wire in a solution of iron sulphate and the iron nail in a solution of copper sulphate taken in test tubes (Fig. 3.4).
• Record your observations after 20 minutes.
  

Question 1.
In which test tube did you find that a reaction has occurred ?
Answer:
In test tube where iron nail is dipped in CuSO4 solution.

Question 2.
On what basis can you say that a reaction has actually taken place?
Answer:
Change of colour of the solutoin and depositon of copper.

Question 3.
Can you correlate your observations for the activities 3.9, 3.10 and 3.11 ?
Answer:
Yes. Fe is more reactive than copper.

Question 4.
Write a balanced chemical equation for the reaction that has taken place.
Answer:
Fe + CuSO4 → FeSO4 + Cu

Question 5.
Name the type of reaction.
Answer:
Displacement raction.

Activity 3.13 (Page 48)

• Take samples of sodium chloride, potassium iodide, barium chloride or any other salt from the science laboratory.
• Take a small amount of a sample on a metal spatula and heat directly on the flame (Fig. 3.7). Repeat with other samples.
  
• Try to dissolve the samples in water, petrol and kerosene.
• Make a circuit as hown in Fig. 3.8 and insert the electrodes into a solution of one salt.
• Test the other salt samples too in this manner.
  

Question 1.
What is the physical state of these salts ?
Answer:
Solid.

Question 2.
Did the salt impart any colour to the flame ?
Answer:
Yes.

Question 3.
Do these compound melt ?
Answer:
No.

Question 4.
Make a circuit as shown in Fig. 3.8 and insert the electrodes into a solution of one salt. What did you observe ?
Answer:
The bulb glows. This shows that the salt solution conducts electricity.

Question 5.
What is your inference about the nature of these compounds ?
Answer:

• Ionic compounds are solid and hard.
• Ionjc compounds have high melting and boiling points.
• These are soluble in water but in soluble in organic solvent such as kerosene, petrol.
• Ionic compounds in the solid state do not conduct electricity because movement of ions in the solffl is not possible due to their rigid structure. But ionic compounds* conduct electricity in the molten state.

Activity 3.14 (Page 53)

• Take three test tubes and place clean iron nails in each of them.
• Label these test tubes A, B and C. Pour some water in test tube A and cork it.
• Pour boiled distilled water in test tube B, add about 1 mL of oil and cork it. The oil will float on water and prevent the air from dissolving in the water.
• Put some anhydrous calcium chloride in test tube C and cork it. Anhydrous calcium chloride will absorb the moisture, if any, from the air. Leave these test tubes for a few days and then observe (Fig. 3.14).
  
  Fig. 3.14. Investigating the conditions under which iron rusts. In tube A, both air and water are present. In tube B, there is no air in the water. In tube C, the air is dry.

Question 1.
What do you observe ?
Answer:
Iron nails rust in test tube A, but they do not rust in test tubes B and C.

Question 2.
What is the reason behind it?
Answer:
In the test tube A, the nails are exposed to both air and water. In the test tube B, the nails are exposed to only water, and the nails in test tube C are exposed to dry air.

Question 3.
What does this tell us about the conditions under which iron articles rust ?
Answer:
Both air and moisture are necessary for rusting.

Bihar Board Class 10 Science Chapter 3 Metals and Non-Metals NCERT Exemplar Problems

Short Answer Type Questions

Question 1.
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 can he identify the produced gas. Write chemical equations for both the reactions.
Answer:
The produced gas can be identified by bringing a burning matchstick near the reaction vessel, a pop sound will be produced, which confirms the presence of hydrogen gas.
M + 2NaOH → Na2MO2 + H2
M + 2HCl → MCl2 + H2
The element is a metal

Question 2.
During extraction of metals, electolytic 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,
(c) In this electrolytic cell, where do We get pure silver after passing electric current?
Answer:
(a) Anode : Impure silver
Cathode : Pure silver
(b) Electrolyte : Silver salt, such as AgNO3, AgCl etc.
(c) We get pure silver at cathode

Question 3.
Why should the metal sulphides and carbonates K be converted to metal oxides in the process of extraction of metal from them? ‘
Answer:
The metal sulphides and carbonates should be converted to metal oxides in the process of extraction of metal from them ; because it is easier to obtain metal from its oxide, as compared from its sulphides and carbonates.

