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Science Answer the questions.[Che-3M]

Metals and Non-Metals · CBSE STD 10 (CBSE - English Medium). 37 questions.

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Answer the questions.[Che-3M]

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Question 13 Marks
You are given a dry cell, a torch bulb with holder, wires and crocodile clips. How would you use them to distinguish between samples of metals and non-metals?
Answer
We would create an apparatus using dry cell, a torch bulb fitted in a holder and some connecting wires with crocodile clips and connect them to make an electric circuit. Then insert a piece of sulphur between the crocodile clips and the bulb does not light up at all. This means that sulphur does not allow the electric current to pass through it. Now insert a piece of copper between the crocodile clips and the bulb will light up. This observation shows that non metals (ex- sulphur) do not conduct electricity and metals (ex- copper) conduct electricity.
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Question 23 Marks
What type of bonding would you expect between the following pairs of elements?
  1. Calcium and Oxygen.
  2. Carbon and Chlorine.
  3. Hydrogen and Chlorine.
Answer
  1. Ionic bonding.
  2. Covalent bonding.
  3. Covalent bonding.
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Question 33 Marks
What is the difference between a cation and an anion? How are they formed? Give the names and symbols of one cation and one anion.
Answer
A positively charged ion is known as cation. A cation is formed by the loss of one or more electrons by an atom.
For example: sodium loses 1 electron to form a sodium ion, Na+, which is a cation.
A negatively charged ion is known as anion. An anion is formed by the gain of one or more electrons by an atom.
For example: A chlorine atom gains (accepts) 1 electron to form a chloride ion, Cl–, which is an anion.
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Question 43 Marks
What is the action of water on (a) sodium (b) magnesium, and (c) aluminium? Write equations of the chemical reactions involved.
Answer
  1. Sodium reacts vigorously with cold water forming sodium hydroxide and hydrogen gas.

$2\text{Na(s)}+2\text{H}_2\text{O(l)}\rightarrow2\text{NaOH(aq)}+\text{H}_2\text{(g)}+\text{Heat}$

  1. Magnesium reacts with hot water to from magnesium hydroxide and hydrogen.

$\text{Mg(s)}+2\text{H}_2\text{O(l)}\rightarrow\text{Mg(OH)}_2\text{(aq)}+\text{H}_2\text{(g)}$

  1. Aluminium reacts with steam to form aluminium oxide and hydrogen gas.

$2\text{Al(s)}+3\text{H}_2\text{O(g)}\rightarrow\text{Al}_2\text{O}_3\text{(s)}+3\text{H}_2\text{(g)}$

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Question 53 Marks
What is a thermite reaction? Explain with the help of an equation. State one use of this reaction.
Answer
The reduction of a metal oxide to form metal by using aluminium powder as a reducing agent is called a thermite reaction.
This property of reduction by aluminium is made use of in thermite welding for joining the broken pieces of heavy iron objects like girders etc.
A mixture of Iron (III) oxide and aluminium powder is ignited with a burning magnesium ribbon. Aluminium reduces iron oxide to produce iron metal with the evolution of a lot of heat. Due to this heat, iron metal is produced in the molten state.
This molten iron is then poured between the broken iron pieces to weld them (to join them).
$\text{Fe}_2\text{O}_3(\text{s})+2\text{Al(s)}\rightarrow2\text{Fe(l)}+\text{Al}_2\text{O}_3\text{(s)}+\text{Heat}$
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Question 63 Marks
What are noble gases? What is the characteristic of the electronic configuration of noble gases?
Answer
There are some elements in group 18 of the periodic table which do not combine with other elements. These elements are helium, neon, argon, krypton, xenon and radon . They are known as noble gases or inert gases because they are unreactive.
If we look at the electronic configuration of noble gases, we would notice that except helium, all other inert gases have 8 electrons (helium has 2) in their outermost shells. This is considered to be the most stable arrangement of electrons.
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Question 73 Marks
Using electron-dot diagrams which show only the outermost shell electrons, show how a molecule of oxygen, O2, is formed from two oxygen atoms. What name is given to this type of bonding? (At. No. of oxygen = 8)
Answer
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Question 83 Marks
Using electron-dot diagrams which show only the outermost shell electrons, show how a molecule of nitrogen, N, is formed from two nitrogen atoms. What name is given to this type of bonding? (Atomic number of nitrogen is 7)
Answer
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Question 93 Marks
The electronic configurations of three elements X, Y and Z are as follows:

X 2, 4

Y 2, 1

Z 2, 1

  1. Which two elements will combine to form an ionic compound?
  2. Which two elements will react to form a covalent compound?

