Tag: hydrogen and its compounds

Questions Related to hydrogen and its compounds

Which one of the following statements is correct about $D _{2}O$ and $H _{2}O$?

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

  1. $D _{2}O$ has lower dielectric constant than $H _{2}O$

  2. $NaCl$ is more soluble in $D _{2}O$ than in $H _{2}O$

  3. Both (a) and (b) are correct

  4. None of the above

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Correct Option: A

A water sample has ppm concentrations of the following metals

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

  1. Fe=0.2

  2. Mn=0.2

  3. Al=0.2

  4. Cu=0.2

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Correct Option: B

Heavy water is used in atomic reactor as:

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

  1. coolant

  2. moderator

  3. both coolant and moderator

  4. neither coolant nor moderator

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Correct Option: C
Explanation:

In atomic reactor, heavy water is used as coolant and moderator. As a coolant, it removes heat from the reactor and as a moderator, it slows down the speed of neutrons.

Which one of the following processes will produce hard water?

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

  1. Saturation of water with $CaCO _3$

  2. Addition of $Na _2SO _4$ to water.

  3. Saturation of water with $MgCO _3$

  4. Saturation of water with $CaSO _4$

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Correct Option: A,C,D
Explanation:

Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of calcium and magnesium-containing minerals such as limestone, chalk and dolomite.
The following processes will produce hard water
1. saturation of water with $CaCO _3$
2. saturation of water with $MgCO _3$
3. saturation of water with $CaSO _4$
Hence options A,B & D are correct.

$D _2O$ differ in the following except:

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

  1. freezing point

  2. density

  3. ionic product of water

  4. its reaction with sodium

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Correct Option: D
Explanation:

The freezing point of water is $0 ^oC$, whereas the freezing point of heavy water is $3.8 ^0C$. 


At $20 ^0C$, the density of water is $0.9982$ g/mL, whereas the density of heavy water is $1.1056$ g/mL. 

Similarly, water and heavy water differ in the value of the ionic product. 

However, the chemical properties (such as reaction with sodium) of water are similar to that of heavy water due to the same electronic configuration.

$CH _3CH _2MgCl$ when reacts with heavy water, the product obtained is:

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

  1. $CD _3-CH _2 D$

  2. $CH _3 CH _2 - OD$

  3. $CD _3 - CD _3$

  4. $CH _3 CH _2 D$

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Correct Option: D
Explanation:

The reaction of ethylmagnesium chloride with heavy water forms mono deuterated ethane. $CH _3CH _2MgCl + DOD \rightarrow CH _3CH _2D + MgClOD$.

During electrolysis bonds in $H _2O$ are broken 18 times faster than $D _2O$.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Due to the light weight of protium than deuterium, a bond to a protium atom can be broken $18$ times faster than the bond to a deuterium atom.

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

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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

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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 $H _{2}O$

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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 $(16+1+1=18)$.