Question 4.
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
Answer:
It is because HNO3 is a strong oxidising agent. It oxidises the H2 to produced HgO.

Question 5.
Compound X and aluminium are used to join railway tracks, (a) Identify the compound X. (b) Name the reaction, (c) Write down its reaction.
Answer:
(a) X – Fe2O3
(b) Thermite reaction
(c) Fe2O3(s) + 2Al(s) → 2Fe(l) + Al2O3(s) + Heat

Question 6.
When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.
Answer:
When Na (X) metal is treated with cold watej, it gives the basic salt NaOH (Y) and liberates the gas H2 (Z) which easily catches fire.
The reaction involved here is :
2Na + H2O → 2NaOH + H2 + Heat energjr

Question 7.
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.
Answer:
‘X’ is carbon, as it is a non-metal which exists in two different forms diamond (Y) and graphite (Z). Diamond (Y) is v
the hardest natural substance, whereas graphite (Z) is a good conductor of electricity.

Question 8.
The following reaction takes place when aluminium po,wder is heated with MnO2
3MnO2(s) + 4 Al(s) → 3Mn(Z) + 2Al2O3(D + Heat
(a) Is aluminium getting reduced? (b) Is MnOz getting oxidised?
Answer:
(a) No, because oxygen is added to aluminium therefore it is getting oxidised
(b) No, since manganese has lost oxygen therefore, it is getting reduced.

Question 9.
What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?
Answer:
Solder is an alloy of lead and tin. Low melting point of solder makes it suitable for welding electrical wires..

Question 10.
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 HCl and NaOH.
Answer:
The Al (A) metal is used in thermite process, which when heated with oxygen gives an oxide Al2O3 (B).
Al2O3 is amphoteric in nature
Reaction of Al2O3 (B) with HCl :
Al2O3 + 6HCl → 2AlCl3 + 3H2O.
Reaction of Al2O3 (B) with NaOH :
Al2O3 + 2NaOH → 2NaAlO2 + H2O

Question 11.
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 reactipn involved.
Answer:
Metals low in activity series can be obtained by reducing their sulphides or oxides by heating. Mercury is the only metal that exists as liquid at room temperature. It can be obtained by heating cinnabar (HgS), the sulphide ore of mercury.
The reactions are as follows:

Question 12.
Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements.
(a) Mg and N2
(b) Li and O2
(c) Al and Cl2
(d) K and O2
Asnwer:
(a) Mg3N2
(b) Li2O
(c) AlCl3
(d) K2O

Question 13.
What happens when
(a) ZnCO3 is heated in the absence of oxygen?
(b) a mixture of Cu2O and Cu2S is heated?
Answer:
(a) When ZnCO3 is heated in the absence of oxygen it undergoes calcination. The chemical reaction can be given as

(b) When a mixture of Cu2O and Cu2S is heated it undergoes auto reduction forming copper and sulphur dioxide

Question 14.
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?
Answer:
(a) A is carbon, B is carbon monoxide and C is carbon dioxide.
(b) A belongs to Group – 14 of the Periodic Table.

Question 15.
Give two examples each of the metals that are good conductors and poor conductors of heat respectively.
Answer:
(a) Good conductor : Ag and Cu
(b) Poor conductor : Pb and Hg

Question 16.
Name one metal and one non-metal that exist in liquids state at room temperature. Also name two metals having melting point less than 310 K (37°C).
Answer:
Metal – Mercury (Hg);
Non-metal – Bromine (Br)
Two metals with melting points less than 310 K are Cesium (Cs) and GalKum (Ga)..