Give reasons for your choice.

Answer
  1. Y and Z will form an ionic compound because an ionic bond is formed when one of the atoms can donate electrons to achieve the inert gas configuration, and the other atom needs electrons to achieve the inert gas configuration. Since Y has 7 and Z has 1 electron in their outermost shell, they would form an ionic bond.
  2. X and Y will react to form a covalent compound because a covalent bond is formed when both the reacting atoms need electrons to achieve the inert gas electron arrangement.
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Question 103 Marks
The electronic configurations of three elements A, B and C are as follows:
A 2, 8, 1
B 2, 8, 7
C 2, 4
  1. Which of these elements is a metal?
  2. Which of these elements are non-metals?
  3. Which two elements will combine to form an ionic bond?
  4. Which two elements will combine to form a covalent bond?
  5. Which element will form an anion of valency 1?
Answer
  1. A is a metal.
  2. B and C are non-metals.
  3. A and B combines to form an ionic bond.
  4. B and C combines to form a covalent bond.
  5. B will form an anion with valency 1 since it needs only 1 electron to complete its octet.
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Question 113 Marks
The electronic configurations of four particles A, B, C and D are given below:
A 2, 8, 8
B 2, 8, 2
C 2, 6
D 2, 8
Which electronic configuration represents:
  1. Magnesium atom?
  2. Oxygen atom?
  3. Sodium ion?
  4. Chloride ion?
Answer
  1. B : Magnesium atom (At. no. = 12)
  2. C : Oxygen atom (At. no. = 8)
  3. D : Sodium ion (E.C = 2, 8)
  4. A : Chloride ion (E.C = 2, 8, 8)
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Question 123 Marks
State any three differences between the physical properties of metals and non-metals.
Answer
Difference between metals and non-metals:

Metals

  1. Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
  2. Metals are ductile i.e. they can be drawn into thin wires.
  3. Metals are good conductors of heat and electricity.

Non-metals

  1. Non-metals are non-malleable i.e. they cannot be beaten into thin sheets with a hammer.
  2. Non-metals are non-ductile i.e. they cannot be drawn into thin wires.
  3. Non-metals are bad conductors of heat and electricity.
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Question 143 Marks
  1. Name a metal for each case:
  1. It does not react with cold as well as hot water but reacts with steam.
  2. It does not react with any physical state of water?
  1. When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?
Answer
  1.  
  1. Aluminium does not react with cold or hot water but it reacts with steam.
  2. Gold does not react with any physical state of water.
  1. Sodium is more reactive than calcium. The reaction between sodium and water produces a large amount of heat, which causes the evolved hydrogen to burn and catch fire. But in the reaction between calcium and water, no heat is produced and hence the evolved hydrogen does not catch fire.
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Question 153 Marks
  1. Give the names and formulae of one metal chloride and one non-metal chloride.
  2. State an important property in which these metal chloride and non-metal chloride differ.
  3. Why do they differ in this property?
Answer
  1. Sodium chloride is a metal chloride and its formula is NaCl.
    Hydrogen chloride is a non-metal chloride and its formula is HCl.
  2.  Metal chlorides are ionic chlorides, which are electrolytes that can conduct electricity. However, non-metal chlorides are covalent chlorides, which are non-electrolytes that do not conduct electricity.
  3. They differ in this property because of the bonding in the chlorides. Metal chlorides have ionic bonds but non-metal chlorides have covalent bonds.
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Question 163 Marks
Name two metals which react violently with cold water. Write any three observations you would make when such a metal is dropped into water. How would you identify the gas evolved, if any, during the reaction?
Answer
Sodium and potassium metals react violently with cold water Observations:
  1. Metal starts moving over the surface of water making a hissing sound.
  2. Metal starts reacting with water causing little explosions.
  3. Soon the metal catches fire and starts burning.
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Question 173 Marks
Metals are said to be shiny. Why do metals generally appear to be dull ? How can their brightness be restored?
Answer
Metals lose their shine or brightness on keeping in air for a long time and acquire a dull appearence due to the formation of a thin layer of oxide, carbonate or sulphide on their surface by the slow action of various gases present in air.
Brightness of metals can be restored by rubbing the dull surface of the metal object with a sand paper, then the outer corroded layer is removed and the metal object becomes shiny and bright once again.
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Question 183 Marks
How is zinc extracted from its carbonate ore (calamine)? Explain with equations.
Answer
When calamine ore is heated strongly in the absence of air i.e. calcined, it decomposes to form zinc oxide and carbon dioxide.

