Metal and Nonmetal class 10th Solved Questions

Question: Why is froth floatation process selected for concentration of the sulphide ore?

Ans. : Sulphide ore particles are welted by oil (pire oil) and gangue particles by water]

Question: Why cannot Al be reduced by carbon?

Ans. Aluminium is stronger reducing agent than carbon and therefore, cannot be reduced by it.

Question: Name the common elements present in the anode mud in electrolytic refining of copper. Why are they so present?

Ans. The anode mud in the electrolytic refining of copper contains antimony, selenium tellurium, silver, gold and platinum. These are present as impurities in blister copper. They are less reactive and are not affected by CuSO4-H2SO4 solution and hence settle down near anode as anode mud.

Question: Which is the cheapest and most abundant reducing agent which is used in, the extraction of metals?

Ans. Carbon in the form of coke.

Question: What is the significance of leaching in the extraction of aluminium ?

Ans. The principal ore of aluminium is bauxite (Al203). It contains Si02, iron oxides, titanium oxide as impurities. The significance of leaching in the extraction of aluminium from bauxite is to remove the impurities from the ore.

Question: What is the role of graphite rod in the electrometallurgy of aluminium?

Ans. The graphite rod is useful in the electrometallurgy of aluminium for reduction of alumina to aluminium. ;  

    

 2Al203+ 3C → 4Al + 3C02

Question: Write chemical reactions taking place in the extraction of zinc from zinc blende.

Ans. (i) The concentrated zinc blende ore (ZnS) is roasted in the presence of excess air about

120⁰  to convert it to zinc oxide.

2ZnS                  +         3O2    →    2ZnO            +         2S02

Zinc blende                                        Zinc oxide

(ii) Zinc oxide is reduced to zinc by heating with crushed coke at 1673 K

ZnO + C →Zn + CO

(iii) The impure copper is refined by electro refining method. In this method, the impure zinc is made anode and a plate of pure zinc is made cathode in an electrolytic bath containing zinc sulphate and a small amount of  dilute H2SO4. On passing current, the following reaction occur:

At anode: Zn →  Zn2+ + 2e-

At cathode: Zn2+ + 2e- →Zn

The zinc gets deposited on cathode and is collected.   

Question: What are the different methods of the purification of metals

Answer: 

PURIFICATION OR REFINING OF METALS

The metal obtained by any of the above methods is impure and is known as crude metal. The process of purifying the crude metal is called refining. The method of refining depends upon the nature of the metal and the impurities which are present in the metal. Some of the methods generally applied for refining metals are discussed below.

Liquation: 

This process is used for refining the metals having low melting points. Such as tin, lead, bismuth. etc. this is based on the principle that the metal to be refined is easily fusible (melt easily) but the impurities do not fuse easily. In this process, the impure metal is placed on the sloping hearth of the furnace and is gently heated. The hearth is maintained at a temperature slightly above the melting point of the metal. The metal melts and flows down to the bottom of sloping hearth and the impurities are left behind. The pure metal is collected to the bottom of the sloping hearth. 

Distillation:
This method is used for the purification of volatile metals (which form vapours readily). Such as mercury and zinc. In this method the impure metal is heated strongly in a vessel (called retort). The pure metal distils over and its vapours  are condensed separately in a receiver to get pure metal. The non- volatile impurities are left behind in the retort.

Oxidation method (Oxidative refining):

This method is used for the refining of metal in those cases in the impurities have greater tendency to get oxidised than metal itself.
For example: Impure iron (Pig or cast iron) is refined oxidative refining method. Pig iron contains carbon, sulphur, phosphorous, silicon and manganese as impurities. When a blast of air is blown over molten pig iron these impurities are oxidised to their oxides (CO2, SO2, P2O5 etc.) and get removed. The pure iron is left behind. Similarly, Silver is refined by this method.

