metals

Name any two metals that are available in their free state in nature?

                Gold and silver are available in free state in nature

3.            Identify the group and period of the following metals in the periodic table (a) copper (b) iron

a)      Copper belongs to IB group and 4^th period

b)      Iron belongs to V׀׀׀ group and 4^th period

4.            Write the electronic configuration of a copper atom?

                Its electronic configuration is 1s²2s²2p⁶ 3s²3p⁶3d¹⁰4s₁

5.            Write the electronic configuration of an iron atom?

                Its electronic configuration is 1s²2s²2p⁶3s²3p⁶3d⁶4s²

6.            Name the important ores of copper. Write their molecular formula?

                The important ores of copper are:

·         Copper pyrites (CuFeS²)

·         Copper glance (Cu₂S)

·         Cuprite (Cu₂O)

·         Malachite [CuCO₃ Cu(OH)₂]

·         Azurite [2CuCO₃ Cu(OH)₂]

7.            Name the important ores of iron. Write their molecular formula?

                The important ores of iron are:

·         Haematite (Fe₂O₃)

·         Magnetite (Fe₃O₄)

·         Limonite (Fe₂O₃H₂O)

·         Siderite (FeCCO₃)

ADDITIONAL IMPORTANT QUESTIONS

1.            Name two major sources of metals?

                Earth’s crust and seawater are major source of metals

2.            Write the atomic number and mass number of copper?

                The atomic number of copper is 29 and its mass number is 64.

3.            What is rust? Write its chemical formula?

1.       Rust is hydrated oxide of iron.

2.       Its chemical formula is Fe₂O₃2H₂O

4.            Name a metal that does not react with water under any condition?

                Copper does not react with water under any condition.

5.            Name the largest source of metals?

                The earth’s crust is the largest source of metals.

6.            Name two metals that do not react with air?

                Gold and platinum do not react with air.

7.            Name ant two transition elements?

                Copper and iron are transition elements.

8.            Name any two places in India where copper ores are found?

                Copper ores occur in India in Karnataka, Rajasthan, Sikkim and Bihar.

9.            Name the physical nature and the composition of the compound formed on copper when it is burnt in air?

                The compound is a black layer of cuprous oxide.

10.          How do you prevent of rusting of iron?

                Rusting of iron can be prevented by coating it with a layer of zinc or painting.

11.          What happens when sodium is burnt in excess of oxygen?

                When sodium is burnt in excess of oxygen, sodium peroxide is formed

                2Na+O₂⟶Na₂O₂

12.          How does iron react with dry air and pure water?

                Iron does not react in both cases

13.          What is the general product obtained when metals react with oxygen?

                Metals react with oxygen to produce respective oxides.

14.          How does magnesium react with air?

                Magnesium burns in air forming magnesium oxide. 2MG+O₂⟶2MgO

15.          What is a solid solution? How is it prepared?

1.       A solid solution is a homogenous mixture of a metal with one or more metals and nonmetals.

2.       It is prepared in molten state and solidified.

16.          How is copper oxide formed?

                When a foil of copper is burnt in a flame and allowed to cool, after sometime, a black layer is seen on the copper                 foil. This is copper oxide. 2Cu+O₂⟶2CuO

17.          Name the arrangement used to extract iron. Why is it so called? What do you call the iron extracted in it? In                 what form is it obtained?

1.       Iron is extracted using a blast furnace.

2.       It is called so because a blast of hot air is blown into it.

3.       The iron so extracted is called cast iron or pig iron.

4.       It is in molten form.

18.          Mention any two physical properties of iron?

·         Iron is a grayish white solid metal

·         In its pure form it is soft

·         It has a melting point of 1808K

·         It is a ferromagnetic substance

19.          Mention any four physical properties of copper?

·         It is a rose red heavy metal

·         It is malleable and ductile

·         It has high thermal conductivity

·         It has high melting and boiling point.

20.          Describe briefly the reaction of metals with chlorine?

·         All metals react with chlorine to form their respective chlorides.

·         More reactive metals react at room temperature, whereas less reactive metals react on heating the metal.