$\text{ZnCO}_{3}\text{(s)}\xrightarrow[]{\ \ \ \ \ \ \text{Calcination}\ \ \ \ \ }\text{ZnO}\text{(s)}\ \ \ +\ \ \text{CO}\text{(g)}\\\\\text{Zinc carbonate}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Zinc oxide}\ \ \ \ \ \text{Carbon oxide}\ \ \ \ \ \ \ \ \ \\\text{(Calmineore)}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $

Then zinc oxide is heated with carbon and zinc metal is produced.

$\text{ZnO}\text{(s)}\ \ \ \ +\ \ \text{C}\text{(s)}\ \ \ \xrightarrow{\ \ \ \ }\ \ \ \text{Zn}\text{(s)}\ \ \ +\ \ \ \text{CO}\text{(g)}\\ \text{Zinc oxide}\ \ \ \text{Carbon}\ \ \ \ \ \text{Zinc metal}\ \ \ \text{carbon monoxide}$

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Question 193 Marks
How is manganese extracted from manganese dioxide, MnO2? Explain with the help of an equation.
Answer
Manganese metal is extracted by the reduction of its oxide with aluminium powder as the reducing agent.
Thus, when manganese dioxide is heated with aluminium powder, then manganese metal is formed.
$\underset{\substack{\text {Manganese } \\ \text { dioxide }}}{ 3 MnO _2(s)}+\underset{\substack{\text { Aluminium} \\ \text { powder}}}{4 Al ( s )} \rightarrow{ } \underset{\substack{\text {Manganese } \\ \text { metal}}}{ 3 Mn ( l )}+\underset{\substack{\text { Aluminium} \\ \text { oxide}}}{2 Al _2 O _3} + Heat$
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Question 203 Marks
How is copper extracted from its sulphide ore (copper glance), Cu2S? Explain with equations of the reactions involved.
Answer
The concentrated copper (I) sulphide ore (copper glance), Cu 2 S is roasted in air when a part of copper (I) sulphide is oxidised to copper (I) oxide.
$2\text{Cu}_2\text{O(s)}+3\text{O}_2\text{(g)}\xrightarrow{\text{Rosting}}2\text{Cu}_2\text{O(s)}+2\text{SO}_2\text{(g)}$
When a good amount of copper (I) sulphide has been converted to copper (I) oxide, then the supply of air for roasting is stopped. In the absence of air, copper (I) oxide formed above reacts with remaining copper (I) sulphide to form copper metal and sulphur dioxide.
$2\text{Cu}_2\text{O(s)}+\text{Cu}_2\text{O(s)}\xrightarrow{\text{Heat}}6\text{Cu}\text{(s)}+\text{SO}_2\text{(g)}$
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Question 213 Marks
How does the method used for extracting a metal from its ore depend on the metal’s position in the reactivity series? Explain with examples.
Answer
Different methods are used for extracting metals belonging to category of highly reactive metals, moderately reactive metals and less reactive metals. This is because the extraction of a metal from its concentrated ore is essentially a process of reduction of the metal compound present in the ore.
For example: Manganese metal is obtained by the reduction of its oxide with aluminium powder and not carbon. This is because carbon is less reactive than manganese. Carbon, which is a non-metal, is more reactive than zinc and it can be placed just above Zn in the reactivity series.
Hence, carbon can reduce the oxides of zinc and all other metals below zinc to form metals.
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Question 223 Marks
How are the properties of an alloy different from those of the constitutent elements?
Answer
  1. Alloys are stronger than the metals from which they are made.
  2. Alloys are harder than the constituent metals.
  3. Alloys are more resistant to corrosion.
  4. Alloys have lower melting points than constituent metals.
  5. Alloys have lower electrical conductivity than pure metals.
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Question 233 Marks
Give the formulae of the chlorides of the elements X and Y having atomic numbers of 3 and 6 respectively. Will the properties of the two chlorides be similar or different? Explain your answer:
Answer
Formula of chloride of element X is XCl.
Formula of chloride of element Y is YCl4.
The properties of two chlorides will be different because XCl is an i onic chloride whereas YCl.
4 is a covalent chloride.
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Question 243 Marks
Explain why, a solution of cane sugar does not conduct electricity but a solution of common salt is a good conductor of electricity.
Answer
Common salt is an ionic compound containing ionic bonds whereas cane sugar is a covalent compound containing covalent bonds. Since, ionic compounds conduct electricity and covalent compounds do not, hence common salt is a good conductor of electricity and cane sugar is a non-conductor of electricity.
