Science & Tech Part 1 Chapter 8 Metallugy Solutions

FeSO4 forms a green colour in the water.

Stainless steel is an alloy made from iron, carbon and chromium.

K2O is basic oxide.

Diamond is good conductor of heat but bad conductor of electricity.

Gold is the least reactive metal.

Aluminium: electric conductor : gold : : electric insulator

Aluminium oxide is amphoteric oxide.

The minerals from which the metal can be separated economically are called ores.

The extraction of metals from their ores by various methods of separation and further purification to obtain pure metals are involved in the branch of metallurgy.

The extraction of metals from their ores and then refining them for use is known as metallurgy.

Metals such as silver, gold and platinum are found in free state.

Metals are found in combined states as their salts such as oxides, carbonates, sulphides, and nitrates.

The unwanted impurities of soil, sand, rocky substances, etc., present in the ore are called gangue.

Atomic number of aluminium is 13 and its electronic configuration is (2, 8, 3).

Bauxite : Aluminium ore : : Cassiterite : Tin

Bauxite reacts with sodium hydroxide in the Bayer’s process- Right

Brass : Aluminium and zinc : : Bronze : Copper and tin

Bronze : Cu + Sn : : Stainless steel : Fe + Cr + C

Bronze is an alloy of copper and tin.

Explanation:

Bronze is a solid alloy composed primarily of 88% copper and 12% tin. It is used in the production of hardware, utensils musical instruments, medals, and other items. Due to its resistance to corrosion caused by seawater, it is used in submerged bearings and ship propellants.

Cassiterite is a copper ore- Wrong

Corrosion of silver causes a black layer of silver sulphide.

Diamond : electric insulator : : graphite : electric conductor

Diamond is a hard substance- Right

Electrolysis is used to obtain pure metal from impure metal- Right

Answer

Metal A with electronic configuration of (2, 8, 1) is sodium (Na).

Metal B with electronic configuration of (2, 8, 8, 2) is calcium (Ca).

Metal A is more reactive than B as it has to lose only one electron from the outermost shell while metal B has to lose two electrons, to achieve a stable electronic configuration.

Answer

Bauxite is the main ore of aluminium with silica (SiO2), ferric oxide (Fe2O3) and titanium oxide (TiO2) as impurities in it.

In this process, the bauxite ore is first crushed and then it is leached by heating with hot concentrated caustic soda (NaOH) solution under high pressure for 2 to 8 hrs at 140 to 150 °C in a tank called a digester.

Aluminium oxide, being amphoteric in nature, dissolves in an aqueous NaOH solution, forming water-soluble sodium aluminate.

\[\ce{\underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O3.2H2O_{(s)}}} + \underset{\text{hydroxide}}{\underset{\text{Sodium}}{2NaOH_{(aq)}}} -> \underset{\text{aluminate}}{\underset{\text{Sodium}}{2NaAlO_{2(aq)}}} + \underset{\text{Water}}{3H2O_{(l)}}}\]

The iron oxide present in the gangue does not dissolve in an aqueous NaOH solution and is separated by filtration.

However, silica from the gangue dissolves in an aqueous NaOH solution forming water-soluble sodium silicate.

The solution of sodium aluminate is diluted with water and then cooled to 50 °C. This gives aluminium hydroxide as a precipitate.

\[\ce{\underset{\text{aluminate}}{\underset{\text{Sodium}}{NaAlO_{2(aq)}}} + \underset{\text{Water}}{2H2O_{(l)}} -> \underset{\text{hydroxide}}{\underset{\text{Sodium}}{NaOH_{(aq)}}} + \underset{\text{hydroxide}}{\underset{\text{Aluminium}}{Al(OH)3\downarrow}}}\]

The aluminium hydroxide is then filtered, washed, dried and calcined by heating at 1000 °C to get pure aluminium oxide, called alumina.

\[\ce{\underset{\text{hydroxide}}{\underset{\text{Aluminium}}{2Al(OH)_{3(s)}}} ->[heat][1000°C] \underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O_{3(s)}}} + \underset{\text{Water vapour}}{3H2O_{(g)}}}\]

Answer

In Bayer’s process, the bauxite ore is first crushed and then it is leached by heating with hot concentrated caustic soda (NaOH) solution under high pressure for 2 to 8 hrs at 140 to 150 °C in a tank called a digester.

