ANSWER ALL THESE....
ONE MARK QUESTIONS
1. In electrolysis of water, why is the volume of gas
collected over one electrode double that of gas
collected over the other electrode.
Ans : [CBSE S.R 2018, CBSE 2009, 2012, 2013]
Water contains hydrogen and oxygen in the ratio of
2 : 1, that is why volume of H2
is double than that of
oxygen.
2. What can be seen when a strip of copper metal is
placed in a solution of silver nitrate?
Ans : [CBSE 2015]
The solution will become blue, shiny silver metal will
get deposited.
Cu(s) + 2AgNO3
(aq) $ Cu(NO3
)2 (aq) + 2Ag(s)
3. State one industrial application of reduction process.
Ans : [CBSE 2015]
It is used in the extraction of metals e.g.,
ZnO(s) + C(s) Heat Zn(s) + CO2
(g)
4. Which one of the following is a chemical change? Give
reason also.
(a) Burning of wax (b) Melting of wax
Ans : [CBSE 2014]
Burning of gas is a chemical change because new
products with new properties will be formed on
burning.
5. Which one is a chemical change:
Rusting of iron or melting of iron?
Ans : [CBSE 2014]
Rusting of iron is a chemical change.
6. State one basic difference between a physical change
and a chemical change.
Ans : [CBSE 2014, 2011]
In a physical change, no new substance is formed.
In a chemical change, new substance(s) with new
properties is/are formed.
7. Name the oxidising and reducing agent in the following
reaction:
CuO + H2 $ Cu + H2
O
Ans : [CBSE 2013]
CuO is oxidising agent H2
is reducing agent.
8. Write a complete balanced chemical equation for the
following reaction:
Sodium hydroxide + Sulphuric acid $ Ans : [CBSE 2013]
2NaOH + H2
SO4
$ Na2
SO4
+ 2H2
O
9. Name and state the law which is kept in mind when
we balance chemical equations.
Ans : [CBSE 2012]
Law of conservation of mass. It states Matter can
neither be created nor be destroyed. The total mass
of reactants must be equal to total mass of products.
10. What is meant by a chemical reaction?
Ans : [CBSE 2011]
Chemical reaction, a process in which one or more
substances, the reactants, are converted to one or more
different substances, the products. Substances are
either chemical elements or compounds. A chemical
reaction rearranges the constituent atoms of the
reactants to create different substances as products
11. AgNO3
(aq) + NaCl(aq) $ AgCl . + NaNO3
(aq)
FeS + H2
SO4 $ FeSO4
+ H2
S -
Consider the above mentioned two chemical equations
with two different kinds of arrows (- and . ) along
with the product. What do these two different arrows
indicate?
Ans : [CBSE 2011]
- shows evolution of gas, . represents a precipitate.
12. Hydrogen being a highly inflammable gas and
oxygen being a supporter of combustion, yet water, a
compound made up of hydrogen and oxygen is used to
extinguish fire. Why?
Ans : [CBSE 2011]
H2
O is a compound constituted of hydrogen of oxygen
elements and being a compound it has different
properties as compared to its constituting elements.
13. N2
(g) + 3H2
(g) $ 2NH3
(g), name the type of
reaction.
Ans : [CBSE 2011]
Combination reaction.
14. If copper metal is heated over a flame it develops
a coating. What is the colour and composition of
coating?
Ans : [CBSE 2011]
Black coloured coating is formed. It is a due to
formation of copper oxide.
Answers
12. Hydrogen being a highly inflammable gas and
oxygen being a supporter of combustion, yet water, a
compound made up of hydrogen and oxygen is used to
extinguish fire. Why?
Ans :- oxygen being a supporter of combustion, yet water, a compound made up of hydrogen and oxygen is used to extinguish fire because the chemical formula of hydrogen is h or h2 and the combustion is the process in which the fossil fuel are substance burn in the presence of oxygen water is the best fire extinguisher for the fire but some places water are not suitable for extinguishing fire like electricity transformer for petrol pump. but water ( H2O ) is act like a fire extinguisher. the best source of fire extinguisher is carbon dioxide ( CO2 ) gas because carbon dioxide ( CO2 ) gas is more comfortable then water ( H2O ) that's why Hydrogen being a highly inflammable gas and oxygen being a supporter of combustion, yet water, a compound made up of hydrogen and oxygen is used to extinguish fire.
Answer:
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