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Question 253 Marks
Explain why, an aqueous solution of sodium chloride is not used for the electrolytic extraction of sodium metal.
Answer
We cannot use an aqueous solution of sodium chloride to obtain sodium metal because if we electrolyse an aqueous solution of sodium chloride, then as soon as sodium metal is produced at cathode, it will react with water present in the aqueous solution to form sodium hydroxide. Hence, electrolysis of an aqueous solution of sodium chloride will produce sodium hydroxide and not sodium metal.
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Question 263 Marks
Explain why, aluminium is a highly reactive metal, still it is used to make utensils for cooking.
Answer
Aluminium begins to corrode quickly when it comes in contact with moist air. The action of moist air on aluminium metal forms a thin layer of aluminium oxide all over the metal. This aluminium oxide is very tough and prevents the metal underneath from further corrosion. Therefore, aluminium is used for making utensils irrespective of its highly reactive property as its corrosion leads to the non-corrosion of the metal in the longer run.
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Question 273 Marks
Explain the formation of a chlorine molecule on the basis of electronic theory of valency.
Answer
The atomic number of chlorine is 17, so its electronic configuration is 2, 8, 7. Chlorine atom has 7 electrons in its outermost shell and needs 1 more electron to complete its octet and become stable.
It gets this electron by sharing with another chlorine atom. So, two chlorine atoms share one electron each to form a chlorine molecule. Because the two chlorine atoms share electrons, there is a strong force of attraction between them which holds them together. This force is called covalent bond.
Now, each chlorine atom in the chlorine molecule has the electronic configuration 2, 8, 8 resembling its nearest inert gas argon. Since the chlorine atoms in a chlorine molecule have inert gas electron arrangements, therefore, a chlorine molecule is more stable than two separate chlorine atoms.
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Question 283 Marks
Explain how, a reduction reaction of aluminium can be used for welding cracked machine parts of iron. Write a chemical equation for the reaction involved.
Answer
A mixture of Iron (III) oxide and aluminium powder is ignited with a burning magnesium ribbon. Aluminium reduces iron oxide to produce iron metal with the evolution of lot of heat. Due to this heat, iron metal is produced in the molten state.
This molten iron is poured between broken iron parts of the machine to weld them (to join them).
$\text{Fe}_{2}\text{O}_{3}\text{(s)}\ \ +\ \ 2\text{Al}\text{(s)}\rightarrow2\text{Fe}\text{(l)}+\text{Al}_2\text{O}_{3}\text{(s)}+\text{Heat}$
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Question 293 Marks
Explain giving one example, how highly reactive metals (which are high up in the reactivity series) are extracted.
Answer
The highly reactive metals are extracted by the electrolytic reduction of their molten chlorides
or oxides.
Example: Sodium metal is extracted by the electrolytic reduction of molten sodium chloride. When electric current is passed through molten sodium chloride, it decomposes to form sodium metal and chlorine gas.
$2\text{NaCl}\text{(l)}\xrightarrow[]{\text{Electrolysis}}2\text{Na}\text{(s)}+ \text{cl}_{2}\text{(g)}$
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Question 303 Marks
Explain giving equation, what happens when:
  1. ZnCO3 is heated in the absence of air?
  2. A mixture of CU2O and CU2S is heated?
Answer
a. When zinc carbonate is heated strongly in the absence of air, it decomposes to form zinc oxide and carbon dioxide.
$\underset{\substack{\text { Zinc carbonate} \text { (Calamineore)}}}{ ZnCO _3(s) } \xrightarrow{ Calcination } \underset{\text { Zinc Oxide }}{ ZnO(s) } +\underset{\text { Carbon dioxide}}{ CO _2(g)}$
b. When copper (I) oxide reacts with copper (I) sulphide, it forms copper metal and sulphur dioxide.
$2 Cu _2 O ( s )+ Cu _2 S( s ) \xrightarrow{\text { Heat }} 6 Cu ( s )+ SO _2(g)$
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Question 313 Marks
Differentiate between metals and non-metals on the basis of their chemical properties.
Answer
Difference between metals and non-metals:

