1) Which of the following pairs will give displacement
reactions?
reactions?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
ANSWER:-AgNO3 solution and copper metal will give displacement
reaction.
reaction.
2) Which of the following methods is suitable for preventing an
iron frying pan from rusting?
iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) all of the above.
ANSWER:-Applying a coating of zinc.
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
melting point. This compound is also soluble in water. The element is likely to be
(a) Calcium
(b) Carbon
(c) Silicon
(d) Iron
ANSWER:- Calcium.
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.
ANSWER:- Food cans are coated with tin and not with zinc because
zinc is more reactive than tin.
zinc is more reactive than tin.
5) You are given a hammer, a battery, a bulb, wiresand a switch.
(a) How could you use them to distinguish between samples of
metals and non-metals?
metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing
between metals and nonmetals.
between metals and nonmetals.
ANSWER:-a)We can beat the sample with hammer and if it can be
beaten into thin sheets then its a metal otherwise a nonmetal. Similarly, the
battery,bulb, wires, and a switch arrange to set up a circuit with the sample.
If the sample conducts electricity, then it is a metal otherwise a non-metal.
beaten into thin sheets then its a metal otherwise a nonmetal. Similarly, the
battery,bulb, wires, and a switch arrange to set up a circuit with the sample.
If the sample conducts electricity, then it is a metal otherwise a non-metal.
b) It is useful in distinguishing between metal and non metals.
6)What are amphoteric oxides? Give two examples of amphoteric
oxides.
oxides.
ANSWER:-Oxides of metals which have both acidic as well as basic
behaviour are known as amphoteric oxides.
behaviour are known as amphoteric oxides.
Examples:- aluminum oxide (Al2O3), zinc oxide (ZnO)
7) Name two metals which will displace hydrogen from dilute
acids, and two metals which will not.
acids, and two metals which will not.
ANSWER:-Sodium and Potassium will displace hydrogen from dilute acids as they more reactive than hydrogen. Metals that are less reactive than hydrogen do not
displace it for example: copper and silver.
displace it for example: copper and silver.
8) In the electrolytic refining of a metal M, what would you
take as the anode, the cathode and the electrolyte?
take as the anode, the cathode and the electrolyte?
ANSWER:-In the electrolytic refining of a metal M:
Anode → impure metal M
Cathode → thin strip of pure metal M
Electrolyte → Solution of salt of the metal M
9 ) Pratyush took sulphur powder on a spatula and heated it. He collected the gas
evolved by inverting a test tube over it, as shown in figure below. (Refer to the book)
evolved by inverting a test tube over it, as shown in figure below. (Refer to the book)
(a) What will be the action of gas
on
on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking
place.
place.
ANSWER:- (i) There will be no action on dry litmus paper.
(ii) The colour of litmus paper will turn red because sulphur is a non-metal and
the oxides of non-metal are acidic in nature.
the oxides of non-metal are acidic in nature.
(b) S+O2—>SO2
10) State two ways to prevent the rusting of iron.
ANSWER:-Two ways to prevent the rusting of iron are:
a) Galvanisation: An
iron article is coated with a layer of zinc metal, which prevents the iron to come
in contact with oxygen and moisture. Hence, rusting is prevented.
iron article is coated with a layer of zinc metal, which prevents the iron to come
in contact with oxygen and moisture. Hence, rusting is prevented.
b) By making alloys
11) What type of oxides is formed when non-metals combine with
oxygen?
oxygen?
ANSWER: – when non metals combine with oxygen it forms acidic
oxides.
oxides.
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, yet it is used to make
utensils for cooking.
utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into
oxides during the process of extraction.
oxides during the process of extraction.
ANSWER:- a)Platinum, gold and silver are used to make
jewellery because these are low reactive metal and do not corrode
easily and hence do not lose their shine
and lustre.
easily and hence do not lose their shine
and lustre.
c) The reaction of
these substances with oxygen is highly exothermic which may cause fire, also
they react with water to form base so they are kept in oil.
these substances with oxygen is highly exothermic which may cause fire, also
they react with water to form base so they are kept in oil.
d) This is because
aluminium is good conductor of heat and electricity. To prevent its reaction with
food at high temperature a protective layer of aluminium oxide is formed which
prevent further corrosion.
aluminium is good conductor of heat and electricity. To prevent its reaction with
food at high temperature a protective layer of aluminium oxide is formed which
prevent further corrosion.
e) Carbonate and
sulphide ores are usually converted into oxides during the process of
extraction because metals can be easily extracted from their oxides rather than
from their carbonates and sulphides.
sulphide ores are usually converted into oxides during the process of
extraction because metals can be easily extracted from their oxides rather than
from their carbonates and sulphides.
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.
with lemon or tamarind juice. Explain why these sour substances are effective
in cleaning the vessels.
ANSWER:-The citric acid present in the lemon or tamarind neutralises the basis copper
carbonate and dissolves the layer formed due to corrosion and gives the surface
of the copper vessel its characteristic lustre.
carbonate and dissolves the layer formed due to corrosion and gives the surface
of the copper vessel its characteristic lustre.
14) Differentiate between metal and non-metal on the basis of
their chemical properties.
their chemical properties.
ANSWER:-
|
Metals.
|
Non
Metals |
|
Oxides of metals are basic in nature.
|
Oxides of nonmetals
are acidic in nature
|
|
Metals are electropositive.
|
Non metals are electronegative
|
|
They act as reducing agents.
|
They act as oxidising agents
|
|
Metals form chlorides which are
electrovalent or ionic compounds. |
Non metals form chlorides which
are covalent compounds
|
15) A man went door to door posing as a goldsmith.
He promised to bring back the glitter of old and dull gold
ornaments. An unsuspecting lady 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?
ornaments. An unsuspecting lady 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?
ANSWER:-The solution he had used was Aqua regia which is a 3:1
mixture of conc. HCl and conc. HNO3.Aqua regia is a fuming, highly corrosive
liquid. It dissolves gold in it. Since the outer layer of the gold bangles is
dissolved in aqua regia so their weight was reduced drastically.
mixture of conc. HCl and conc. HNO3.Aqua regia is a fuming, highly corrosive
liquid. It dissolves gold in it. Since the outer layer of the gold bangles is
dissolved in aqua regia so their weight was reduced drastically.
16) Give reasons why copper is used to make hot water tanks and
not steel (an alloy of iron).
not steel (an alloy of iron).
ANSWER:-Copper does not react with cold water, hot water or steam.
However, iron reacts with steam. If the hot water tanks are made of steel. So,
copper is used to make hot water tanks.
However, iron reacts with steam. If the hot water tanks are made of steel. So,
copper is used to make hot water tanks.
3Fe+4H2O—>Fe3O4+4H2