Electrolytic refining:

This is the most widely method for the refining of impure metals. Many metals such as copper, zinc, tin, nickel, silver, gold etc. are refined electrolytically. It is based upon the phenomenon of electrolysis, in this process, the impure metal is made of the anode and a thin strip of pure metal is made of the cathode. A solution of the metal salt is used as an electrolyte. On passing the electric current through the electrolyte. The pure metal from the anode dissolved into electrolyte. An equivalent amount of pure metal gets deposited on the cathode. The soluble impurities go into the solution, whereas, the impurities settle down at the bottom of the anode and are known as anode mud.

For example: In the electrolytic refining of copper (The apparatus is set up as shown in figure as below) crude copper is made the anode, a thin sheet of pure copper is made the cathode. The electrolyte is a solution of copper sulphate containing a small amount of dilute H2SO4 acid. On passing the electric current copper dissolve from the anode into the electrolyte. An equivalent amount of copper is deposited at the cathode in the from pure at metal. The following reactions occurs at the electrodes.

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Electrolytic reduction of highly electropositive metals like Na, K, Mg, Ca, Al, (10th class)

The oxides of the highly electropositive metals like Na, K, Mg, Ca, Al, etc., cannot be reduced easily with carbon at moderate temperatures. For reduction, a very high temperature is required at which the metal may combine with carbon to form a carbide. These metals are thus extracted by the electrolysis of their oxides, hydroxides or chlorides in fused state. Sometimes, a small amount of some other salt is added as to lower the fusion temperature or to increase the conductivity or both. The metal is liberated at the cathode. Sodium is obtained by the electrolysis of fused mixture of NaCl and CaCl2 (Down's process) or by electrolysis of fused sodium hydroxide (Castner's process).

Extraction of Na from NaCl

At cathode    Na⁺ + e^-  --->Na

At anode    2Cl^-  ---> Cl₂ + 2e^-

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MULTIPLE CHOICE QUESTIONS

Q.1-which of the following metals will not react with oxygen,even when heated very strongly in air?

(a) Zn               (b) Al                           (c)Ag                          (d)Fe

Ans- Ag

Q.2-electrometallurgical process is employed to extract?

(a)Fe                (b)Pb               (c)Na              (d)Ag

Ans –  Na

Q.3-which of the following elements occurs in free in nature

(a)Co              (b)Fe                (c)Ni                (d)Pt

Ans-(d) Pt

Q.4-What is not true about calcinations?

(a)to remove all organic matter                        (b)to convert ore into metal (c)  to remove moisture from the ore               (d)to decompose carbonates and hydroxides

Ans-(b)to convert ore into metal.

Q.5 what is not true about roasting?

(a)to convert sulphides into oxides      (b)to remove volatile impurities (c) to dry the ore                                  (d)to convert the the ore into fine powder

Ans-(d) to convert ore into fine powder

Q.6 which of the following pairs will give displacement reaction

(a)NaCl solution and copper metal                              (b)MgCl2 solution and aluminium metal (c) FeSO4 solution and silver metal                             (d)AgNO3 solution and copper metal

Ans-(d) AgNO3 solution and copper metal

Q.7-A non-metallic oxide which is neutral in nature is

(a)CO2                        (b)CO                          (c) P2O5                      (d)none of these

Ans-(b)CO

Q.8. An iron nail is dipped in copper sulphate solution. It is observed that

(a). The colour 0f the solution remain unchanged .     (b) The colour 0f the solution becomes red . (C)The colour 0f the solution turns to light green .     (d)  None of these

Ans:- (C)

Q.9. SO2

(a).  turns dry blue litmus paper red                 (b). turns moist blue litmus paper red (C)turns moist red litmus paper blue                (d)  none of these

Ans:- (b)

10. Metal A when dipped in solution of salt of metal B ,then metal B is displaced . this shows that

(a).  Metal A is more reactive than metal B           (b)Metal B is more reactive than metal A (C) Metal A and metal B are equally reactive       (d) None of

Ans:- (a).

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Short Answer Type Questions:- (3 marks)

Q.1:- Write suitable example, explain how a metal low in the activity series can be extracted?