Aluminium oxide, being amphoteric in nature, dissolves in an aqueous NaOH solution, forming water-soluble sodium aluminate.

\[\ce{\underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O3.2H2O_{(s)}}} + \underset{\text{hydroxide}}{\underset{\text{Sodium}}{2NaOH_{(aq)}}} -> \underset{\text{aluminate}}{\underset{\text{Sodium}}{2NaAlO_{2(aq)}}} + \underset{\text{Water}}{3H2O_{(l)}}}\]

The iron oxide present in the gangue does not dissolve in aqueous NaOH solution and is separated by filtration.

However, silica from the gangue dissolves in aqueous NaOH solution forming water-soluble sodium silicate.

The solution of sodium aluminate is diluted with water and then cooled to 50 °C. This gives aluminium hydroxide as a precipitate.

\[\ce{\underset{\text{aluminate}}{\underset{\text{Sodium}}{NaAlO_{2(aq)}}} + \underset{\text{Water}}{2H2O_{(l)}} -> \underset{\text{hydroxide}}{\underset{\text{Sodium}}{NaOH_{(aq)}}} + \underset{\text{hydroxide}}{\underset{\text{Aluminium}}{Al(OH)_3↓}}}\]

The aluminium hydroxide is then filtered, washed, dried and calcined by heating at 1000 °C to get pure aluminium oxide, called alumina.

\[\ce{\underset{\text{hydroxide}}{\underset{\text{Aluminium}}{2Al(OH)_{3(s)}}} ->[heat][1000°C] \underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O_{3(s)}}} + \underset{\text{vapour}}{\underset{\text{Water}}{3H2O_{(g)}}}}\]

Answer

The process of heating carbonate ores in limited air to convert it into respective oxide is called calcination.

For example, zinc carbonate is heated strongly in a limited supply of air to convert it to zinc oxide.

\[\ce{\underset{\text{Zinc carbonate}}{ZnCO_{3(s)}} ->[Heat] \underset{\text{Zinc oxide}}{ZnO_{(s)}} + \underset{\text{Carbon dioxide}}{CO_2\uparrow}}\]

Answer

The process of slow degradation of the metals due to the attack of atmospheric gases, moisture, acids, etc. on the surface of metals is called corrosion.

Iron reacts with moist air and a deposit of reddish substance (Fe2O3.H2O) is formed on it. This substance is called rust and the corrosion of iron is known as rusting.

Carbon dioxide in moist air reacts with the surface of copper vessel. Copper loses its lustre due to formation of a greenish layer of copper carbonate (CuCO3) on its surface. This is called patination of copper.

Various methods such as galvanizing, tinning, alloying, etc. are used to protect metals from corrosion.

Answer

The unwanted impurities of sand, soil, rocky substances, etc., present in the ore are called gangue.

Ores are taken out from the mines and the gangue is usually separated from the ore at the site itself by various methods.

The process of separating gangue from the ores is called the concentration of ores.

For example, bauxite ore contains impurities of silica (SiO2), ferric oxide (Fe2O3) and titanium oxide (TiO2). These impurities are called gangue.

Answer

Most metals being reactive do not occur in nature in the free state but are found in a combined state as their salts such as oxides, carbonates, sulphides, and nitrates.

However, some unreactive metals like silver, gold, platinum, generally occur in a free state.

The compounds of metals that occur in nature along with the impurities are called minerals.

For example, bauxite is a mineral of aluminium.

Answer

There can be many minerals from which a metal can be extracted.

However, only those minerals from which a metal can be extracted profitably are called ores.

Metals can be extracted from their ores by means of various methods of separation.

Answer

The process of heating of sulphide ores strongly in excess of air to convert it into respective oxide is called roasting.

For example, zinc sulphide is heated strongly in excess of air to convert it to zinc oxide.

\[\ce{\underset{\text{Zinc sulphide}}{2ZnS_{(s)}} + 3O_{2(g)} -> \underset{\text{Zinc oxide}}{2ZnO_{(s)}} + \underset{\text{Sulphur dioxide}}{2SO_2↑}}\]

Answer

The compounds formed from two units, namely cation and anion are called ionic compounds.

