Previous Year Paper year:2018 : ICSE-X-Chemistry

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ICSE-X-Chemistry

Previous Year Paper year:2018

with Solutions - page 3

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#1-f [5]
Give a reason for each of the following:

#1-f-i
Ionic compounds have a high melting point.
Ans : Ionic compounds have a high melting point, because the ionic bond in
these compounds is very strong and a lot of energy is required to break
the bond.

#1-f-ii
Inert gases do not form ions.
Ans : To attain stability, atoms need to complete their octet by sharing, losing
or gaining electrons. In inert gases, the octet is completed and they do
not need to gain, lose or share electrons; hence, they do not form ions.

#1-f-iii
Ionisation potential increases across a period, from left to right.
Ans : Ionisation potential increases across a period from left to right because
the atomic size decreases due to an increase in the nuclear charge. The
electrons in the outermost shell lie close to the nucleus and this makes
the removal of electrons difficult and requires more energy.

#1-f-iv
Alkali metals are good reducing agents.
Ans : Reducing agents are elements or groups of elements which easily lose
their electrons. Alkali metals are good reducing agents because they
have only one extra electron in their outermost shell; hence, to attain
stability, they easily lose the electron.

#1-f-v
Conductivity of dilute hydrochloric acid is greater than that of acetic acid.
Ans : Conductivity of dilute hydrochloric acid is greater than that of acetic acid.
This happens because hydrochloric acid is a strong acid. It ionises
completely and forms more ions than weak acetic acid.

#1-g [5]
Name the gas that is produced in each of the fallowing cases:

#1-g-i
Sulphur is oxidized by concentrated nitric acid.
Ans : Nitrogen dioxide (``\ce{NO2}``)

#1-g-ii
Action of dilute hydrochloric acid on sodium sulphide.
Ans : Hydrogen sulphide (``\ce{H2S}``)

#1-g-iii
Action of cold and & dilute nitric acid on copper.
Ans : Nitric oxide (``\ce{NO}``)

#1-g-iv
At the anode during the electrolysis of acidified water.
Ans : Oxygen (``\ce{O2}``)

#1-g-v
Reaction of ethanol and sodium.
Ans : Hydrogen (``\ce{H2}``)

#1-h [5]
Fill up the blanks with the correct choice given in brackets.

#1-i
Ionic or electrovalent compounds do not conduct electricity in their
________ state (fused/ solid)
Ans : Ionic or electrovalent compounds do not conduct electricity in their solid
state.

#1-i-iii
Electrolysis of aqueous sodium chloride solution will form ________ at
the cathode. (hydrogen gas / sodium metal)
Ans : Electrolysis of aqueous sodium chloride solution will form Sodium metal
at the cathode.