Tag: hard water and soft water

Questions Related to hard water and soft water

What 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. $Ca _{2}D _{2}O$

  4. $CD _{2}$

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Correct Option: A
Explanation:

Calcium carbide reacts with ordinary water and acetylene forms, similarly calcium carbide reacts with heavy water and  deuterated acetylene $C _{2}D _{2}$ forms.
Reaction:

$CaC _2+2D _2O\rightarrow C _{2}D _{2}$ + $Ca(OD) _2$

Some statements about heavy water are given below:
$(a):$Heavy water is used as a moderator in nuclear reactions
$(b):$Heavy water is more associated than ordinary water
$(c):$Heavy water is more effective solvent than ordinary water
Select correct statements:

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

  1. $(a),:(b):and:(c)$

  2. $(b):and:(c)$

  3. $(a):and:(c)$

  4. $(a):and:(b)$

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Correct Option: D
Explanation:

Heavy water is $D _2O$, it has higher molar mass than water.
It 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.
Also, dielectric constant of $D _2O$ is lower than water so solubility of inorganic substances is greater in$H _{2}O$ than $D _{2}O$.

$D _{2}O$ is:

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

  1. product of $O _{2}$ and $H _{2}$

  2. simple water in which present heavy metal salts

  3. marine water

  4. water which form redistillation and condensation

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Correct Option: D
Explanation:
$D _{2}O$ is heavy water, which is a product of $O _{2}$ and $D _{2}$. Heavy water form redistillation and condensation.

Of the two solvent ${ H } _{ 2 }O$ and ${ D } _{ 2 }O$, $NaCl$ dissolves:

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

  1. equally in both solvents

  2. only in ${ H } _{ 2 }O$ but remains insoluble in ${ D } _{ 2 }O$

  3. more in ${ D } _{ 2 }O$

  4. more in ${ H } _{ 2 }O$

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Correct Option: D
Explanation:

$NaCl$ (and other ionic compounds) dissolve more in $H _2O$ than in $D _2O$ as the dielectric constant of $H _2O$ $(78.39)$ is higher than the dielectric constant of $D _2O:(78.06)$. This is due to lower molar mass of $H _2O$ as compared to that of $D _2O$.

Which of the following is not the possible enol form of propanone in the presence of heavy water?

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

  1. ${ CH } _{ 3 }-CD=\overset { \overset { OD }{ | } }{ C } -D$

  2. ${ CH } _{ 3 }-\overset { \overset { OD }{ | } }{ C= } CHD$

  3. ${ CH } _{ 2 }=\overset { \overset { OD }{ | } }{ C- } { CD } _{ 3 }$

  4. ${ CD } _{ 2 }=\overset { \overset { OD }{ | } }{ C- } { CD } _{ 3 }$

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Correct Option: A

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.