The cation and anion being oppositely charged, there is an electrostatic force of attraction between them. This force of attraction between cation and anion is called as the ionic bond.

The number of cations and anions in a compound and the magnitude of the electric charge on them is such that the positive and negative charges balance each other. As a result, an ionic compound is electrically neutral.

For example, ionic compound sodium chloride (NaCl) is formed as sodium metal gives away one electron while the nonmetal chlorine takes up one electron. Na+ and Cl− ions formed are held together by attractive force called ionic bond.

Answer

Answer

Extraction of highly reactive metals:

Highly reactive metals such as sodium, magnesium and calcium are obtained by electrolytic reduction.

The metals are deposited at the cathode (negatively charged electrode), whereas chlorine gas is liberated at the anode (positively charged electrode).

E.g. For extraction of sodium metal, cathode and anode reactions are as follows:

At cathode: \[\ce{Na+ + e^- -> Na}\] (Reduction)

At anode: \[\ce{2Cl- -> Cl2 + 2e^-}\] (Oxidation)

Answer

Extraction of less reactive metals:

Less reactive metals such as gold, silver, platinum are found in a free state in nature.

However, the reserves of copper in the free state are very few. It is found mainly in the form of Cu2S. Copper is obtained from Cu2S ore just by heating in the air.

\[\ce{\underset{\text{sulphide}}{\underset{\text{Copper(I)}}{2Cu2S_{(s)}}} + \underset{\text{Oxygen}}{3O_{2(g)}} ->[Heat] \underset{\text{oxide}}{\underset{\text{Copper(I)}}{2Cu2O_{(s)}}} + \underset{\text{dioxide}}{\underset{\text{Sulphur}}{2SO2\uparrow}}}\]

\[\ce{\underset{\text{Copper(I) sulphide}}{Cu2S_{(s)}} + \underset{\text{Copper(I) oxide}}{2Cu2O_{(s)}} ->[Heat] \underset{\text{Copper}}{6Cu_{(s)}} + \underset{\text{Sulphur dioxide}}{SO_2\uparrow}}\]

The copper metal thus obtained can be further refined electrolytically.

Answer

Extraction of moderately reactive metals:

Moderately reactive metals such as iron, zinc, lead, copper usually occur in the form of their sulphide salts or carbonate.

It is easier to obtain metals from their oxides rather than sulphides or carbonates.

E.g. \[\ce{\underset{\text{Zinc sulphide}}{2ZnS_{(s)}} + 3O_{2(g)} -> \underset{\text{Zinc oxide}}{2ZnO_{(s)}} + \underset{\text{Sulphur dioxide}}{2SO2\uparrow}}\]

Carbonate ores are strongly heated in a limited supply of air to transform them into oxides. This process is called calcination.

E.g. \[\ce{\underset{\text{Zinc carbonate}}{ZnCO_{3(s)}} ->[Heat] \underset{\text{Zinc oxide}}{ZnO_{(s)}} + \underset{\text{Carbon dioxide}}{CO2}}\]

The oxide so obtained is reduced to metal by using suitable reductant such as carbon.

\[\ce{\underset{\text{Zinc oxide}}{ZnO_{(s)}} + \underset{\text{Carbon}}{C_{(s)}} ->[Heat] \underset{\text{Zink}}{Zn_{(s)}} + \underset{\text{Carbon monoxide}}{CO\uparrow}}\]

The metal thus obtained can be further refined electrolysis.

Answer

Physical nature: Ionic compounds are solids and are hard. They are generally brittle and break into pieces when pressure is applied.

Melting and boiling points: Ionic compounds have high melting and boiling points.

Solubility: Ionic compounds are generally soluble in water. However, they are insoluble in kerosene and petrol.

Electrical conductivity: Ionic compounds conduct electricity in a molten state or in its aqueous solution. Conduction of electricity in these states is due to the movement of charged particles (i.e., ions) towards the oppositely charged electrodes. However, in solid-state, ionic compounds do not conduct electricity as movement of the ions is not possible due to their rigid structure.

