CBSE Solutions for Class 10 English

જવાબ : The metal atoms generally have one, two or maximum of three valence electrons which they will easily lose to make cations or positive ions.

જવાબ : Iron (Fe) is additionally covered with a layer of its oxide (Fe2O3) when kept exposed to air for an extended time.

જવાબ : Traces of hydrogen sulphide (H2S) gas are present in air/atmosphere. It slowly reacts with silver to make silver sulphide which is black. As a result, silver ornaments lose their shine after sometime.

જવાબ : The black coloured compound is copper (II) oxide or cupric oxide. The metal ‘X’ is copper.
Previous Year Question Papers for CBSE Class 10 Science Chapter 3 Metals and Non-metals 1

જવાબ : Alloys are generally the mixture of two or more metals. Since metals are good conductors of electricity, a mixture of metals i.e., alloy is predicted to be a far better conductor of electricity than the pure metal,

જવાબ : It will gain two electrons.

જવાબ : Two neutral oxides are : carbon monoxide gas (CO) and laughing gas (N2O).

જવાબ : Zinc blende is zinc sulphide (ZnS) while galena is lead sulphide (PbS).

જવાબ : Gallium (Ga) may be a metal with very low freezing point (302 K). Diamond (carbon) may be a non-metal with very high freezing point . (4000 K)
Metal lead (Pb) may be a poor conductor of electricity whereas graphite (carbon) may be a good conductor of electricity.

જવાબ : A plate of impure metal acts as anode within the electro-refining of metals.

જવાબ : Bond formed is ionic or electrovalent.

જવાબ : The high melting points of salts are thanks to their closely packed structures and also thanks to stronger forces of attraction within the oppositely charged ions.

જવાબ : Metals gold (Au) and platinum (Pt) exist within the free or native state.

જવાબ : 3MnO2(s) + 4Al(s) ————> 3Mn(l) + 2Al2O3(s)

જવાબ : No, because water has no dissolved oxygen in it.

જવાબ : Mercury (Hg) is employed in amalgams that also are alloys in nature.

 

જવાબ : Silver (Ag) is that the best conductor of electricity.

જવાબ : The conductivity of metals is thanks to the movement of electrons. These are mobile even within the solid state.

જવાબ : When metals are kept exposed to air for sometime, oxygen present in air slowly combines with the metal to make metal oxide. it's deposited as a layer on the surface of metals. they seem to be dull.

જવાબ : Solid State : Sulphur, phosphorus;
Gaseous state : Nitrogen, oxygen.

જવાબ : Aluminium foils are used for the aim .

જવાબ : Graphite, an allotropie sort of carbon conducts electricity.

જવાબ : The main ore of iron is haematite (Fe2CO3) while that of aluminium is bauxite (Al2O3.2H2O).

જવાબ : German silver is an alloy of copper, zinc and nickel. It doesn't contain any silver in it.

જવાબ : Constituents of brass are copper and zinc while those of bronze are copper and tin.

જવાબ : Zinc evolves hydrogen more readily than iron on reacting with dilute HCl because it's placed above iron within the reactivity series.

જવાબ : The process is named Froth Floatation process.

જવાબ : Rust is hydrated oxide and its formula is Fe2O3.xH2O.

જવાબ : Calcination is carried within the absence of air while roasting is completed in more than air.

જવાબ : Aluminium (Al) is the most abundant metal in the earth’s crust and is present to the extent of 8-1 per cent by mass.

જવાબ : Answer: gangue

જવાબ : Answer: electronegative

જવાબ : covalent

જવાબ : Answer: froth flotation process

જવાબ : acidic

જવાબ : leaching

જવાબ : Zinc

જવાબ : high

જવાબ : Calcination

જવાબ : Sodium Oxide and Potassium oxide

જવાબ : Sodium, Potassium

જવાબ :  Diamond

જવાબ : metallurgy

જવાબ : Hydrogen

જવાબ : Magnesium

જવાબ : Iodine

જવાબ : losing electrons

જવાબ : Graphite

જવાબ : Gallium, Caesium

જવાબ : Gallium, Caesium

જવાબ : metals, non-metals

જવાબ : Metals high up in the series are obtained by electrolytic reduction because these metals are strong reducing agents and therefore, cannot be obtained by chemical reduction.
Metals in middle of series are less reactive and can be obtained by chemical reduction. The same process can not be used for both of them as highly reactive metals can not be obtained by chemical reduction.
Extraction of sodium is done by electrolysis of molten sodium chloride.

