Tag: chemistry

Questions Related to chemistry

The high boiling point of water is due to:

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. its high specific heat

  2. hydrogen bonding

  3. high dielectric constant

  4. low dissociation constant

Show answer
Correct Option: B
Explanation:

Higher boiling point of water is due to hydrogen bonding. Several water molecules associate through H-bonding. Large amount of energy is required to break this association.

Which of the following is not true?

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. Hardness of water depends on its behaviour towards soap

  2. The temporary hardness is due to the presence of Ca and Mg bicarbonates

  3. Permanent hardness is due to the presence of soluble Ca and Mg sulphates

  4. Permanent hardness can be removed by boiling the water

Show answer
Correct Option: D
Explanation:

Permanent hardness is the hardness that cannot be removed by boiling. It is usually caused by the presence of calcium sulphate or magnesium sulphates or chlorides, nitrates of Ca, Mg in the water which does not precipitate out as the temperature increases.


Hence, option D is correct.

The boiling point of $D _{2}O$ is greater than $H _{2}O$. It is because:

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. $D _{2}O$ has lower $K _w $ value

  2. $D _{2}O$ has a lower dielectric constant

  3. $D _{2}O$ is a associated liquid

  4. the molecular weight of $D _{2}O$ is greater than $H _{2}O$

Show answer
Correct Option: D
Explanation:

$D _2O$ has a somewhat higher boiling point because its molecular weight is about $(16+2+2=20)$ and $H _2O$ is about $(16+1+1=18)$.

Which of the following compounds take part in exchange reaction with $D _{2}O$?

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. $NaOH$

  2. $H _{3}PO _{2}$

  3. $H _{3}PO _{3}$

  4. All the above

Show answer
Correct Option: D
Explanation:

${ D } _{ 2 }O$ can exchange proton from $-OH$ group of given options.

Compare the bond energy (B.E) of $O-H$ in water and $O-D$ in heavy water:

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. B.E of $O-H >$ B.E of $O-D$

  2. B.E of $O-H <$ B.E of $O-D$

  3. B.E of $O-H =$ B.E of $O-D$

  4. B.E of $O-H =$ 2 times B.E of $O-D$

Show answer
Correct Option: B
Explanation:

Boiling point of heavy water is more than normal water and therefore, bond energy of $O-H$ bond in water is lesser than bond energy of $O-D$ bond in heavy water. 


Also, bond length of $O-H$ is greater than $O-D$ and bond energy is inversely proportional to bond energy.

Heavy water is obtained by ?

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. boiling water

  2. heatiing $H _{2}O _{2}$

  3. Prolonged electrolysis of $H _{2}O$

  4. All of these

Show answer
Correct Option: C
Explanation:

$D _{2}O$ is prepared by repeated electrolysis of ordinary water which contains a small amount of alkali. Ordinary water contains a very very small fraction (about 1 part in 6000 parts) of heavy water.

The boiling point of heavy water is?

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. $100^{0}C $

  2. $101.4^{0}C $

  3. $99^{0}C $

  4. $110^{0}C $

Show answer
Correct Option: B
Explanation:

The boiling point of heavy water is $101.4^{0}C $ or $374.4 K$. Its melting point is $3.8^{0}C $ or $276.8 K$.

Atomic nuclear reactors use heavy water. This is different from ordinary water only to the extent that in place of hydrogen it contains:

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. deuterium, a heavier isotope of hydrogen

  2. nitrogen, which is also a light element

  3. tritium, an heavier isotope of hydrogen

  4. a radioactive element

Show answer
Correct Option: A
Explanation:

Heavy water $(D _2O)$ is a compound containing deuterium and oxygen. It is used in the atomic nuclear reactor as a moderator. It differs from ordinary water $(H _2O)$ only because it has Deuterium i.e. a heavy isotope of hydrogen.

Heavy water is used as:

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. drinking water

  2. detergent

  3. washing water

  4. a moderator

Show answer
Correct Option: D
Explanation:

In nuclear reactors, heavy water is used as moderator for neutrons.

Heavy water $(D _{2}O)$ freezes at ?

chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

  1. $-3.8^{0}C$

  2. $3.8^{0}C$

  3. $0^{0}C$

  4. $38^{0}C$

Show answer
Correct Option: B
Explanation:
The freezing point of heavy water is $3.8^{0}C $ or $276.8 K$. The boiling point is $101.4^{0}C $ or $374.4 K$.