Chapter 3 Metals and Non-metals
.jpg "RBSE Solutions for Class10 Science Chapter 3 Metals and Non-metals")
If you are preparing
for RBSE class 10 board exams, then these solutions of intext and end exercise
questions will help you a lot.
|
Board |
RBSE |
|
Subject |
Science |
|
Chapter |
Metals and
Non-metals |
|
No. of Intext
questions |
15 |
|
No. of End exercise
questions |
16 |
|
Prescribed Book |
NCERT Science |
Answers of Questions on Page 40
Q.1 Give an example of
a metal which
(i) is
a liquid at room temperature;
(ii) can
be easily cut with a knife;
(iii) is
the best conductor of heat;
(iv) is
the poorest conductor of heat;
Ans.-(i) Mercury
(Hg)
(ii). Sodium(Na)
(iii). Silver(Ag)
(iv) Lead (Pb)
Q.2 Explain the meaning
of malleable and ductile.
Ans.
Malleable: Substances that can be beaten into thin sheets are called malleable.
Example- The most of the metals are malleable.
Ductile: Substances that can
be drawn into thin wires are called ductile.
Example- The most of the metals are ductile.
Answers of Questions on Page 46
Q.1 Why sodium is kept
immersed in kerosene oil?
Ans. Sodium is highly reactive metal and it combines
with moisture present in the air and catches fire if kept in open. Therefore,
to prevent accidental fires, it is kept immersed in kerosene oil.
Q.2 Write equations for
the reaction of
(i) iron with steam (ii) Calcium and
potassium with water.
Ans.
(i).3Fe + 4 H2O(g) → Fe3O4(s) + 4H2(g)
(ii). Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
(iii).
2K + 2H2O(l) →
2KOH(aq) + H2(g)
Q.3 Samples of four
metals A, B, C and D were taken and added to the following solution one by one.
The results obtained have been tabulated as follows:
|
Metal |
Iron (II) sulphate |
Copper (II) sulphate |
Zinc sulphate |
Silver nitrate |
|
A B C D |
No reaction Displacement No reaction No reaction |
Displacement No reaction No reaction |
No reaction No reaction No reaction |
Displacement No reaction |
Use the table above to answer the following questions about metals A, B, C and D:
(i) Which is the most reactive metal?
(ii) What would you observe when B is added to a solution of Copper (II) sulphate?
(iii) Arrange the metals A, B, C and D in decreasing order of reactivity.
Ans.
(i). The most reactive metal- B
(ii). When metal B is added to copper sulphate solution, it displaces copper form its solution.
(iii) B > A > C > D
Q.4 Which gas is
produced when dilute hydrochloric acid is added to a reactive metal? Write the
chemical equation when iron reacts with dilute H2SO4.
Ans. Hydrogen gas is produced when dilute
hydrochloric acid reacts with a reactive metal.
Fe
+ H2SO4 →
FeSO4 + H2↑
Q.5 What would you
observe when Zinc is added to a solution of Iron (II) sulphate. Write the
chemical reaction that takes place.
Ans. When Zinc is added to a solution of Iron
(II) sulphate, it will displace iron from its aqueous solution.
Zn(s) +
FeSO4(aq) → ZnSO4(aq) +Fe(s)
This is a displacement reaction.
Answers of Questions on Page 49
Q.1 (i) Write electron-dot structures for sodium, oxygen and
magnesium.
(ii) Show the formation of Na2O and MgO by the transfer of electrons
(iii) What are the ions present in these compounds?
Ans.
(i). Electron dot structures for sodium, oxygen
and Magnesium
(i).
Sodium (2,8,1) = `\dot{Na}`
(ii). Oxygen (2,8,6) = `: \ddot{O}:`
(iii). Magnesium (2,8,2)=`\ddot{Mg}`
(ii). Formation of
Na2O and MgO by the transfer of electrons
(iii). Na+ and O- ions in Na2O
and Mg2+ and O-
are present in these compounds.
Q.2 Why do ionic
compounds have high melting points?
Ans.Ionic compounds are formed by
opposite charged ions so these compounds have strong electrostatic forces of
attraction between the ions. Therefore, it requires a lot of energy to overcome
these forces. That is why ionic compounds have high melting points.
Answers of Questions on Page 53
Q.1 Define the terms:
(a) Mineral, (b)
ore and (c) gangue.
