Hydrogen Questions and Answers Part-2

1. The alum used for purifying water is
a) Ferric alum
b) Chrome alum
c) Potash alum
d) Ammonium alum

Answer: c
Explanation: Potash alum is used for purifying water.

2. The boiling point of water is exceptionally high because
a) there is covalent bond between H and O
b) water molecule is linear
c) water molecules associate due to hydrogen bonding
d) water molecule is not linear

Answer: c
Explanation: The high boiling point of water is due to H-bonding

3. The H–O–H angle in water molecule is about
a) 90º
b) 180º
c) 102º
d) 105º

Answer: d
Explanation: The hybridisation in water is sp3 and bond angle 105º

4. When two ice cubes are pressed over each other, they unite to form one cube. Which of the following forces is responsible to hold them together ?
a) Hydrogen bond formation
b) van der Waals forces
c) Covalent attraction
d) Ionic interaction

Answer: a
Explanation: Two ice cubes stick to each other due to H-bonding

5. The process used for the removal of hardness of water is
a) Calgon
b) Baeyer
c) Serpeck
d) Hoope

Answer: a
Explanation: Calgon process is used to remove permanent hardness of water

6. Pure water can be obtained from sea water by
a) centrifugation
b) plasmolysis
c) reverse osmosis
d) sedimentation

Answer: c
Explanation: Sea water is purified by reverse osmosis

7. Polyphosphates are used as water softening agents because they
a) form soluble complexes with anionic species
b) precipitate anionic species
c) form soluble complexes with cationic species
d) precipitate cationic species

Answer: c
Explanation: Polyphosphates form soluble complexes with Ca2+ and Mg2+ and are removed.

8. What is heavy water ?
a) \[H_{2}O^{18}\]
b) \[H_{2}O^{16}\]
c) \[H_{2}O_{3}\]
d) \[D_{2}O\]

Answer: d
Explanation: D2O is heavy water

9. \[D_{2}O\]  is used in
a) industry
b) nuclear reactor
c) medicine
d) insecticide

Answer: b
Explanation: D2O is used in nuclear reactors as moderators.

10. What is formed when calcium carbide reacts with heavy water?
a) \[C_{2}D_{2}\]
b) \[CaD_{2}\]
c) \[Ca_{2}D_{2}O\]
d) \[CD_{2}\]

Answer: a
Explanation: CaC2 + 2D2O \[\rightarrow\]   C2D2 + Ca(OD)2