Answer

In the calcination process, carbonate ores are strongly heated in a limited supply of air to transform them into oxides. In this process, carbonate ores decompose to form a metal oxide and carbon dioxide gas.

Answer

In roasting process, the sulphide ores are strongly heated in air to transform them into oxides. In this process, sulphide ores are oxidized to form metal oxides and sulphur dioxide gas.

Answer

Difference between Bayer’s process and Hall’s process:

In Bayer’s process, aluminium ore is heated with concentrated caustic soda while in Hall’s process, it is heated with aqueous sodium carbonate to obtain water-soluble sodium aluminate. In Bayer’s process, the solution of sodium aluminate is diluted with water to obtain aluminium hydroxide while in Hall’s process, sodium aluminate is converted to aluminium hydroxide by reaction with CO2.

Bayer’s process:

In this process, the bauxite ore is first crushed and then it is leached by heating with hot concentrated caustic soda (NaOH) solution under high pressure for 2 to 8 hrs at 140 to 150 °C in a tank called a digester.

Aluminium oxide, being amphoteric in nature, dissolves in an aqueous NaOH solution, forming water-soluble sodium aluminate.

\[\ce{\underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O3.2H2O_{(s)}}} + \underset{\text{hydroxide}}{\underset{\text{Sodium}}{2NaOH_{(aq)}}} -> \underset{\text{aluminate}}{\underset{\text{Sodium}}{2NaAlO_{2(aq)}}} + \underset{\text{Water}}{3H2O_{(l)}}}\]

The iron oxide present in the gangue does not dissolve in an aqueous NaOH solution and is separated by filtration. However, silica from the gangue dissolves in an aqueous NaOH solution forming water-soluble sodium silicate.

The solution of sodium aluminate is diluted with water and then cooled to 50 °C. This gives aluminium hydroxide as a precipitate.

\[\ce{\underset{\text{aluminate}}{\underset{\text{Sodium}}{NaAlO_{2(aq)}}} + \underset{\text{Water}}{2H2O_{(l)}} -> \underset{\text{hydroxide}}{\underset{\text{Sodium}}{NaOH_{(aq)}}} + \underset{\text{hydroxide}}{\underset{\text{Aluminium}}{Al(OH)_3}\downarrow}}\]

The aluminium hydroxide is then filtered, washed, dried and calcined by heating at 1000 °C to get pure aluminium oxide, called alumina.

\[\ce{\underset{\text{hydroxide}}{\underset{\text{Aluminium}}{2Al(OH)_{3(s)}}} ->[heat][1000 °C] \underset{\text{oxide}}{\underset{\text{Aluminium}}{Al2O_{3(s)}}} + \underset{\text{vapour}}{\underset{\text{Water}}{3H2O_{(g)}}}}\]

Answer

Chlorine dissolves in water to form hypochlorous acid and hydrochloric acid.

\[\ce{\underset{\text{Chlorine}}{Cl_{2(g)}} + \underset{\text{Water}}{H2O_{(l)}} -> \underset{\text{Hypochlorous acid}}{HOCl_{(aq)}} + \underset{\text{Hydrochloric acid}}{HCl_{(aq)}}}\]

Answer

When dry aluminium hydroxide is calcined by at 1000 °C, pure aluminium oxide, called alumina is obtained.

\[\ce{\underset{\text{Aluminium hydroxide}}{2Al(OH)_{3(s)}} ->[heat][1000 °C] \underset{\text{Aluminium oxide}}{Al2O_{3(s)}} + \underset{\text{Water vapour}}{3H2O_{(g)}}}\]

Answer

Ferric oxide reacts with aluminium to form iron and aluminium oxide. This reaction is known as the thermit reaction.

\[\ce{\underset{\text{Ferric oxide}}{Fe2O_{3(s)}} + \underset{\text{Aluminium}}{2Al_{(s)}} ->[Ignited] \underset{\text{Iron}}{2Fe_{(l)}} + \underset{\text{Aluminium oxide}}{Al2O_{3(s)}}+Heat}\]

Answer

When magnesium is treated with dilute hydrochloric acid, it forms magnesium chloride with release of hydrogen gas.