Ans.
(i) Mineral.-Most of the elements occur in nature as compounds
and they have fixed chemical composition , they are called
minerals.
(ii) Ore. The mineral from which a metal can be extracted profitably
and easily is called ore.
(iii) Gangue. The impurity of sand and rocky materials present in the
ore, is known as gangue.
Q.2 Name two metals
which are found in nature in the Free State.
Ans. Gold and Silver
Q.3 What chemical
process is used for obtaining a metal from its oxide?
Ans. Reduction process is used for obtaining a
metal from its oxide. In
this process, metal oxides are reduced by using suitable reducing agents
such as carbon or by highly reactive metals to displace the metals from their
oxides.
Answers of Questions on Page 55
Q.1 Metallic oxide of
Zinc, Magnesium and Copper were heated with the following metals. In which
cases will you find displacement reactions taking place?
|
Metal |
Zinc |
Magnesium |
Copper |
|
Zinc oxide Magnesium oxide Copper oxide |
|
|
|
Ans.
|
Metal |
Zinc |
Magnesium |
Copper |
|
Zinc oxide |
No reaction |
Displacement |
No reaction |
|
Magnesium oxide |
No reaction |
No reaction |
No reaction |
|
Copper oxide |
Displacement |
Displacement |
No reaction |
Q.2 Which metals do not
corrode easily?
Ans. Gold and platinum do not corrode easily.
Q.3 What are alloys?
Ans. Alloy. “An alloy is a homogenous solid
solution of one metal with one or more metals or non-metals, such as brass,
bronze etc.”.
Answers of Questions EXERCISES
Q.1 Which of the
following Pairs will give displacement reactions
(a) NaCl solution and copper metal
(b) MgCl2
solution and aluminum metal
(c) FeSO4
solution and silver metal
(d) AgNO3
solution and copper metal
Ans. (d) AgNO3
solution and copper metal
Q.2 Which of the
following methods is suitable for preventing an iron frying pan from rusting.
(a) applying grease
(b) applying paint
(c) applying a coating of zinc
(d) all of the above
Ans. (c) applying
a coating of zinc
Q.3 An element reacts
with oxygen to give a compound with a high melting point. This compound is also
soluble in water. The element is likely to be
(a) calcium
(b) carbon
(c) silicon
(d) iron
Ans. (c) calcium
Q.4 Food cans are
coated with tin and not with zinc because-
(a) zinc is costlier than tin
(b) zinc
has a higher melting point than tin
(c) zinc
is more reactive than tin
(d) zinc
is less reactive than tin
Ans. (c) zinc
is more reactive than tin
Q.5 You are given a
hammer, a battery, a bulb, wires and a switch.
(a) How would you use them to distinguish between
samples of metals and non-metals.
(b) Assess the usefulness of these tests in
distinguishing between metals and non-metals.
Ans.
(a) (i) Beat the sample with hammer, if
it does not break and change into sheet it is metal and if if breaks on
hammering it is non-metal.
(ii) we can use the battery, bulb,
wires, and a switch to set up a circuit with the sample. If the sample conducts
electricity, then it is a metal and if bulb does not glow then it is a non-metal.
(b). The
above tests are useful in distinguishing between metals and non-metals as these
are based on the physical properties. No chemical reactions are involved
in these tests.
Q.6 What are amphoteric
oxide? Give examples of two amphoteric oxides.
Ans. The oxides which show acidic and basic
both characters and react with bases and acids to form salt and water are
called amphoteric oxides. e.g.Aluminum oxide[Al2O3] and zinc
oxide[ZnO]
Eq. Al2O3 +
6HCl → 2AlCl3
+ 3H2O
Al2O3 +
2NaOH → 2AlNaO2+ H2O
Q.7 Name two metals
which displace hydrogen from dilute acids and two metals which will not.
Ans. Metals which displaces hydrogen from
dilute acids: Na & K
Metals which does not displaces
hydrogen from dilute acids: Cu & Ag
Q.8 In the electrolytic
refining of a metal M, what would you take as the anode, cathode and
electrolyte?
Ans. In the electrolyte refining of a metal M
–
Anode → impure metal M
Cathode → thin strip of pure metal M
Electrolyte → Solution of salt of the
metal M
Q.9 Pratyush took
sulphure powder on a spatula and heated it. He collected the gas evolved by
inverting a test tube over it as shown in Fig. below:
 |
| Collecting gas |
(a) What will be the action of gas on?