                Na+CI₂⟶2NaCI

                2AI+3CI₂⟶2FeCI₃

21.          How do metals react with nitric acid?

·         Metals react with very dilute nitric acid to form respective nitrates liberating hydrogen

                Mg+HNO₃⟶Mg (NO₃)₂+H₂↑

·         Metals react with moderately concentrated nitric acid to form respective nitrates liberating nitric oxide

                3Cu+8HNO₃⟶3Cu (NO₃)₂+2NO+4H₂O

·         Metals react with concentrated nitric acid to form metallic nitrates liberating nitrous oxide

                Cu+4HNO₃⟶Cu (NO₃)₂+2NO₂ ↑+2H₂O

22.          Name any three alloys of iron. Mention any two of their uses?

                The alloys of iron are:

·         Stainless steel used in utensils and surgical instruments.

·         Nickel steel used in utensils and drilling instruments.

·         Steel used pipes, nails, sheets and cutting tools.

23.          Mention any two alloys of copper and their uses?

                The alloys of copper are:

·         Brass used for making utensils, electrical appliances, machinery parts etc.

·         Bronze, used for statues, bells coins and utensils.

·         German silver used for utensils, resistance coils and ornamental wares.

·         Gun metal used for barrels of guns, gears and castings.

24.          How do metals react with water? Give two examples?

·         Metals react with water or steam to form respective oxide or hydroxides and liberating hydrogen.

·         Sodium reacts with cold water to produce sodium hydroxide liberating hydrogen.

                2Na+ H₂O⟶2NaOH+H₂↑

·         When steam is passed over hot iron, zinc or magnesium, forming respective oxide and liberating hydrogen.

                3Na+4 H₂O⟶Fe₃O₄+4H₂↑

25.          Write balanced chemical equations for the following: (a) reaction of magnesium with dilute hydrochloric acid.                 (b) Iron with dilute sulphuric acid. (c) Zinc with dilute nitric acid.

a)      Mg+2HCI⟶MgCI₂+H₂↑

b)      Fe+ H₂SO₄⟶FeSO₄+ H₂↑

c)       Zn+2HNO₃⟶Zn (NO₃)₂+H₂↑

26.          Under what conditions do the following react with water (a) magnesium (b) zinc? Write the chemical equations?

a)      Both magnesium and zinc react with water when

·         The metal is hot

·         Steam is passed over them

b)      Magnesium reacts with steam to give magnesium oxide liberating hydrogen

                Mg+H₂0⟶MgO+H₂↑

c)       Zinc reacts with steam to give zinc oxide liberating hydrogen

                Zn+H₂0⟶ZnO+H₂↑

27.          Explain briefly an experiment to demonstrate the reaction of a metal with different components of air?

·         Cut a small piece of sodium and place it on a watch glass

·         The interior surface of the metal that is shining becomes slowly dull forming sodium oxide

·         4Na+O₂⟶2Na₂O

·         Further, sodium oxide reacts with carbon dioxide to form sodium carbonate.

_·          Na₂O+CO₂⟶Na₂CO₃

·         Thus sodium oxide reacts with air to form sodium oxide first and subsequently sodium carbonate.

28.          Name the mineral acid. How do metals react with them? Give one example each?

·         Hydrochloric acid, sulphuric acid and nitric acid are mineral acids.

·         Metals react with dilute hydrochloric acid to form respective chlorides liberating hydrogen

                Mg+2HCI⟶MgCI₂+H₂↑

·         Metals react with dilute sulphuric acid to form respective sulphates liberating hydrogen

                Mg+ H₂SO₄⟶MgSO₄+ H₂↑

·         Metals react with very dilute nitric acid to form respective nitrates liberating hydrogen

                Mg+HNO₃⟶Mg (NO₃)₂+H₂↑

29.          Name the most commonly used ore for extracting copper. Describe the process of extraction in brief?

a)      Copper is extracted from its sulphides ore copper pyrites.

b)      Following are the steps involved in the extraction.

·         Concentration of the ore:

This is done by froth floatation. The finely powdered ore is mixed with pine oil and water in a large tank.

The water in the tank is agitated by blowing in air due to which froth is formed. The sulphide ore mixes with the oil and forms a thin film and the remaining particles get wetted by water and remain at the bottom.

When air is babbled through this froth particles containing the copper particles floats on the top of water and are skimmed off. Foam settles down and concentrated sulphides ore is obtained.