\[\ce{\underset{\text{Magnesium}}{Mg_{(s)}} + \underset{\text{Hydrochloric acid}}{2HCl_{(aq)}} -> \underset{\text{Magnesium chloride}}{MgCl_{2(aq)}} + \underset{\text{Hydrogen}}{H2↑}}\]

Answer

Aluminium combines with oxygen to form aluminium oxide.

\[\ce{\underset{\text{Aluminium}}{4Al_{(s)}} + \underset{\text{Oxygen}}{3O_{2(g)}} -> \underset{\text{Aluminium oxide}}{2Al2O_{3(s)}}}\]

Answer

Sodium aluminate reacts with water to give aluminium hydroxide as a precipitate and sodium hydroxide.

\[\ce{\underset{\text{Sodium aluminate}}{NaAlO_{2(aq)}} + \underset{\text{Water}}{2H2O_{(l)}} -> \underset{\text{Sodium hydroxide}}{NaOH_{(aq)}} + \underset{\text{Aluminium hydroxide}}{Al(OH)_3↓}}\]

Answer

On burning, sodium metal combines with oxygen in the air to form sodium oxide.

\[\ce{\underset{\text{Sodium}}{4Na_{(s)}} + \underset{\text{Oxygen}}{O_{2(g)}} -> \underset{\text{Sodium oxide}}{2Na2O_{(s)}}}\]

Answer

Sulphur burns in air to form sulphur dioxide.

\[\ce{\underset{\text{Sulphur}}{S} + \underset{\text{Oxygen}}{O2} -> \underset{\text{Sulphur dioxide}}{SO2}}\]

Answer

Zinc carbonate is heated strongly in a limited supply of air to convert it to zinc oxide. This process is called calcination.

\[\ce{\underset{\text{Zinc carbonate}}{ZnCO_{3(s)}} ->[Heat] \underset{\text{Zinc oxide}}{ZnO_{(s)}} + \underset{\text{Carbon dioxide}}{CO_2↑}}\]

Answer

Zinc oxide is reduced to zinc by heating it with carbon.

\[\ce{\underset{\text{Zinc oxide}}{ZnO_{(s)}} + \underset{\text{Carbon}}{C_{(s)}} ->[Heat] \underset{\text{Zinc}}{Zn_{(s)}} + \underset{\text{Carbon monoxide}}{CO↑}}\]

Answer

Zinc sulphide is heated strongly in excess of air to convert it to zinc oxide. This process is called roasting.

\[\ce{\underset{\text{Zinc sulphide}}{2ZnS_{(s)}} + 3O_{2(g)} -> \underset{\text{Zinc oxide}}{2ZnO_{(s)}} + \underset{\text{Sulphur dioxide}}{2SO_2↑}}\]

Answer

Answer

Answer

The method shown in the figure is the magnetic separation method.

The magnetic separation process is based on the differences in magnetic properties of the ore components.

This method requires an electromagnetic machine which consists of a nonmagnetic conveyor belt moving over two rollers, one of which is magnetic in nature while the other is nonmagnetic.

The powdered ore is dropped over the moving belt near the nonmagnetic roller. Two collector vessels are placed below the magnetic roller.

The nonmagnetic particles are carried further along with the belt and fall in the collector's vessel placed away from the magnetic roller. At the same time, the magnetic portion of the ore is attracted by the magnetic roller and falls in the collector vessel near the magnetic roller.

Answer

Generally, nonmetals do not react with water, except halogens.

E.g. Chlorine on dissolving in water gives the following reaction:

\[\ce{\underset{\text{Chlorine}}{Cl_{2(g)}} + \underset{\text{Water}}{H2O_{(l)}} -> \underset{\text{acid}}{\underset{\text{Hypochlorous}}{HOCl_{(aq)}}} + \underset{\text{acid}}{\underset{\text{Hydrochloric}}{HCl_{(aq)}}}}\]

Extraction of moderately reactive elements is done by roasting and calcination method.

Answer

Boron

Explanation-

Boron is placed in group 13 while others are placed in group 17 of the modern periodic table.

Answer

Phosphorous

Explanation-

Phosphorus is nonmetal while others are alloys.

Answer

Brass

Explanation-

Brass is a metalloid while others are metals.

Answer

Cu

Explanation-

Copper (Cu) is a less reactive metal while others are highly reactive metals.