(i) Dry litmus paper?
(ii) Moist litmus paper?
(b) Write
a balanced chemical equation for the reaction taking place.
Ans.
(a) (i) There will be no action of gas on dry litmus
paper.
(ii) On moist litmus paper, the gas will change it to red.
(b) S(s) +
O2(g) → SO2
Q.10 State two ways
to prevent the rusting of iron.
Ans.(i) Oiling,
greasing, or painting: By applying oil, grease, or paint, the surface
becomes water proof and the moisture and oxygen present in the air cannot come
into direct contact with iron. So by this method rusting is prevented.
(ii) Galvanisation: An
iron article is coated with a layer of zinc metal, which prevents
the iron to come in contact with oxygen and moisture. By
this method rusting is prevented.
Q.11 What type of
oxides formed when non-metals combine with oxygen?
Ans. Acidic oxides are formed when non-metals
combine with oxygen.
S
+ O2 →
SO2
Q.12 Give reasons:
(a) Platinum,
gold and silver are used to make jewellery.
(b) Sodium,
potassium and lithium are stored under oil.
(c) Aluminum
is a highly reactive metal; still it is used to make utensils for cooking.
(d) Carbonate
and sulphide ores are usually converted into oxides during the process of
extraction.
Ans. (a) Platinum,
gold and silver do not react with atmospheric and other reagents and they are
very lustrous so they are used to make jewellery.
(b) Sodium, potassium and lithium are stored
under oil because they are highly reactive and combine with atmospheric oxygen
and catch fire when they are kept in open air.
(c) Aluminum is a reactive metal; but it is
used to make utensils used for cooking because aluminum reacts with oxygen of
atmosphere to form aluminum oxide(Al2O3) which is
non-reactive and makes a sticky layer over it which prevents further reaction.
(d) Carbonate and sulphide ores are usually
converted to oxides because metals can be easily
extracted from their oxides rather than from their carbonates and sulphides
Q.13 You must
have seen tarnished copper vessels being cleaned with lemon or tamarind juice.
Explain why these sour substances are effective in cleaning the vessels.
Ans. Copper reacts with moist carbon dioxide
in air to form copper carbonate and as a result, copper vessel loses its shiny
brown surface forming a green layer of copper carbonate. When these types of
vessels are cleaned with lemon or tamarind juice containing acids, shining
surface again visible.
Q.14 Differentiate
between metal and non-metal on the basic of their chemical properties.
Ans. Metal and non-metal show the following
differences in their chemical properties.
1.(a) Mostly the metals react with oxygen to form
basic oxides.
4Na
+ O2 → Na2O
2Mg
+ O2 → 2MgO
(b) Non-metals react with oxygen to form
acidic oxides.
S
+ O2 →
SO2
2.(a)
Most of the metals reacts with water to form oxides and hydroxides
2Na + 2H2O →
2NaOH + H2 ↑
(b) Non- metals do
not react with water
3. (a) Most of the metals react with dilute
acids to produce salt and hydrogen gas is evolved
2Na +
2HCl → 2NaCl
+ H2 ↑
(b) Non metals do not react with acids.
Q.15 A man went
door to door posing to be a goldsmith. He promised to give back the glitter to
old and dull gold ornaments. An unsuspecting housewife gave a set of gold
bangles to him which he dipped in a particular solution. The bangles sparkled
like new but their weight was reduced drastically. The lady was upset but after
a futile argument the man beat a hasty retreat. Can you play the detective to
find out the nature of the solution he had used?
Ans. The man must have dipped the gold bangles
which is a mixture of conc. HCl and conc. HNO3in ration 3: 1 . This
mixture is known as ‘ Aqua Regia’ or ‘ Royal water’ which dissolves gold that’s
why the bangles sparkled like new due to dissolving of gold, their weight was
reduced.
Q.16 Give the
reason why copper is used to make hot water tanks but steel (an alloy of iron)
is not.
Ans. Copper does not react with cold
water, hot water, or steam, so it is used to make water tanks but steel an
alloy of iron is not used because iron reacts with hot water.
3 Fe
+ 4H2O → Fe3O4 + 4H2
That is why copper is used to make hot water tanks,
and not steel.
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