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Science Answer the questions.[Che-2M]

Metals and Non-Metals · CBSE STD 10 (CBSE - English Medium). 77 questions.

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Question 12 Marks
You can buy solid air-freshners in shops. Do you think these substances are ionic or covalent?
Why?
Answer
Solid air-fresheners are covalent compounds because they are volatile compounds with low melting and boiling points.
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Question 22 Marks
Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick?
Answer
When iron reacts with dilute sulphuric acid, it forms iron sulphate and hydrogen gas.
$\text{Fe}\text{(s)}+2\text{H}_2\text{SO}_4\text{(aq)}\rightarrow\text{FeSO}_4\text{(aq)}+\text{H}_2\text{(g)}$
When hydrogen gas is ignited with a burning matchstick, it produces a ‘pop’sound.
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Question 32 Marks
Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.
Answer
$\text{Al}_2\text{O}_3\text{(s)}+6\text{HCl(aq)}\rightarrow2\text{AlCl}_3\text{(aq)}+3\text{H}_2\text{O(l)}$
In this reaction, aluminium oxide behaves as a basic oxide because it reacts with an acid to form sait and water.
$\text{Al}_2\text{O}_3\text{(s)}+2\text{NaCH(aq)}\rightarrow2\text{NaAlO}_2\text{(aq)}+\text{H}_2\text{O(l)}$
In this reaction, aluminium oxide behaves as an acidic oxide because it reacts with a base to form sait and water.
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Question 42 Marks
With the help of examples, describe how metal oxides differ from non-metal oxides.
Answer
Metal oxides are basic in nature and turn red litmus blue. For example: Magnesium oxide. Non-metal oxides are acidic or neutral in nature. The acidic oxides turn blue litmus red.
For example: Carbon dioxide.
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Question 52 Marks
Why is white phosphorus kept immersed under water?
Answer
White phosphorus is kept immersed in water because it reacts spontaneously with oxygen of air to form phosphorus pentoxide but does not react with water.
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Question 62 Marks
Why has sodium chloride a high melting point?
Answer
Sodium chloride has a high melting point because it is an ionic compound and these compounds are made of up of positive and negative ions. There is a strong force of attraction between the oppositely charged ions, so, a lot of heat energy is required to break this force of attraction and melt or boil the ionic compound.
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Question 72 Marks
Why do gold ornaments look new even after several years of use?
Answer
Gold ornaments look new even after several years of use because gold does not corrode when exposed to atmosphere. It is a highly unreactive metal which remains unaffected by air, water vapour and other gases in the atmosphere.
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Question 82 Marks
Why does a new aluminium vessel lose shine so soon after use?
Answer
A new aluminium vessel lose shine so soon after use due to the corrosion of aluminium metal when exposed to moist air. This happens because the oxygen of air reacts with aluminium toform a thin, dull layer of aluminium oxide all over the vessel.
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Question 92 Marks
Why does aluminium not corrode right through?
Answer
Aluminium does not corrode right through because aluminium is more reactive than iron and it forms a layer of aluminium oxide as soon as it comes in contact with moist air.
This aluminium oxide layer is very tough and prevents the aluminium underneath from corroding.
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Question 102 Marks
Why are the metals like Na, K, Ca and Mg never found in their free state in nature?
Answer
The metals like Na, K, Ca and Mg never found in their free state in nature because of the reason that all of these metals are high-up in the reactivity series. And just because they are so reactive, they are never found in nature as free elements.
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Question 112 Marks
Why are aqueous solutions of ionic compounds able to conduct electricity?
Answer
An aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.
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Question 122 Marks
Which one of the methods given in column I is applied for the extraction of each of the metals given in column II:
Column I
Column II
Electrolytic reduction.
Aluminium.
Reduction with Carbon.
Zinc.
Reduction with Aluminium.
Sodium.
 
Iron.
 
Manganese.
 
Tin.
Answer
Column I
Column II
Electrolytic reduction.
Aluminium and Sodium.
Reduction with Carbon.
Zinc, Iron and Tin.
Reduction with Aluminium.
Manganese.
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Question 132 Marks
Which of the following will conduct electricity and which not?
MgCl2, CCl4, NaCl, CS2, Na2S Give reasons for your choice.