જવાબ : (a) It is because ‘Mg’ is stronger reducing agent than carbon.
(b) Sodium is obtained from molten NaCl by electrolysis.

Blister Copper is purified by electrolytic refining.

જવાબ :

જવાબ : (a) Roasting: It is a process in which sulphide ore is heated in the presence of oxygen to convert into oxide.

Cali ination: It is a process in which carbonate ore is heated in the absence of air to form oxide.

By reduction process, Zn can be extracted from its ore.

(b) Aluminium, Magnesium.

જવાબ : (a) Ag₂S (silver sulphide) is formed on silver, basic copper carbonate CuCO₃. CU(OH)₂ is formed on copper.
(b) The process of coating zinc over iron is called galvanisation. It is used to prevent rusting of iron.
(c) Alloy is a homogeneous mixture of two or more metals. One of them can be non-metal. Alloys are prepared by melting two or more metals together.
(?) Iron does not rust on adding small,quantity of carbon.
(ii) When we form alloy of iron with nickel and chromium, we get stainless steel which is malleable and does not get rusted.

જવાબ : (a) For the labelled diagram,

(b) An aqueous solution of copper sulphate containing a small amount of sulphuric acid is used as the

જવાબ : (a) We know that zinc oxide (ZnO) is of amphoteric nature. The metal zinc also behaves similarly. It reacts with both acids and alkalies. For example,

(b) Molecular mass of base Y = 40 Atomic mass of X = 40 – (16 + 1) = 23
The metal X is sodium (Na). The salt Y is NaOH and liberated gas Z is, hydrogen.

જવાબ : (a) (i) Oxides of less reactive metals can be reduced either by auto-reduction or upon heating. For example,

(ii) Oxides of moderately reactive metals can be reduced with coke. This is known as smelting. For example,

જવાબ : (a) Copper is isolated from its sulphide ore known as copper glance (Cu₂S) by heating with excess of air or oxygen.

Cuprous oxide (Cu₂O) acts as reducing agent and this process is known as auto-reduction.
(b) These metals (K, Na, Ca, Mg etc.) can be isolated by carrying out the process of electrolysis (electrolytic reduction) from their molten salts.
(c) The green coating is of basic copper carbonate. It is formed as follows :

જવાબ : (a)

1. Mercury (Hg) is liquid at room temperature :
2. Sodium (Na) is kept immersed in kerosene for storing.
3. Aluminium (Al) is malleable and ductile
4. Silver (Ag) is the best conductor of heat.

(b) The process is known as electro-refining. For the electro-refining of copper,
The conversion of a crude metal into pure metal is known as metal refining.
The refining can be done in a number of ways but the most common among these is the electro-refining and is discussed.
This method is commonly used for the purification of the metals like Cu, Ag, Zn, Ni etc. The impure metal is converted into a block which is made anode in an electrolytic cell in which a plate of pure metal acts as the cathode as shown in the Figure 3.16.
The electrolyte is the solution of the soluble salt of the same metal, preferably a double salt. On passing electric current, metal ions from the electrolyte are reduced to the metal which is deposited on the cathode. An equivalent amount of the pure metal from the anode gets oxidised and the metal ions (or cations) go into the solution. This keeps on till the whole of the metal from the anode dissolves and deposits on cathode, leaving behind impurities in the form of a mud called anode mud.

For example, in the electro-refining of crude copper, impure metal is made anode and a plate of pure copper acts as the cathode. These are connected through a battery in the external circuit as shown in the figure. The electrolyte is aqueous solution of copper sulphate containing a small amount of sulphuric acid. On passing current, the following changes occur.

જવાબ : (a) For distinction between calcination and roasting,

For the sulphide ores, the process of roasting is commonly used. It is carried by heating the ore helow its melting point with excess of air. As a result, the sulphide ore is converted to its oxide form. For example,

(b) Cracked railway lines can be joined or welded with the help of thermit welding. Thermit is a mixture of ferric oxide and aluminium powder. The chemical equation involved is :

(c) In the electrolytic refining of copper ;
Anode : A rod of impure copper.
Cathode : A rod of pure copper.
Electrolyte : An aqueous solution of copper sulphate containing a small amount of sulphuric acid.