Ans:- Metals low in the activity series are less reactive. The oxides of these metals can be reduced to metals by heating alone. For example, extraction of Mercury (Hg) from Cinnabar (HgO).

2HgS(s) + 3O2(g) heat--------à   2HgO(s) + 2SO2(g)

2HgO(s) heat ---------------à   2Hg(l) + O2(g)

Q.2:- Write three properties of ionic compounds.

Ans:- (i) Ionic compounds have high melting points. (ii) Ionic compounds are soluble in water. (iii) Ionic compounds conduct electricity in aqueous and molten state.

Q.3. What is anodizing? What is its use?

Ans. The process of forming a thick oxide layer of aluminium oxide that makes it resistant to further corrosion.

Q.4. What is aqua regia? What is its use?

Ans. Aqua regia is a mixture of conc. HCl and conc. HNO3 in the ratio 3:1. It can dissolve gold and platinum.

Q.5. What do you mean by thermite reaction? What is its use?

Ans. The reaction between Iron(II) oxide Fe2O3 with Al is used to join rail track joints or cracked machine parts. This reaction is known as thermit reaction.

Fe2O3 (s) + 2Al (s) 2Fe (l) + Al2O3 (s) + Heat

Q.6. Why active metals do not liberate H2 gas when treated with dil. HNO3?

Ans. This is because HNO3 is strong oxidizing agent. It oxidizes H2 produced to water and itself gets reduced to nitrogen oxides.

Q.7. Sometimes the ore itself acts as a reducing agent. Give an example.

Ans. During roasting of Cu2S, the ore itself acts as a reducing agent.

2CuS (s) + 3O2(g)         --------→ 2Cu2O(s) + 2SO2(g)

2Cu2O + Cu2S              -----------→ 6Cu(s) + SO2(g)

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2 marks questions (short answer type question)

Q.1:- Name two metals that react with dil.HNO3 to evolve H2 gas ?

Ans:- magnesium and manganese

Q.2:- What would you observe when zinc is added to a solution of iron(II) sulphate ?write the chemical reaction that takes place.

Ans:- The solution of iron(II) sulphate slowly turns to colourless and grey coloured layer of Fe is deposited on the surface of zinc metal. Zn(s) + FeSO4(aq) ------->ZnSO4(aq) + Fe(s)

Q. 3:- Why ionic compounds have high melting points?

Ans:- Ionic solids have crystalline structure in which there is strong interionic attraction. So large amount of energy is needed to overcome this force of attraction.

Q. 4:- What do you mean by roasting? How it is different from calcination? In which types of ores roasting is done?

Ans:- Heating an ore strongly in excess of air is called roasting. This is done to convert sulphide ores into its oxide form. Calcination is different from roasting because it is done in absence of air.   2ZnS(s) + 3O2(g) heat -----à 2ZnO(s) + 2SO2

Q.5:- Define :- (i) Ore, (ii) Mineral.

Ans:-   Ore:- The minerals from which an element can be extracted profitably and conveniently is called ore. E.g. - Bauxite, Al2O3.2H2O – is an ore of aluminum. Mineral:- The compounds of elements that occurs naturally in earth‘s crust are called minerals. E.g.- Glauber‘s salt Na2SO4.7H2O; Borax Na2B4O7.10H20 are two mineral sources of Sodium.

Q.6:- Name two metals which are found in nature in the Free State.

Ans:- Silver and Gold.

Q.7:- Define :- (i) Enrichment of Ores (ii) Gangue.

Ans:- (i) Removal of earthly impurities like sand, clay from an ore is called enrichment of ore. (ii) The earthy impurities like sand, clay that are found along with an ore are called gangue or matrix.

Q.8:- Write short notes on electrolytic refining of metals.

Ans:- In electrolytic refining the impure metal is taken as anode and the pure metal is taken as cathode. These two rods are dipped in aqueous salt solution of the same metal and electricity is passed. Pure metal from anode is dissolved into the solution and equivalent amount of pure metal from the electrolyte is deposited at the cathode

Q.9:- Name the conditions which are essential for corrosion.