Answer
Conduct electricity: MgCl2 , NaCl, Na2S (Ionic compounds)
Do not con duct electricity: CCl4 , CS2 ( Covalent compounds).
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Question 142 Marks
Which of the following reactions will not occur? Why not?
  1. $\text{MgSO}_4\text{(aq)}+\text{Cu(s)}\xrightarrow{\ \ \ \ \ }\text{CuSO}_4\text{(aq)}+\text{Mg(s)}$
  2. $\text{CuSO}_4\text{(aq)}+\text{Fe(s)}\xrightarrow{\ \ \ \ \ }\text{FeSO}_4\text{(aq)}+\text{Cu(s)}$
  3. $\text{MgSO}_4\text{(aq)}+\text{Fe(s)}\xrightarrow{\ \ \ \ \ }\text{FeSO}_4\text{(aq)}+\text{Mg(s)}$
Answer
Reaction (a) will not occur because Cu is less reactive than Mg.
Reaction (c) will also not occur because Fe is less reactive than Mg.
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Question 152 Marks
Which of the following elements would yield:
  1. An acidic oxide.
  2. A basic oxide.
  3. A neutral oxide.
Na, S, C, K, H
Answer
  1. Acidic oxide: S, C
  2. Basic oxide: Na, K
  3. Neutral oxide: H
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Question 162 Marks
What type of oxides are formed when non-metals react with oxygen? Explain with an example.
Answer
When non-metals react with oxygen, they form acidic oxides or neutral oxides.
Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide. Hydrogen reacts with oxygen.
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Question 172 Marks
What type of oxides are formed when metals combine with oxygen? Explain with the help of an example.
Answer
When metals combine with oxygen, they form basic oxides.
Example: Sodium reacts with oxygen to form a basic oxide called sodium oxide.
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Question 182 Marks
What is the nature of the oxide SO? What happens when it is dissolved in water ? Write the chemical equation of the reaction involved.
Answer
SO2 is acidic in nature. When dissolved in water, it produces sulphurous acid.
$\underset{\substack{\text { Sulphurdioxide } \\ \text { (Acidic oxide) }}}{SO_2(g) }+\underset {\text { Water}} {H_2O(I) } \rightarrow {}\underset{\substack{\text {  Sulphurcus acid } \\ \text { (Acid) }}}{ H_2SO_3 (aq)}$
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Question 192 Marks
What is the nature of the oxide Na2O? What happens when it is dissolved in water ? Write the chemical equation of the reaction inolved.
Answer
Na2O is basic in nature. When dissolved in water, it forms an alkali called sodium hydroxide.
$\underset{\substack{\text { Sodium Oxide} \\ \text { (Basic oxide)}}}{ Na_2 O(s) }+\underset {\text { Water}} {H_2O(I) } \rightarrow {}\underset{\substack{\text { Sodium hydroxide } \\ \text { (Alkali)}}}{ NaOH (aq)}$
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Question 202 Marks
What is meant by the reactivity series of metals? Arrange the following metals in an increasing order of their reactivities towards water:
Zinc, Iron, Magnesium, Sodium
Answer
The arrangement of metals in a vertical column in the order of decreasing reactivities is called reactivity series.
Increasing order of reactivity: Iron < zinc < magnesium < sodium
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Question 212 Marks
What is meant by the ‘concentration of ore’?
Answer
Before extracting metal from an ore, it is necessary to remove these impurities (gangue) from it. By removing the gangue, we get a concentrated ore containing a much higher percentage of metal. This is called concentration of ore; also known as enrichment of ore.
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Question 222 Marks
What is meant by saying that the metals are malleable and ductile? Explain with examples.
Answer
Metals are malleable i.e. they can be beaten into thin sheets with a hammer.
Example: Aluminium.
Metals are ductile i.e. they can be drawn into thin wires.
Example: Copper.
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Question 232 Marks
What is meant by ‘anodising’? Why is it done?
Answer
The process of thickening of aluminium oxide layer on the surface of aluminium objects by electrolysis is called anodizing. It is done to provide more protection to the aluminium object from corrosion.
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Question 242 Marks
What is meant by 22 carat gold? Name the metals which are usually alloyed with gold to make it harder.