For the sulphide ores, the process of roasting is commonly used. It is carried by heating the ore helow its melting point with excess of air. As a result, the sulphide ore is converted to its oxide form. For example,

(b) Cracked railway lines can be joined or welded with the help of thermit welding. Thermit is a mixture of ferric oxide and aluminium powder. The chemical equation involved is :

(c) In the electrolytic refining of copper ;
Anode : A rod of impure copper.
Cathode : A rod of pure copper.
Electrolyte : An aqueous solution of copper sulphate containing a small amount of sulphuric acid.

જવાબ :

1. Zinc is placed above copper in the activity series. Therefore, it can easily displace copper from copper sulphate solution.
   Zn(s) + CuSO₄(aq) ————> ZnSO₄(aq) + Cu(s)
2. Air contains traces of hydrogen sulphide (H₂S) gas. Silver has a tendency to combine with H₂S to form silver sulphide (Ag₂S) which is black in colour. On account of this, silver articles become black after some time when kept exposed to air.
3. A metal sulphide is normally converted into oxide by heating with excess of air or oxygen. This process is called roasting. Actually, the oxide of metal which is formed cap be easily reduced to the metallic form by reduction with carbon or some electropositive element. For example,
   

જવાબ : (a) For definition of corrosion: The process of slow eating up of a metal by the gases and water vapours present in air due to formation of certain chemical compounds. Corrosion of iron is known as rusting.
(b) Coating deposited on the surface of silver metal is of silver sulphide (Ag₂S). It is black in colour. The coating deposited on copper surface is of basic copper carbonate Cu(OH)₂CuCO₃. It is green in colour.

(c) Corrosion of metals particularly the rusting of iron is very harmful. The structures made from iron are generally placed in the open. These are slowly corroded or rusted. This reduces their strength gradually. They become prone to accidents and are therefore, quite dangerous. A lot of care and money is involved in their maintenance. However, corrosion of aluminium has advantage. The metal placed high in the activity series is quite reactive. It combines with the oxygen present in air to form aluminium oxide (Al₂O₃).

જવાબ :

1. Take a small amount of sulphur powder on a spatula.
2. Now burn this powder by placing a tube in a inverted position over the spatula as shown in the figure.
3. The fumes produced as a result of burning of sulphur will get collected in the tube.
4. Place the tube in vertical position and immediately add some water to it.
5. Shake the tube so that the fumes may completely dissolve.
6. Add a few drops of blue litmus to a portion of the solution. It will acquire red colour which shows that it is of acidic nature.
7. To another portion, add a few drops of red litmus solution. No colour change will be noticed. This shows that the solution is not acidic.
   

Explanation : Sulphur burns in air to form sulphur dioxide which escapes from the tube as fumes with pungent and suffocating smell. The gas produced readily dissolves in water to form sulphurous acid (H₂SO₃). The solution is therefore, acidic. It will change the colour of blue litmus to red.

જવાબ :

1. In a glass beaker, take small amount of solid sodium chloride.
2. Dip two graphite rods (electrodes) in the solution.
3. Connect these rods to a battery through a bulb and a switch.
4. Switch on the battery. The bulb will not glow. This show that no current has passed through the solid sodium chloride.
5. Now, add some water to the salt so that it may dissolve.
6. Repeat the operation. The bulb will immediately glow showing that current has passed through the salt solution.
   

જવાબ : (a) Both iron (Fe) and magnesium (Mg) will evolve hydrogen on reacting with dilute hydrochloric acid. These are active metals and are placed above hydrogen in the activity series. As copper is placed below hydrogen in the series, it will not evolve hydrogen.
(b) Surfaces of some metals acquire a dull appearance when exposed to air for a long time and they lose their lustre. This is due to the formation of layer of oxides, hydroxides, carbonates etc. on the surface For example, surface of aluminium metal becomes dull white due to the formation of coating oi aluminium oxide (Al₂O₃). Similarly, the surface of copper acquires a greenish colour since a layer oi basic copper carbonate with the formula Cu(OH)₂CuCO₃ is deposited on the surface.