Ans:- (i) Presence of moisture, (ii) Presence of air.

Q.10:- What is Galvanisation? Write its use.

Ans:- Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of Zinc.

X Metals and Non-Metals Solved Important Guess Questions

Metals and Non-Metals Solved Important  Guess Questions Q1. Define allotropy. Name the two common allotropes of phosphorus. Ans:  Allotropy : "Existence of an element in two or more distinct forms which have different physical properties but same chemical properties is called allotropy and the forms are called allotropes." Q.2 .Write four differences in the properties of the two allotropes of phosphorus. Ans: Two allotropes of phosphorus are white phosphorus and red phosphorus. Red phosphorus White phosphorus (i) It has an opaque red colour. (i) It is colourless, but appears yellow when kept in atmosphere. (ii) It sublimes at 400ºC. (ii) Its melting point is 44ºC. (iii) It is less reactive. (iii) It is very reactive. (iv) It combines with chlorine only on heating. (iv) It combines with chlorine spontaneously. Q.3.Why do allotropes of phosphorus show different properties? They show different properties as the bonding between yellow phosphorus is weak while in red phosphorus is strong. Q4. How does iron occur in nature?   Ans 2. Iron occurs in nature in combined states mainly it occurs in oxide and sulphide ores. Oxide-ores :    Haematite : Fe2O3    Magnetite : Fe3O4    Limonite : Fe2O3.3H2O Sulphide-ores : Iron pyrites : FeS2     Carbonate ores : Siderite : FeCO3 The various steps involved in the extraction of iron metal from its oxide ore (haematite) (Fe2O3) are given below : (i) Concentration of ore : The iron ore haematite (Fe2O3) is concentrated by crushing the ore and washing it in a stream of water. This removes most of the gangue. (ii) Calcination : The washed iron is then strongly heated in the absence of air (calcinied) to expel water sticking to it. (iii) Reduction : The iron oxide ore (haematite) is mixed with coke and lime stone and put into a blast furnace near its bottom. The following chemical reaction takes place in blast furnace : (a) Coke present in blast furnace burns insufficent air to form carbon monoxide (which acts as reducing agent) 2C (Carbon) + O2 (Oxygen) ------à  2CO (Carbon monoxide) (b) Carbon mono oxide reduces iron (III) oxide to iron metal. Fe2O3 (Iron oxide) + 3CO (Carbon mono oxide) ----à  2Fe (Iron metal) + 3CO2 (Carbon dioxide) The molten iron collects at the bottom of blast furnace. (c) The lime stone decomposes to form calcium oxide and carbon dioxide due to intense heat in the blast furnace. CaCO3 (Calcium carbonate) ---Heat-à CaO (Calcium oxide) + CO2 (Carbon dioxide) (d) This calcium oxide reacts with silicon dioxide (sand) present as impurity in the ore to form liquid calcium silicate called slag CaO (Calcium oxide) + SiO2 (Silicon dioxide) ------> CaSiO3 (Calcium silicate) The molten slag collects on the top of the molten iron and is separately taken out Q.5. State the differences between (i) iron and steel (ii) stainless steel and steel. Ans: Differences : (i) (a) Iron is an element which don't contain any impurities while steel is an alloy of iron with 1.5% of carbon (b) Pure iron is not very hard and strong while steel is very hard and strong. (ii) Stainless steel is alloy of iron with chromium and nickel while steel is alloy of iron with carbon. Q6. State the three major steps usually involved in the metallurgical processes. Ans3. The major steps usually involved in the metallurgical processes are (i) concentration of ore (ii) conversion of concentrated ore into metal oxide (iii) Reduction of metal oxide to metal (iv) Refining of impure metal. Q.7. Name the chief ore of aluminum. Describe the necessary chemical equations how aluminum is extracted from this ore. The main ore of aluminium is Bauxite(Al2O3.2H2O) The various steps involved in the extraction of aluminium metal from its bauxite ore are given below : Purification : The bauxite ore usually