Answer
It means that 22 parts pure gold is alloyed with 2 parts of either silver or copper for making ornaments; Silver and copper are usually alloyed with gold to make it harder.
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Question 252 Marks
What is an ionic bond? What type of bond is present in oxygen molecule?
Answer
The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond.
Covalent bond is present in an oxygen molecule.
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Question 262 Marks
What is an alloy? How is an alloy made?
Answer
An alloy is a homogeneous mixture of two or more metals (or a metal and small amount of non-metals). An alloy is prepared by mixing the various metals in molten state in required proportions, and then cooling their mixture to the room temperature.
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Question 272 Marks
What is an alloy? Give two examples of alloys.
Answer
An alloy is a homogeneous mixture of two or more metals (or a metal and small amounts of non-metals).
Steel and Brass are examples of alloys.
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Question 282 Marks
What is a covalent bond? What type of bond exists in (i) CCl4, and (ii) CaCl2?
Answer
The chemical bond formed by the sharing of electrons between two atoms is known as a covalent bond.
  1. Covalent bonds.
  2. Ionic bonds.
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Question 292 Marks
What happens when calcium reacts with water? Write the chemical equation of the reaction of calcium with water.
Answer
Calsium reacts with cold water to form calcium hydroxide and hydrogen gas.
$\text{Ca}\text{(s)}+2\text{H}_2\text{O(l)}\rightarrow\text{Ca(HO)}_2\text{(aq)}+\text{H}_2\text{(g)}$
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Question 302 Marks
What happens when calcium reacts with chlorine? Write an equation for the reaction which takes place.
Answer
Calcium reacts vigorously with chlorine to form an ionic chloride called calcium chloride.
$\text{Ca(s)}\ \ \ \ \ \ +\ \ \ \ \ \ \text{Cl}_2(\text{g})\xrightarrow{\ \ \ \ \ \ \ \ \ \ \ \ \ \ }\text{CaCl}_2(\text{s})\\\text{Calciam}\ \ \ \ \ \ \ \ \ \text{Cholorine}\ \ \ \ \ \ \ \ \ \text{Calcium chloride}$
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Question 312 Marks
What happens when a rod of zinc metal is dipped into a solution of copper sulphate? Give chemical equation of the reaction involved.
Answer
When a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper sulphate solution fades gradually and red brown coating of copper is deposited on the zinc strip.
$\underset{\text { Zinc }}{ Zn ( s )}+\underset{\text { Copper sulphate }}{ CuSO _4( aq )} \longrightarrow \underset{\text { Zinc sulphate }}{ ZnSO _4( aq )}+\underset{\text { Copper }}{ Cu ( s )}$
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Question 322 Marks
The electronic configurations of two elements A and B are given below:
A 2, 6
B 2, 8, 1
What type of chemical bond is formed between the two atoms of A?
What type of chemical bond will be formed between the atoms of A and B?
Answer
  1. Covalent bond.
  2. Ionic bond.
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Question 332 Marks
The atomic number of an element Y is 16.
  1. What must an atom of Y do to achieve the nearest inert gas electron arrangement?
  2. Which inert gas is nearest to Y?
Answer
  1. A n atom of Y a ccepts 2 electrons to achieve the nearest inert gas electron arrangement (2, 8, 8).
  2. Argon.
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Question 342 Marks
The atomic number of an element X is 12.
  1. What must an atom of X do to attain the nearest inert gas electron configuration?
  2. Which inert gas is nearest to X?
Answer
  1. An atom of X loses 2 electrons to attain the nearest gas electron configuration (2, 8).
  2. Neon.
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Question 352 Marks
$\text{CuSO}_4\text{(aq)}+\text{Fe(s)}\xrightarrow{\ \ \ \ }\text{FeSO}_4\text{(aq)}+\text{Cu(s)}$
$\text{FeSO}_4\text{(aq)}+\text{Zn(s)}\xrightarrow{\ \ \ \ \ }\text{ZnSO}_4\text{(aq)}+\text{Fe(s)}$
On the basis of the above reactions, indicate which is most reactive and which is least reactive metal out of zinc, copper and iron.
Answer
In the first reaction, Fe displaces Cu from CuSO4 solution. So Fe is more reactive than Cu.
