Tag: water

Questions Related to water

${ H } _{ 3 }{ PO } _{ 4 }$ is a tribasic acid and one of its salt is ${ NaH } _{ 2 }{ PO } _{ 4 }$ What volume of $1M\quad NaOH$ solution should be added to $12g\ { NaH } _{ 2 }{ PO } _{ 4 }$ to convert it into ${ Na } _{ 3 }{ PO } _{ 4 }$? ($at.wt$ of $P=31$)

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $100\ ml$

  2. $200\ ml$

  3. $80\ ml$

  4. $300\ ml$

Show answer
Correct Option: B
Explanation:

$Na{ H } _{ 2 }{ PO } _{ 4 }+NaOH\rightarrow { Na } _{ 2 }{ HPO } _{ 4 }+{ H } _{ 2 }O\quad \quad -(i)$

Moles$=\cfrac { 12 }{ 120 } $    $\cfrac { 12 }{ 120 } $            $\cfrac { 12 }{ 120 } $
${ Na } _{ 2 }{ HPO } _{ 4 }+NaOH\rightarrow { Na } _{ 3 }{ PO } _{ 4 }+{ H } _{ 2 }O\quad \quad \quad -(ii)$
Moles$=\cfrac { 12 }{ 120 } $     $\cfrac { 12 }{ 120 } $           $\cfrac { 12 }{ 120 } $
Moles of $NaOH$ required $=\cfrac { 12 }{ 120 } +\cfrac { 12 }{ 120 } $
                                              $=0.2$ moles
Now, $Mularity=\cfrac { Moles }{ Vol.of\quad sol\quad in\quad ltrs } $
$\therefore $ Volume of $NaOH$ solution $=\cfrac { 0.2 }{ 1 } $
                                                  $=0.2$ litres
                                                  $=200$ml

The $K _{sp}$ of $Ag _{2}CrO _{4}, AgCl, AgBr$ and $AgI$ are respectively, $1.1\times 10^{-12}$, $1.8\times 10^{-10}$, $5.0\times 10^{-13}$ and $8.3\times 10^{-17}$. Which of the following salts will precipitate last if $AgNO _{3}$ solution is added to the solution containing equal moles of $NaCl, NaBr, NaI$ and $Na _{2}CrO _{4}$?

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $Ag _{2}CrO _{4}$

  2. $AgI$

  3. $AgCl$

  4. $AgBr$

Show answer
Correct Option: A
Explanation:
  1. $Ag _2CrO _4\rightleftharpoons 2Ag^++{CrO _4}^{2-}$

    $Ksp=(2s)^2\times s=4s^2$

    $Ksp=(1.1\times 10^{-12})$

    $S=3\sqrt {\cfrac {Ksp}{4}}=6.5\times 10^{-5}$M

    2. $AgCl\rightleftharpoons Ag^++Cl^-$

    $Ksp=S\times S$  ;       $Ksp=1.8\times 10^{-10}$

    $S=\sqrt {Ksp}=1.34\times 10^{-5}$M

    3. $AgBr\rightleftharpoons Ag^++Br^-$

    $Ksp=S\times S$ ;     $Ksp=5\times 10^{-13}$

    $S=\sqrt {Ksp}=0.71 \times 10^{-6}$M

    4. $AgI\rightleftharpoons Ag^++I^-$

    $Ksp=S\times S$  ;    $Ksp=8.3\times 10^{-17}$

    $S=\sqrt{Ksp}=0.9\times 10^{-8}$M

    $\therefore$ Solubility of $Ag _2CrO _4$ is highest, so it will precipitate last.

Dissolution of salt participate in water shows:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. Particulate nature of matter.

  2. Continuous nature of matter.

  3. Particle size of salt is very big.

  4. All of these.

Show answer
Correct Option: A
Explanation:

The salt will dissolve and water will taste salty. Salt particles dissolve in water because they occupy the spaces between the water molecules resulting in spreading of salt particles throughout the particles of water showing particle nature of matter.

An aqueous solution of zinc sulphate is acidic in nature because______.


chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $ZnSO _{4}$ ionizes

  2. $SO _{4}^{-2}$ reacts with $H _{2}O$

  3. $Zn^{+2}$ reacts with $H _{2}O$

  4. $Zn^{+2}$ & $SO^{-2} _{4}$ reacts with $H _{2}O$

Show answer
Correct Option: D

KMnO$ _4$ oxidises X$^{n+}$ ion to XO$^- _3$ itself changing into Mn$^{+2}$ in acid solution. $2.68$ $\times$ $10^{-3}$ mole of X$^{n+}$ requires $1.61$ $\times$ $10^{-3}$ mole of MnO$ _4^-$. The value of n is :

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $1$

  2. $2$

  3. $4$

  4. $3$

Show answer
Correct Option: B

Which of the following does not undergo hydrolysis?

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $BF _3$

  2. $NaCl _3$

  3. $NF _3$

  4. All of these

Show answer
Correct Option: C
Explanation:
$(C)\ NF _{3}$
Because it does not have any vacant orbitals to accept lone pair 
$\therefore $ do not under go nudolysis.






Solution of $ FeCI _3 $ and $ H _2O $ is :

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. Basic

  2. Acidic

  3. Neutral

  4. None of these

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Correct Option: B

Salt which on heating produces a mixture of two gases is :

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $NaNO3$

  2. $Bi(NO3)3$

  3. $Pb(NO3)2$

  4. $NH4NO3$

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Correct Option: A

The mass in grams of potassium permanganate (MM = 158) crystals required to oxidise $750\,\,c{m^3}$ of 0.1 M Mohr's salt solution in acidic medium is about 

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. 11.8

  2. 5.8

  3. 6.0

  4. 2.4

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Correct Option: A

Degree of hydrolysis for a salt of weak acid and strong base can be changed by 

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. Increasing concentration of salt

  2. Increasing temperature

  3. Adding base

  4. All of these

Show answer
Correct Option: D