Tag: hydrogen and its compounds

Questions Related to hydrogen and its compounds

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 $374.4 K$.

Which compound is formed when calcium carbide reacts with heavy water?

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

  1. $C _{2}D _{2}$

  2. $CaD _{2}$

  3. $CD _{2}$

  4. $Ca _{2}d _{2}$

Show answer
Correct Option: A
Explanation:
When calcium carbide reacts with heavy water, deuterated acetylene ($C _{2}D _{2}$) is formed.
$CaC _{2} + 2D _{2}O \rightarrow C _{2}D _{2} + Ca(OD) _{2}$

If a mole of hydrogen molecule is heated to a high temoerature then which of the following reactions take place?

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

  1. $H _2{(g)} + 436 kJ mol^{-1} \rightarrow H{(g)} + H{(g)}$

  2. $2H2{(g)} + 820 kJ mol^{-1} \rightarrow 2H _2{(g)}$

  3. $H _2{(g)} + H _2{(g)} + 436kJ mol^{-1} \rightarrow H^{+} _{(aq)} + H^{-} _{(aq)}$

  4. $H _2{(g)} + 200kJ mol^{-1} \rightarrow H _{(g)} + H _{(g)}$

Show answer
Correct Option: A
Explanation:

The amount of energy required to break $H-H$ bond of 1 mole of gaseous hydrogen is 436 $kJ \ mol^{-1}$. This is known as bond dissociation enthalpy.
$H _2{(g)} + 436 \  kJ mol^{-1} \rightarrow  H{(g)} + H{(g)}$

Some of the major uses of heavy water are given below. Which one is not correct?

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

  1. It is used as a moderator in nuclear.

  2. It is used as a tracer compound for studying reaction mechanism

  3. High concentration of heavy water accelerates the growth of plants

  4. It is used in preparing deuterium

Show answer
Correct Option: C
Explanation:

High concentration of heavy water retards the growth of the plants. Tobacco seeds do not grow in heavy water.