Answer

Sulphur

Explanation-

Sulphur is a nonmetal while others are metals.

Answer

Froth floatation

Explanation-

Froth floatation is a method used for the concentration of ores while others are methods used for the prevention of corrosion.

Answer

Calcination

Explanation-

Calcination is a process involved in extraction of carbonate ores while others are methods used for prevention of corrosion.

Answer

Corrosion can be prevented by the following methods:

Galvanizing: Galvanizing is a process of giving a thin coating of zinc on iron or steel materials to protect them from corrosion. Zinc, being more electropositive than iron, undergoes corrosion first. Thus, it prevents corrosion of iron.

However, if zinc layer goes away and the inner iron gets exposed, then the inner iron layer will start to rust.

Anodizing: The process of coating metals such as aluminium and copper with a thin and strong layer of their oxides by electrolysis is called anodizing process. For this, the copper or aluminium article is used as the anode. As this oxide layer is strong and uniform all over the surface, it is useful for the prevention of the corrosion of the metal.

Electroplating: Electroplating is the process in which a less reactive metal is coated on a more reactive metal by electrolysis. It protects the object made of reactive metal from corrosion. For example, silver-plated spoons, gold plated ornaments, etc.

Alloying: The homogenous mixture formed by mixing metal with other metals or nonmetals in a certain proportion is called an alloy Alloying helps to decrease the intensity of corrosion of metals. For example, stainless steel does not get stains with air or water and also does not rust. It is an alloy made from 74% iron, 18% chromium and 8% carbon.

Answer

Examples of alloys: Bronze and stainless steel

Answer

Aluminium oxide (Al2O3) and zinc oxide (ZnO) are examples of amphoteric oxides.

The following reactions show the amphoteric character of zinc oxide:

\[\ce{\underset{(Basic nature)}{ZnO_{(s)}} + 2HCl_{(aq)} -> \underset{Zinc chloride}{ZnCl2_{(aq)}} + H2O_{(l)}}\]

\[\ce{\underset{(Acidic nature)}{ZnO_{(s)} + 2Na}OH_{(aq)} -> \underset{Sodium zincate}{Na2ZnO2_{(aq)}} + H2O_{(l)}}\]

Gold and silver are active metals- Wrong

Halogen reacts with acid- Right

Answer

This method represents Wilfley’s table of concentration of ores.

Explanation:

Wilfley’s table is made by fixing narrow, thin and long wooden riffles on an inclined surface.

The table is given a regular vibrating motion.

The powdered ore obtained from lumps of the ore using ball mill is fed on the top of Wilfley’s table and running stream of water is also released from the upper side.

As a result, the lighter gangue particles are carried away by water and heavy ore particles in which proportion of minerals is more, settle between the wooden riffles fixed on the table and get collected on the slits between them.

Amphoteric oxide forming metal- Aluminium

Carbon allotropes- Diamond and graphite

Metal in Liquid state- Mercury

Ore of Aluminum- Bauxite

Cu, Fe, Zn, Al

In electrolytic reduction of alumina graphite is used as a cathode.

In Electrolytic reduction of alumina, Anode : Set of carbon (graphite) rods : : Cathode : Graphite lining

In preparation of Aqua regia hydrochloric acid and nitric acid acid are mixed.

In solid state, ionic compounds conduct electricity- Wrong

In the electrolytic method, a layer of highly active metal is applied to a less active metal- Wrong

In the electrolytic reduction of alumina, the lining of graphite acts as an anode- Wrong

In Wilfley table method to separate particles of gangue gravitation method is used.

Ionic compounds are electrically neutral.

Ionic compounds are soluble in kerosene- Wrong

Answer

Iron displaces copper from copper sulphate solution forming ferrous sulphate and copper.

\[\ce{\underset{\text{Iron}}{Fe_{(s)}} + \underset{\text{Copper sulphate}}{CuSO_{4(aq)}} -> \underset{\text{Ferrous sulphate}}{FeSO_{4(aq)}} + \underset{\text{Copper}}{Cu_{(s)}}}\]

Iron is less reactive than aluminium.

Mercury, silver, gold are highly reactive metals- Wrong

Metal sheets : Malleable : : Electric wires : Ductile

Answer

The method shown is an electrolytic reduction of alumina.