Question 17.
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, B and C and give the reactions involved. .
Answer:
‘A’ is Ca; ‘B’ is Ca (OH)2 and ‘C’ is GaO. The element , Ca ‘A’ reacts with water to form a compound Ca (OH)2 ‘B’ which is used in white washing. The compound Ca (OH)2 ‘B’ on heating forms CaO ‘C’ which on treatment with water gives back Ca (OH)2 ‘B
The reactions involved here are :
Ca(s) + 2H2O → Ca(OH)2(aq) + H2(g)

Question 18.
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.
Answer:
Na (A) is an alkali metal which gives the compound NaOH (B), having molecular mass = 40, on reacting with water. The compound NaOH (B) gives NaAlO2 (C), a soluble compound, on treatment with Al2Og.
The reactions involved here are :
2Na + 2H2O → 2NaOH + H2
Al2O3 + 2NaOH → 2NaAlO2 + H2O

Question 19.
Give the reaction involved during extraction of zinc from its ore by
(a) roasting of zinc ore
(b) calcination of zinc Ore
Answer:

Question 20.
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.
Ans. Cu (M) does not liberate hydrogen from acids but reacts with oxygen to give CuO, a black coloured product.
Reaction of Cu and 02 is as follows :
2Cu + O2 → 2CuO

Question 21.
An element forms an oxide A2Oa which is acidic in nature. Identify A as a metal or non-metal.
Answer:
Since an oxide of element is acidic in nature, therefore, A will be a non-metal.

Question 22.
A solution of CuSO4 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.
Answer:
Fe is more reactive as compared to Cu. Therefore, Fe displaces Cu from CuSO4 and forms FeSO4.
Fe + CuSO4 → FeSO4 + Cu

Long Answer Type Questions

Question 23.
A non-metal A which is the largest constituent of air, when heated with H„ in 1 : 3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O2 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?
Answer:
(a) A is N2; B is NH3; C is NO.and D is HNO3 because . the non-metal N2 (A) is the largest constituent of air, which when heated with H2 in 1 : 3 ratio in the presence of catalyst (Fe) gives NH3(B). N2, on heating with O2 gives NO (C).

If NO is passed into water in the presence of air it gives HNO3 (D) which acts as a strong oxidising agent. .
(b) N2 (element A) belongs to Group-15 of the Periodic Table.

Question 24.
Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.
Answer:

Question 25.
Explain the following
(a) Reactivity of Al decreases if it is dipped in HNO3
(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.
Answer:
(a) Reactivity of Al decreases if it is dipped in HNO3 due to the formation of layer of oxide, i.e.; Al2O3 on the surface of Al.
(b) Carbon cannot reduce the oxides of Na or Mg because carbon is less reactive than Na and Mg.
(c) Solid NaCl has rigid structure in which movement of ions is not possible and without the movement of free ions conduction of electricity is not possible. In aqueous solution or molten state of NaCl, the ions car move freely which can conduct electricity.
(d) Iron articles are galvanised i.e., a coating of Zn is given k on iron articles, to prevent them from corrosion.
(e) Metals like Na, K, Ca and Mg are never found in their free state in nature because they are very reactive and readily react with air and water and form compounds.

Question 26.
(i) Given below are the steps for extraction of copper from its ore. Write the reaction involved.
(а) Roasting of copper (I) sulphide
(b) Reduction of copper (I) oxide with copper (I) sulphide.
(c) Electrolytic refining
(ii) Draw a neat and well labelled diagram for electrolytic refining of copper
Answer:
(i) (a) Roasting of sulphid e ore

This reaction is known as auto-reduction

(c) Reaction for electrolytic refining .
At cathode : Cu2+(aq) + 2e2- → Cu(s)
At anode : Cu(s) → Cu2+(aq) + 2e2-
(ii) Diagram for electrolytic refining of copper

Question 27.
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.
Answer:
X is alkali metal, Na or K Y is alkaline earth metal, Mg or Ca Z is Fe Increasing reactivity series: Na > Mg > Fe

Question 28.
Afi 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.
Answer:
A is Na; B is Cl2, C is NaCl and D is NaOH because Na (A) burns with golden flame in air. It reacts with Cl2 (B). whose atomic number is 17, to give NaCl (C). An aqueous solution of NaCl (C) on electrolysis gives NaOH (D) and liberates hydrogen.

The reaction involved here are :
2Na + Cl2 → 2NaCl
2XaCl(aq) + 2H2O(Z) → 2NaOH(aq) + Cl2(g) + H2(g)

Question 29.
Two ores A and B were taken. On heating ore A gives CO2 whereas, ore B gives SO2. What steps will you take to convert them into metals?
Answer:
Since ore A gives CO2 and ore B gives SO2. Therefore, ores are MCO3 and MS.
A can be obtained by following these steps :

Metal from B can be obtained by following these steps: