Previous Year Paper year:2012 : ICSE-X-Chemistry

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ICSE-X-Chemistry

Previous Year Paper year:2012

with Solutions - page 3

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#1-f-ii
ii. Ethanal

#1-f-iii
iii. Ethyne

#1-f-iv
iv. Acetone

#1-f-v
v. 2-methyl propane

#1-g
Concentrated nitric acid oxidises phosphorus to phosphoric acid according to the
following equation:
$$\ce{P + 5HNO3 (conc.) ->H3PO4 + H2O + 5NO2 }$$
If ``\pu{9.3 g }`` of phosphorus was used in the reaction, then calculate:
Ans :

#1-g-i [1]
i. Number of moles of phosphorus taken.

#1-g-ii [2]
ii. The mass of phosphoric acid formed.

#1-g-iii [2]
iii. The volume of nitrogen dioxide produced at STP.
[H = 1, N = 14, P = 31, O = 16]

#1-h [5]
Give reasons for the following:

#1-h-i
i. Iron is rendered passive with fuming nitric acid.
Ans : Cone. ``\ce{HNO_3}`` being a strong oxidising agent oxidises iron, forming a layer that makes iron non reactive or passive.

#1-h-ii
ii. An aqueous solution of sodium chloride conducts electricity.
Ans : Aqueous solution of sodium chloride contains mobile ions like ``\ce{Na+, Cl-, H+, OH-, H3O+}`` etc. so they conduct electricity.

#1-h-iii
iii. Ionisation potential of the element increases across a period.
Ans : Atomic size decreases and nuclear charges increases as we move from left to right in a period so energy required to remove one electron from the valence shell increases from left to right thus ionisation potential increases.

#1-h-iv
iv. Alkali metals are good reducing agents.
Ans : Alkali metals readily lose electrons from their valence shell and get oxidised. So they behave as good reducing agents.

#1-h-v
v. Hydrogen chloride gas cannot be dried over quick lime.
Ans : Hydrogen chloride is acidic whereas quick lime is basic. So they will react with each other hence quick lime can not be used to dry hydrogen chloride.

# [40]
Section : II
Attempt any four questions from this section.