In the second reaction, Zn displaces Fe from FeSO4 solution. So Zn is more reactive than Fe.
Hence it can be concluded that Zn is the most reactive metal and Cu is the least reactive metal out of zinc, copper and iron.
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Question 362 Marks
Silver metal does not combine easily with oxygen but silver jewellery tarnishes after some time. How?
Answer
The silver articles combine slowly with the hydrogen sulphide gas present in air to form a black coating of silver sulphide. The tarnishing of the silver objects is due to this silver sulphide coating on the object’s surface.
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Question 402 Marks
  1. Copper.
  2. Zinc.
  3. Nickel.
  4. Gold.
  5. Silver.
Answer
Anode – Thick block of i mpure metal M.
Cathode – Thin strip of p ure metal M.
Electrolyte – Water soluble salt (of metal M).
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Question 412 Marks
Non-metals react with oxygen to form acidic oxides or neutral oxides. Carbon burns in air to form carbon dioxide.
$\text{C(s)}+\text{O}_2\text{(g)}\rightarrow\text{CO}_2\text{(g)}$
The nature of the product formed is acidic. When carbon dioxide dissolves in water, it forms carbonic acid. It turns blue litmus to red which shows it is acidic in nature.
Answer
Carbon (Diamond).
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Question 422 Marks
Name two ores of zinc. Write the names of the chemical compounds present in them and give their chemical formulae.
Answer
  1. Calamine; Zinc carbonate, ZnCO3.
  2. Zinc blende; Zinc sulphide, ZnS.
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Question 432 Marks
Name one ionic compound containing chlorine and one covalent compound containing chlorine.
Answer
Ionic co mpound: Sodium chloride, NaCl.
Cova lent c ompound: Carbon tetrachloride, CCl4.
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Question 442 Marks
Metals X and Y can be recovered from the anode mud left behind after the electrolytic refining of copper metal. The coins made of metal X look new even after several years of use but the coins made of metal Y lose their shine gradually and get blackened soon. When metal X is alloyed with a small amount of metal Y, it becomes hard and hence suitable for making ornaments. What are metals X and Y ? Also state the colour of metal X.
Answer
Metal X is gold and Metal Y is silver; The colour of metal X (gold) is yellow.
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Question 452 Marks
In the formation of a compound XY atom X gives one electron to each Y atom. What is the nature of bond in XY2? Give two properties of XY2.
Answer
XY2 has ionic bonds.
  1. XY2 would conduct electricity when dissolved in water.
  2. XY2 would have high melting and boiling point.
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Question 462 Marks
In nature, metal A is found in a free state while metal B is found in the form of its compounds. Which of these two will be nearer to the top of the activity series of metals?
Answer
The metal B will be nearer to the top of the activity series of metals because this metal is so reactive that it reacts with most elements to form its compounds. But metal A is less reactive as it exists in free state without reacting with other elements.
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Question 472 Marks
In a solution of lead acetate, a strip of metal M was dipped. After some time, lead from the solution was deposited on the metal strip. Which metal is more reactive, M or lead?
Answer
The metal M is more reactive than lead because M displaces lead from lead acetate solution, which can be done only by an element that is more reactive lead.
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Question 482 Marks
In an electrolytic tank, aluminium metal is being extracted by the electrolysis of molten aluminium oxide using carbon electrodes. It is observed that one of the carbon electrodes is gradually burnt away and has to be replaced.
  1. Which carbon electrode (cathode or anode) is burnt away?
  2. Why is this carbon electrode burnt away?
Answer
  1. Positively charged carbon electrode (Anode).
  2. This carbon electrode is burnt away because oxygen produced during the electrolysis of molten aluminium oxide reacts gradually with the carbon of carbon anode to form carbon dioxide gas.
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Question 492 Marks
Hydrogen is not a metal but still it has been assigned a place in the reactivity series of metals. Why?
Answer
Though hydrogen is not a metal but it has been placed in the reactivity series of metals due to the fact that like metals, hydrogen also loses electrons and forms positive ions.
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Question 502 Marks
How is sodium metal extracted? Explain with the help of equation of the reaction involved.
Answer
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.
$2\text{NaCl(l)}\xrightarrow{\text{Electrolysis}}2\text{Na(s)}+\text{Cl}_2\text{(g)}$
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