Metals

  1. Metals form basic oxides.
  2. Metals displace hydrogen from water.
  3. Metals displace hydrogen from dilute acids.

Non-metals

  1. Non-metals form acidic or neutral oxides.
  2. Non-metals do not react with water.
  3. Non-metals do not react with dilute acids.
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Question 323 Marks
Describe with one example, how moderately reactive metals (which are in the middle of reactivity series) are extracted.
Answer
The moderately reactive metals are extracted by the reduction of their oxides with carbon,
aluminium, sodium or calcium.
Example: When zinc sulphide (zinc blende ore) is strongly heated in air (roasted), it forms zinc oxide and sulphur dioxide. This process is called roasting. Then, zinc oxide is heated with carbon to form zinc metal. This process is termed as reduction.
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Question 333 Marks
Describe how sodium and chlorine atoms are changed into ions when they react with each other to form sodium chloride, NaCl. What is the name given to this type of bonding? (At. No of sodium = 11; At. No. of chlorine = 17)
Answer
The atomic number of sodium is 11, so its electronic configuration is 2, 8, 1. Sodium atom has only 1 electron in its outermost shell. So, the sodium atom donates one electron (to a chlorine atom) and forms a sodium ion, Na+. The atomic number of chlorine is 17, so its electronic configuration is 2, 8, 7. Chlorine atom has 7 electrons in its outermost shell and needs 1 more electron to achieve the stable 8-electron inert gas configuration. So, a chlorine atom takes one electron (from the sodium atom) and forms a negatively charged chloride ion, Cl- This type of bonding is called ionic bonding.
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Question 343 Marks
Define the terms:
  1. mineral.
  2. ore.
  3. gangue.
Answer

  1. Minerals: The natural materials in which the metals or their compounds are found in earth are called minerals.

  2. Ores: Those minerals from which the metals can be extracted conveniently and profitably are called ores.

  3. Gangue:The unwanted impurities like sand, rocky material, earthy particles etc. present in an ore are called gangue.

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Question 353 Marks
A zinc plate was kept in a glass container having CuSO4 solution. On examining it was found that the blue colour of the solution is getting lighter and lighter. After a few days, when the zinc plate was taken out of the solution, a number of small holes were noticed in it. State the reason and give chemical equation of the reaction involved.
Answer
Zinc is more reactive than copper and hence zinc displaces copper from copper sulphate solution to form zinc sulphate solution, which is of green colour, and copper. It is due to formation of the green zinc sulphate solution that the blue colour of copper sulphate gets lighter and lighter.
Zinc from the rod reacts with the solution to form zinc sulphate solution. So the plate has a number of small holes in it.
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
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Question 363 Marks
An element E forms an oxide E2O. An aqueous solution of E2O turns red litmus paper blue.
  1. What is the nature of the oxide E2O?
  2. State whether element E is a metal or a non-metal.
  3. Give one example of an element like E.
Answer
  1. Basic oxide.
  2. Metal.
  3. Sodium,Na.
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Question 373 Marks
A metal combines with a non-metal by the transfer of electrons to form a compound Y.
  1. State the type of bonds in Y.
  2. What can you say about its melting point and boiling point?
  3. Will it be a good conductor of electricity?
  4. Will it dissolve in an organic solvent or not?
Answer
  1. Ionic bond.
  2. High melting point and boiling point.
  3. Yes.
  4. No.
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