જવાબ :

1. The available information suggests the metal is copper. In open air, its is oxidised to form copper (II) oxide which is black in colour. The reaction is known as oxidation reaction. On passing hydrogen gas over the hot substance, the original colour of the metal is regained. It is an example of reduction reaction.
2. The balanced chemical equations for the reactions are :
   

જવાબ : The available information suggests that the gas B is CO₂ since it turns lime water milky. The compound A is the carbonate or bicarbonate of some metal (e.g. calcium earbonate) The equations for the reactions involved are given :

જવાબ : Yes, the statement is true. We can have an idea about the relative positions of these metals in the reactivity series. For example,
(a) Sodium reacts violently even with cold water and with air or oxygen it readily combines.
(b) Magnesium reacts with hot water and with air or oxygen upon heating.
(c) Iron reacts with steam only and with air it reacts very slowly
This shows that the relative positions of these metals in the activity series are : sodium, magnesium,

જવાબ : (a) In a glass tube, take about 10 mL of aqueous solution of zinc sulphate. It is colourless. Dip a small and dry piece of magnesium ribbon in the solution. It slowly dissolves and greyish mass gets deposited at the bottom of the tube. This shows that magnesium is more reactive than zinc or it is placed above zinc in the activity series.

(b) Copper lies below hydrogen in the reactivity series and cannot lose electrons to H⁺ ions of the acid. This means that hydrogen gas cannot be liberated.

જવાબ : (a) we discover that zinc occupies a way higher position within the acitivity series as compared to copper. it's expected to displace copper present within the solution of its salt (e.g. CuSO4).

(b)

1. Blue colour of copper sulphate solution would slowly disappear.
2. No change would be noticed.

(c) Sodium combines with hydrogen to form sodium hydride.

જવાબ : (a)

Aluminium oxide (Al₂O₃) is another amphoteric oxide.
(b) Water soluble hydroxides of metals are known as alkalis. For example, NaOH.

જવાબ : Metals are electropositive in nature. Their atoms readily lose electrons to make positive ions. The electrons are accepted by H+ ions of the acid to evolve hydrogen gas. for instance ,
Zn(s) ———-> Zn2+(aq) + 2e– ;
2H+(aq) + 2e– ————> H2(g)
Non-metals are electronegative in nature. this suggests that their atoms can take up electrons and can't lose them. Therefore, they are doing not evolve hydrogen on reacting with dilute acids.

જવાબ : The ore of zinc aside from flowers of zinc (zincite) is zinc carbonate (calamine). it's the formula ZnCO3 Calamine is converted into flowers of zinc by calcination i.e., by heating strongly within the absence of air.

જવાબ : 1. The concentration of ore are often done by gravity separation method.
2. The concentration of ore is completed by Froth Floatation process.
An amalgam of mercury with silver or gold called dental alloy is employed to fill cavities within the teeth.

જવાબ : Zinc lies above mercury within the activity series and may easily replace it from mercury chloride solution. Mercury formed within the reaction gets deposited on the surface of zinc to offer it a silvery look.

But zinc is placed below magnesium in the activity series. Therefore, no chemical reaction occurs between zinc and magnesium sulphate solution.

જવાબ : Copper lies above silver within the activity series. this suggests that copper is more reactive than silver. Therefore, copper had replaced silver from AgNO3 solution. Silver got deposited on the copper plate and altered to black after sometime because silver and also some salts of silver are sensitive to light. They readily become blackish on standing or on exposure to air.

જવાબ : Titanium is called strategic metal because it is used for making certain war equipments. The properties which make the metal so special are :

1. It is light in weight but at the same time stronger than the other metals.
2. It is not affected by corrosion even if kept in the open for a very long time.

જવાબ : (a) Iron lies above copper within the activity series. this suggests that iron or iron knife will displace copper from copper sulfate solution. As a results of the reaction, ferrous sulphate are going to be formed and therefore the solution are going to be light green in colour.

(b) The bronze medal is an alloy and the constituting metals are copper and tin.
The loss of lustre by the medal is due to the formation of a coating of green layer. This layer is at basic copper carbonate.

જવાબ : In the earth’s crust, metals are present within the sort of minerals and there are quite one mineral for a specific metal. However, metal might not be extracted from all of them. The mineral from which a metal are often profitably and conveniently extracted is understood as ore. This clearly means all ores are minerals but all minerals aren't ores. for instance , the various minerals of iron are :
Haematite : Fe2O3 ;
Limonite : Fe2O3.3H2O;
Siderite : FeCO3 ;
Iron pyrites : FeS2
Iron is extracted from haematite (Fe2CO3). Haematite mineral is that the ore of iron while other minerals aren't the ores.

જવાબ :

(i) (D)
(ii) (A)
(iii) (B)
(iv) (C)
(v) (E)

જવાબ :

 Caesium
 Corrosion
 Ore
 Sodium

જવાબ :

Alloy

Brass

Sonorous
Iodine