contains iron oxide and silica (sand) as impurities which are removed by Baeyer's method as follows : Bauxite (Al2O3)is dissolved in a hot concentrated solution of sodium hydroxide to form sodium aluminate (NaAlO2). The iron oxide and other impurities do not dissolve and are removed by filtration. Al2O3 + 2NaOH  ------>2NaAlO2 + H2O Sodium aluminate is mixed with water and cooled. This gives a precipitate of aluminium hydroxide NaAlO2  + 2H2O -------> Al(OH)3 + NaOH When aluminium hydroxide is strongly heated it gives pure aluminium oxide or alumina 2Al(OH)3 --------> Al2O3 + 3H2O (Water) Electrolytic reduction of pure aluminium oxide :  Al2O3 is reduced to aluminium in a specially made electrolytic cell as shown in Fig. given below. In this cell the inside coke lining acts as a cathode and carbon rod is used as an anode. The cell is charged with a mixture of concentrated purified Al2O3 and cryolite (Na3AlF6). Cryolite is mixed to lower down the melting temperature of alumina. When the current is passed through the cell, mixture melts because of the heat generated due to the resistance offered by the mixture. The molten mixture is then electrolysed at the bottom of the cell. Al2O3 ----Electrolysis------>2Al3+ + 3O2- The aluminium thus obtained is further purified by electrolytic refining. Q8. Describe the extraction of Cu from its ore by: (i) concentration (ii) Roasting (iii) Reduction (iv) Refining of crude metal. Ans4. The main ores of copper are copper pyrites (CuFeS2) and copper glance (Cu2S). The various steps usually involved are given below : Concentration : Concentration is done by froth-floatation. The finely powdered ore is mixed with water and pine oil in large tank. The ore particles are wetted by the oil, whereas the gangue particles are wetted by water. Air is blown through the mixture. As a result oil froth containing ore particles is formed which floats on the top of the water and can be skimmed off easily. Roasting : The concentrated ore is roasted. Roasting is done in reverberatory furnace. 2CuFeS2 + O2 -------àCu2S + 2FeS + SO2­ Cu2S and FeS are partially oxidized. 2Cu2S + 3O2 -------à 2Cu2O + 2SO2 2FeS. + 3O2 --------à 2FeO + 2SO2­ Reduction : Takes place in Bassemer converter. It can be tiled in any position. It has a basic lining inside. The little FeS present in matte is completely oxidized to FeO and then changed into slag with reaction of silica. Cuprous sulphide reacts with Cu2O to form blister copper. Cu2S + 2Cu2O --------> 6Cu + SO Refining of copper : The impure copper metal is purified by the process of electrolytic refining to get pure copper metal. The impure metal is made the anode and a strip of pure copper cathode. These are immersed in a copper sulphide solution with a little sulphuric acid added to it. On passing an electric current the anode begins to dissolve pure copper gets deposited on the cathode. The impurities either dissolves in the solution or deposited below the anode as anode mud. At anode : Cu (Copper) --------->Cu2+ (copper ion) At cathode : Cu2+ (Copper ion) -------->Cu (Copper atom) deposits on cathode Thus pure copper is obtained at the cathode.
Q9.  What is rusting of iron?
Ans5. Rusting : The process of eating away of metal, by the action of atmospheric reagents changing the metal  into its compounds is called as rusting. When iron is kept to environment, a red coloured layer is formed on its surface it is rust and the process is known as rusting. The rusting of iron is : (i) 2Fe (Iron) + O2 (Oxygen) + H2O (Water)-----à 2Fe(OH)2 (Iron hydroxide) (ii) Fe(OH)2 + O2 + H2O ------à2Fe2O3.3H2O (Rust) Necessary conditions for rusting are : (i) Presence of moisture (ii) Presence of air
10. Write any two common methods to prevent rusting.
Prevention of Rusting : (i) Rusting is prevented by galvanization. It is a process of coating Zinc metal over iron by electro plating. (ii) It is prevented by painting the surface of metal and coating the surface of metal with oil or grease