Tag: chemistry

Questions Related to chemistry

The weight of one mole of heavy water is:

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

  1. $18$ gm

  2. $20$ gm

  3. $19$ gm

  4. $21$ gm

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Correct Option: B
Explanation:
 Deuterium is called as heavy water,

As atomic mass of Deuterium is 2 and atomic mass of oxygen is 16

So Molar mass of $D _2O$ is = $2\times2 +1\times 16= 20$

Weight of $1$ mole of ${ D } _{ 2 }O =$ Molecular mass of ${ D } _{ 2 }O = 20$ gm

Option B is correct.

$D _2O$ ( heavy water) and $H _2O$ differ in 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. None of these

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Correct Option: D

Deuterio hydrate of magnesium sulphate contains how many molecules of heavy water?

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

  1. $2\ D _{2}O$

  2. $3\ D _{2}O$

  3. $10\ D _{2}O$

  4. $7\ D _{2}O$

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Correct Option: D
Explanation:

Deuterio hydrate of magnesium sulphate is $MgSO _4.7D _2O$. So, 7 molecules of heavy water molecules is present.

$4D _{2}O+3Fe \xrightarrow{Red:hot}Fe _{3}O _{4}+gas$. The gas produced in the above reaction is:

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

  1. $O _{2}$

  2. $H _{2}$

  3. $D _{2}$

  4. $T _2$

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Correct Option: C
Explanation:

Reaction of process:
$4D _{2}O+3Fe \xrightarrow{Red:hot}Fe _{3}O _{4}+ 4D _2$.

Heavy water is not used for drinking because:

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

  1. it is poisonous

  2. it is costly

  3. its physiological action is different from ordinary water

  4. its chemical properties different from ordinary water

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Correct Option: C
Explanation:

As molecular mass of heavy water is higher than water so its physiological action is different from ordinary water and because of that reason it can not be used as drinking water.

Which of the following are correctly matched?


$(a):D _{2}O-$ Hard water

$(b):H _{2}O-$ Heavy water

$(c):D-$ Heavy hydrogen

$(d):BaO _{2}.8H _{2}O-$ True peroxide

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

  1. $a, b, c, d$ are correct

  2. $c, d$ are correct

  3. $a, b, c$ are correct

  4. $a, c, d$ are correct

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Correct Option: B
Explanation:

$D _{2}O-$ Heavy water


$H _{2}O-$ Ordinary water

$D-$ Heavy hydrogen (As atomic mass of $D$ is higher than $H$)

$BaO _{2}.8H _{2}O-$ True peroxide.

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

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

  1. $0^\circ C$

  2. $-3.8^\circ C$

  3. $0.8^\circ C$

  4. $3.82^\circ C$

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Correct Option: D
Explanation:

Freezing point of heavy water is $3.82^oC$. Heavy water is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium, rather than the common hydrogen-$1$ isotope that makes up most of the hydrogen in regular water.

Which of the following is not true?

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

  1. Ordinary water is electrolysed more rapidly than $D _{2}O$

  2. $D _{2}O$ freezes at lower temperature than $H _{2}O$

  3. Reaction between $H _{2}$ and $Cl _{2}$ is much faster than $D _{2}$ and $Cl _{2}$

  4. Bond dissociation energy for $D _{2}$ is greater than $H _{2}$

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Correct Option: B
Explanation:

As D contains one extra neutron so heavy water has higher molecular mass than water and its electrolysis takes more time.
Also because of that it is less reactive and bond dissociation energy for $D _{2}$ is greater than $H _{2}$.
And $D _{2}O$ freezes (3.8C) at higher temperature than $H _{2}O$

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 $D _{2}O$.