·         Roasting of the ore:

                The concentrated ore is roasted in air in a blast furnace. It reacts with oxygen to form copper sulphide and ferrous                 oxide

                2CuFeS₂+4O₂⟶Cu₂S+2FeO+3SO₂↑

The product is mixed with sand and heated in a furnace. Ferrous oxide forms ferrous silicate, which is removed as slag. The remaining copper sulphides is further roasted to form cuprous oxide.

FeO+SiO₂⟶FeSiO₃

2Cu₂S+3O₂ ⟶2Cu₂O+2SO₂

Supply of air is stopped. Remaining cuprous sulphides reacts with cuprous oxide and forms molten copper.

Cu₂S+2Cu₂O⟶6CU+SO₂↑

This molten copper is allowed to cool and purified to get pure copper.

30.          What is electrolytic refining? Describe the electronic refining of copper?

a)      The process of obtaining a metal of very high purity from a sample of impure metal by the process of electrolysis is called electrolytic refining.

b)      The electrolytic refining of impure copper is carried out in an electrolytic tank containing acidified copper sulphate solution as the electrolyte.

·         A thick block of impure metal is made the anode and a thin strip of pure copper is made the cathode.

·         Both the cathode and the anode are immersed in the acidified copper sulphate solution

·         On passing electric current, impure copper from the anode dissolves and goes into copper sulphate solution and pure copper from the solution deposits on the cathode.

·         The impurities collect below the anode as anode mud.

31.          Explain the process of extracting iron in brief?

a)      Iron is extracted from its oxide ore haematite. It is composed mainly of ferric oxide and silica.

b)      Following are the important steps involved.

·         Concentration: The ore is concentrated by hydraulic washing. The crushed ore is washed with a stream of water. Heavier particles settle at the bottom, while the lighter gangue is washed away.

·         Roasting: the concentrated ore is mixed with limestone and coke in the ratio 8:1:4 and is introduced into a furnace through the cup and cone arrangement at the top of the furnace.

                Hot air is blown from the bottom of the furnace.

·         Lima decomposes to form calcium oxide and carbon dioxide and further forms calcium silicate.

·         Carbon dioxide is reduced to carbon monoxide which reduces iron oxide to iron and the molten iron is collected at the bottom of the furnace as pig iron or cast iron.

32.          Write the important reactions that take place in the extraction of iron?

                Following reactions take place.

·         Due to the intense heat limestone is decomposed into calcium oxide and carbon dioxide.

                CaCO₃⟶CaO+CO₂

·         Calcium oxide formed during the reaction reacts with silicon dioxide present in the ore as impurity to form molten calcium silicate.

                CaO+SiO₂⟶CaSiO₃

·         Coke combines reacts with oxygen to form carbon dioxide.

                C+O₂⟶CO₂+Heat

·         Carbon dioxide reacts with more coke to form carbon monoxide.

                CO₂(g)+C(s)⟶2CO(g)

·         Carbon monoxide reduces iron (׀׀׀) oxide to liquid iron. The molten iron collects at the bottom of the furnace.

                Fe₂O₃+3CO⟶2Fe+3CO₂

33.          Explain the method of concentration of copper ore?

·         Copper is concentrated by froth floatation.

·         The finely powered ore is mixed with pine oil and water in a large tank.

·         The water in the tank is agitated by blowing in air due to which froth is formed.

·         The sulphide ore mixes with the oil and forms a thin film and the remaining particles get wetted by water and remains at the bottom.

·         When air is bubbled through this, froth particles containing the copper particles floats on the top of water and is skimmed off.

·         Foam settles down and concentrated sulphide ore is obtained.

34.          How does iron react with water? Write the chemical equation?

a)      Iron does not react with cold water.

b)      When steam is passed over hot iron, hydrogen gas is liberated and ferric oxide is formed.

                3Fe+4H₂O⟶Fe₃O₄+4H₂↑

35.          How do the products differ when copper reacts with moderately concentrated nitric acid and concentrated                 nitric acid? Write the balanced chemical equations?

a)      In both the cases cupric nitrate and water are formed. With moderately concentrated nitric acid copper liberates nitric oxide, where with concentrated nitric acid, copper gives nitrogen dioxide.

b)      With moderately concentrated nitric acid the reaction is as follows

3Cu+8HNO₃⟶3Cu (NO₃)₂+2NO+4H₂O

With concentrated nitric acid the reaction is as follows

Cu+4HNO₃⟶Cu (NO₃)₂+2NO↑+2H₂O