A set of graphite rods dipped in the molten electrolyte acts as the anode. and the graphite lining acts as a cathode.

Use of cryolite: Addition of cryolite reduces the melting point of alumina to about 1000 °C.

Anode reaction: \[\ce{2O^2+ -> O2 + 4e^-}\]

Cathode reaction: \[\ce{Al^3+ + 3e^- -> Al_{(l)}}\]

Answer

The method shown in the figure is froth floatation method.

The froth floatation process is based on two opposite properties of the particles, hydrophilic and hydrophobic.

The metal sulphide particles are hydrophobic. Due to this property, they get wetted mainly with oil. On the other hand, gangue particles are hydrophilic and get wetted by water.

This method is used to separate metal sulphide ores such as zinc blende (ZnS) and copper pyrite (CuFeS2).

Answer

The given diagram represents anodizing process used for the prevention of corrosion.

This method is used for the prevent corrosion of aluminium and copper.

In this method, copper or aluminium article is used as the anode.

Answer

The type of reaction occurring in the given diagram is displacement reaction.

\[\ce{\underset{\text{Iron}}{Fe_{(s)}} + \underset{\text{Copper sulphate}}{CuSO_{4(aq)}} -> \underset{\text{Ferrous sulphate}}{FeSO_{4(aq)}} + \underset{\text{Copper}}{Cu_{(s)}}}\]

Observations:

The blue colour of the solution will turn to green in test tube A and copper coating will form on iron nail because iron displaces copper from copper sulphate.

The reaction will not occur in test tube B because iron is more reactive than copper.

Answer

The method is called electroplating.

Explanation:

a. Electroplating is the process in which a less reactive metal is coated on a more reactive metal by electrolysis.

b. It protects the object made of reactive metal from corrosion. c.

It also improves the appearance of the object.

Silver plated spoons, gold plated ornaments are examples of electroplating.

Answer

This method is electrolytic reduction of alumina.

Anode reaction:

\[\ce{2O^{2-} -> O2 + 4e^-}\] (Oxidation)

Cathode reaction:

\[\ce{Al^{3+} + 3e^- -> Al_{(l)}}\] (Reduction)

Alumina has a very high melting point (>2000 °C). The purpose of mixing ‘cryolite’ and ‘fluorspar’ with ‘alumina’ in the electrolytic reduction of alumina is to carry out the process at a much lower temperature. Addition of cryolite and fluorspar reduces the melting point of alumina to about 1000 °C.

Two metals that react with water: Potassium, sodium

Two moderately reactive metals: Zinc, iron

1. Most highly reactive metal: Potassium
2. Most less reactive metal: Gold

Pressure cooker : Anodizing : : Silver plated spoons : Electroplating

The arrangement of metals in the increasing or decreasing order of reactivity is called the reactivity series of metals.

When an iron metal reacts with silver nitrate solution, a displacement reaction occurs.

Zinc rod reacts with silver nitrate solution to form zinc nitrate and silver.

Rusting of iron : Fe2O3 : : corrosion of copper : CuCO3

Soft metal : Na : : hard metal : Tungsten

Stainless steel is an alloy of iron.

Sulphide ores : Roasting : : Carbonate ores : Calcination

The electrolysis of alumina involves the use of fluorspar and cryolite to increase the melting point- Wrong

The minerals from which the metal can be separated economically are called ores.

The sound of one metal colliding with another makes a noise, this property is called as sonority.

To prevent corrosion of iron and steel galvanizing method is used.

The homogeneous mixture formed by mixing a metal with other metals or nonmetals in certain proportion is called an alloy.

Metals combine with oxygen to form basic oxides. Aluminium oxide and zinc oxide show the properties of both basic and acidic oxides. These oxides are known as amphoteric oxides.

Corrosion is the damage caused to the metal by the chemical reaction of air, water, and acids with the surface of the metal. Generally, reactive metals corrode easily, and non-reactive metals have good resistance to corrosion.

A certain type of reddish coloured solid layer collects on iron surface. This layer is called ‘rust’.

