Question 1
Which of the following pairs will give displacement 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
Option d) AgNO
3 solution and copper is correct answer. Copper
displace the silver
Cu(s) + 2AgNO3 (aq) → Cu(NO3)2 (aq) + 2Ag (s)
Question 2
Which of the following methods is suitable for preventing an iron
frying pan from rusting?
Applying grease
Applying paint
Applying a coating of zinc
All of the above
Answer
(c) Applying a coat of Zinc
Question 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
Answer
option (a) i.e Calcium.
Question 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
c) Zinc is more reactive than tin
Question 5
You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could 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.
Answer
a) Metals show malleable property we can be easily drown into sheets by hitting with hammer. On the other
hand non-metals they are non-malleable if we beat with hammer they break sample
b) Metals are good conductors of electricity when we connect it into circuit using battary , switch wire
and bulb the bulb start glows.then the sample are metal Similarly non-metals are bad conductors of
electricity if the bulb not glows means samples are non metal
Question 6
What are amphoteric oxides? Give two examples of amphoteric oxides
Answer
The Oxides which react with both acids and bases to produce salt and water
are known as amphoteric oxides.
Al
2O
3 + 6HCl → 2AlCl
3 + 3H
2O
Al
2O
3 + 2NaOH → 2NaAlO
2+ H
2O
ZnO + 2HCl → ZnCl
2 + H
2O
ZnO + 2NaOH → Na
2ZnO
2 + H
2O
Question 7
Name two metals which will displace hydrogen from dilute acids, and
two metals which will not.
Answer
The two metals which will displace Hydrogen from dilute acids are Zinc and
Magnesium because they are very reactive metals. And copper, silver are the metals which will not replace
Hydrogen from dilute acids because these metals are less reactive.
Question 8
In the electrolytic refining of a metal M, what would you take as
the anode, the cathode and the electrolyte?
Answer
We take
Pure metal M at Cathode
Impure metal M at Anode
A water soluble salt of metal M at Electrolyte
Question 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 the figure.
(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.
Solution: a) When sulphur powder is heat in the air sulphur dioxide is formed.
(i) Sulphur dioxide does not show action on dry litmus paper.
(ii) Sulphur dioxide turn the moist litmus paper from blue to red
(b) S(s) + O2(g) → SO2(g)
Question 10
State two ways to prevent the rusting of iron.
Answer
Two ways to prevent the rusting of iron are following
galvanisation
Greasing
Question 11
What type of oxides are formed when non-metals combine with oxygen?
Answer
When non-metals combine with oxygen it forms acidic or neutral
oxides.Suphur form an acidic oxide ,Hydrogen form an neutral oxide.
Question 12
Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction
Answer
(a) Platinum, gold and silver are used to make jewellery because they are very less reactive , luster
malleable and ductile in nature and also show high corrosion .
(b) Sodium, potassium and lithium are stored under oil to prevent their reaction with air as they are
very reactive and catch fire when exposed to air.
(c) Aluminium forms a non-reactive layer of aluminium oxide all over its surface in presence of air .
This layer prevents aluminium to react with other substances. That’s why aluminium is used to make
cooking utensils.
(d) It is easy to extract metal form its oxide rather than from their carbonates or sulphides.
Question 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.
Answer
Copper reacts with air to form copper carbonate.Lemon or tamarind juice contain acids Lemons juice
contain citric acid and termarind contains tartaric acids these acids dissolve the coating of copper
oxide or basic copper carbonate present on the surface of tarnished copper vessels and make them
shining red brown again
Question 14
Differentiate between metal and non-metal on the basis of their
chemical properties.
Answer
| Metals |
Non-metals |
| Metals replace hydrogen from acids and form salts.
|
Non-metals do not replace hydrogen from acids |
| Metals form basic oxides or amphoteric oxides.
|
Non-metals form acidic or neutral oxides.
|
| Metals are lustrous. |
Non-metals are non-lustrous |
| Metal turn red litmus paper to blue |
Non metal turn blue litmus paper to red |
| Metals are the good conductors of electricity and heat. |
Non-metals are non-conductors of electricity and heat except graphite is the
exception |
| All metals are solids except mercury. |
Non-metals are in solid-liquid and gaseous |
Question 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?
Answer
Goldsmith dipped the gold ornaments in Aqua regia solution. It is the
mixture of concentrated Hydrochloric acid and concentrated nitric acid. Aqua-regia dissolved a
considerable amount of gold from gold bangles and reduced their weight drastically.
Question 16
Give reasons why copper is used to make hot water tanks and not
steel (an alloy of iron).
Answer
Copper is used to make hot water tanks and not steel because copper does
not reacts with water or steam whereas iron reacts with steams to corrode the tank.