Tag: chemistry

Questions Related to chemistry

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.

What is heavy water?

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

  1. $H _{2}O^{18}$

  2. $D _{2}O$

  3. $H _{2}O^{17}$

  4. $H_{2}O

Show answer
Correct Option: B
Explanation:

Deuterium oxide $D _{2}O$ is known as heavy water. When both $H$ atoms of water $(H _2O)$ are replaced with $D$ atoms, heavy water is obtained.

Calcium carbide + heavy water $\rightarrow$ ?
The product of the above reaction is:

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

  1. $C _2H _2$

  2. $CaD _2$

  3. $Ca(OD) _2$

  4. $CD _4$

Show answer
Correct Option: C
Explanation:

$CaC _{2}+2D _{2}o\rightarrow Ca(OD) _{2}+C _{2}D _{2}$

$D _2O$ can be obtained by:

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

  1. repeated distillation

  2. exchange process

  3. neutron emitting radioactive decay in presence of water

  4. exhaustive electrolysis of alkaline water

Show answer
Correct Option: A,B,D
Explanation:

Heavy water is deuterium oxide $(D _2O)$. Ordinary water contains a fraction (1 in 6000 parts) of heavy water. On large scale, it is produced by repeated electrolysis of ordinary water containing alkali. It is also produced by repeated distillation and condensation. It is also obtained by exchange process.

Heavy water is used as a:

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

  1. fuel in engines

  2. semiconductor

  3. moderator in nuclear reactors

  4. insulator in steam engines

Show answer
Correct Option: C
Explanation:

Heavy metals is used as a moderator in nuclear reactors to bring the fission reaction by slowing down the neutrons and capturing them. The main reason is that the heavy water captures less neutrons than the normal water. Later it can be used as a fuel which has not undergone enrichment to increase the percentage of Uranium-235

$D _{2}O$ is used more in:

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

  1. chemical industry

  2. nuclear moderator

  3. pharmaceutical preparation

  4. insecticide preparations

Show answer
Correct Option: B
Explanation:

Heavy water is used in nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning.

Organic ion exchange resins purify hard water to yield :

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

  1. Distilled water

  2. Only decalcified water

  3. Deionised water

  4. Water having relatively high concentration of $OH^{-}$ion

Show answer
Correct Option: B
Explanation:

Organic ion exchange resins are used for water softening. In this process, the $Ca^{+2}$ and $Mg^{+2}$ ions which cause hardness are exchanged for $Na^{+}$ or $K^{+}$ ions due to which the water becomes decalcified or hardness free. Therefore, organic ion exchange resins purify hard water to yield only decalcified water

Hardness of water can be detected with:

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

  1. $Na _{2}CO _{3}$ solution

  2. soap water

  3. dil. $HCl$

  4. acidified $KMnO _{4}$ solution

Show answer
Correct Option: B
Explanation:

Hardness of water can be detected with soap water. Water is described as being 'hard' if it does not lather readily with soap. 

'Soft water', on the other hand, is described as the one, which lathers readily with soap. Chemically, natural water is never pure and contains varying amounts of the dissolved impurities absorbed from the natural or man made environment. 
When appreciable concentrations of calcium ions $(Ca^{2+})$ or the magnesium ions $(Mg^{2+})$ in the form of their dissolved salts are contained in water, it becomes hard.