Answer

The reaction is as follows:

\[\ce{\underset{\text{Copper}}{Cu_{(s)}} + \underset{\text{nitrate}}{\underset{\text{Silver}}{2AgNO_{3(aq)}}} -> \underset{\text{nitrate}}{\underset{\text{Copper (II)}}{Cu(NO3)_{2(aq)}}} + \underset{\text{Silver}}{2Ag_{(s)}}}\]

When one of the metals in an alloy is mercury the alloy is called amalgam.

tinning

Answer

Answer

Answer

The device used for grinding an ore- Ball mill

Answer

In the electrolysis of alumina, graphite rod is used as anode.

During the electrolytic reduction of alumina, aluminium is produced at the cathode and oxygen gas is evolved at the anode.

This gas reacts with the graphite rods (anode) and forms carbon dioxide.

Answer

The process of coating metals such as aluminium and copper with a thin and strong layer of their oxides by electrolysis is called anodizing process.

When aluminium is anodized, a thin layer of aluminium oxide is formed all over the surface. This restricts the contact of aluminium metal with oxygen and water and prevents corrosion of aluminium.

Answer

Coins are made from metals and alloys because metals and their alloys possess the property of malleability. So, they can be hammered into flat shape without breaking.

Metals and alloys used for making coins should be corrosion resistance and bright in colour. They should also be hard and wear resistance.

Answer

Ionic compounds are composed of cations and anions.

These ions are held together by strong electrostatic forces of attraction.

Considerable amount of energy is required to break these strong forces of attraction.

Answer

Copper vessels turned greenish due to the formation of copper carbonate layer.

The citric acid present in the lemon or tamarind neutralizes the basic copper carbonate and dissolves the layer.

That is why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.

Answer

The magnetic separation process is based on the differences in magnetic properties of the ore components.

When the powdered ore is dropped over the moving belt near nonmagnetic roller, the nonmagnetic particles are carried further along with belt and fall in the collector vessel placed away from magnetic roller. At the same time, the magnetic portion of the ore is attracted by the magnetic roller and falls in the collector vessel near the magnetic roller.

Thus, magnetic separation method is used to separate the magnetic ingredients in the ores.

Answer

The greenish colour on copper vessels is due to the formation of copper carbonate on it.

Copper carbonate reacts with acids present in lemon or tamarind and as a result, this copper carbonate layer gets removed.

Answer

Silver articles turn blackish after some time of exposure to air. This is because silver undergoes corrosion when exposed to air containing hydrogen sulphide.

Silver reacts with hydrogen sulphide in air to form a layer of silver sulphide \[\ce{(Ag2S)}\], which gives silver articles a blackish appearance.

Answer

Pine oil is hydrophobic.

The particles of the metal sulphide ores which are hydrophobic get wetted by pine oil.

They float with the foam on the surface of water.

Thus, by using this property some ores which contain hydrophobic particles in them can be concentrated by froth floatation process.

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Kerosene contains sodium as:

As a highly reactive metal, sodium interacts with water in a highly exothermic manner.

It has a strong reaction with water and oxygen.

It can generate much heat when it reacts with oxygen and water vapor in the atmosphere.

To prevent this strong reaction, it is thus stored or maintained in kerosene.

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Copper pyrite- CuFeS2

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Cryolite- Na3AlF6

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Ferrous tungstate- FeWO4

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Fluorspar- CaF2

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Sodium aluminate- NaAlO2

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Stannic oxide- SnO2

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An alloy of copper and tin- Bronze

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Metals which are amphoteric in nature- Aluminium (Al), zinc (Zn)

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Method used to prevent corrosion of copper- Anodization and/or tinning

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Nonmetal which is a good conductors of electricity- Graphite

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Answer

The process of extraction of aluminium from alumina- Electrolytic reduction

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The process of strong heating of carbonate ores in insufficient air– Calcination

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The reagent which dissolves noble metals- Aqua regia

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Two highly reactive metals- Lithium (Li), sodium (Na)

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They are crystalline in nature.

They are brittle and can be broken into pieces by applying pressure.

They have high melting and boiling points.

They are good conductors of electricity in the molten state and in aqueous solutions.

They are readily soluble in water and insoluble in solvents like kerosene, petrol, etc.

Zinc sulphide : Roasting : : zinc carbonate : calcination