Chemistry

Electrochemistry and Solutions

206 Questions

Work through advanced chemistry questions focusing on electrochemistry and properties of solutions. Key themes include electrolytic conductivity, colloidal solutions, and solubility products. These concepts are frequently tested in JEE advanced, NEET, and university level chemistry competitive examinations.

Colloidal solutionsMolar conductivitySolubility productElectrolytic conductivityHydrolysis of saltsEquivalent conductivity

Electrochemistry and Solutions Questions

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

Maximum of 9.72 g of potassium chloride dissolves in 30 g of water at $70^{\circ}$C. The solubility of potassium chloride at $70^{\circ} C$ is:

  1. 3.24 g

  2. 32.4 g

  3. 0.324 g

  4. 33.4 g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solubility is defined as solubility of different substances in grams per 100 gm of water.
30 gm of water dissolves 9.72 g of $KCl$.
So, 100gm will dissolve in $9.72\times 100/30=32.4$ gm.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

What do you understand by the statement "the solubility of copper sulphate in water at $20^{\circ}C$ is 20.7 g" ?

  1. A maximum of 20.7 grams of copper sulphate can be dissolved in 100 ml water at a temperature $20^{\circ}$C.
  2. A maximum of 20.7 grams of copper sulphate can be dissolved in 100 g of water at $20^{\circ}$C.
  3. A maximum of 20.7 grams of copper sulphate can be dissolved in 79.3 g of water at $20^{\circ}$C.
  4. A maximum of 20.7 grams of copper sulphate can be dissolved in 79.3 ml of water at $20^{\circ}$C.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solubility is given in grams per 100 gm of water with temperature and 1 atmospheric pressure.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

At ${25}^{o}C$ the solubility of ${Ag} _{2}{CO} _{3}$ (${K} _{sp}=4.3\times {10}^{-13}$) would be in what order in the following solutions?

  1. $0.01M$ $Ag{NO} _{3}$
  2. $0.04M$ ${K} _{2}{CO} _{3}$

  3. pure water
  4. in a buffer ($pH=4$)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The solubility of Ag2CO3 is suppressed by the common ion effect. Ag+ from AgNO3 will significantly decrease the solubility of Ag2CO3 more than the other options provided.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

$Ca _3(PO _4) _2$ is insoluble in water. On adding a few drops of HCl to solid $Ca _3(PO _4) _2$ in contact with water, the solid dissolves. The reason is?

  1. The solvent becomes more polar on adding HCl
  2. $Ca _3(PO _4) _2$ combines with HCl to form soluble $CaCl _2$
  3. $Ca(H _2PO _4) _2$ is formed, which dissolves
  4. $H _3PO _4$, a weak acid is formed and the solubility product of $Ca _3(PO _4) _2$ decrease
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

What is the solubility of $Al(OH _{3}), K _{sp} = 1 \times 10^{-33}$, in a solution having $pH = 4$?

  1. $6 \times 10^{-3}$M
  2. $10^{-6}$M
  3. $1.5 \times 10^{-4}$M
  4. $2.47 \times 10^{-9}$M
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The solubility equilibrium of $Al(OH) _3$ is

$Al(OH) _3$ ${\rightarrow} _{\leftarrow}$ $Al^{+3}$  + $3OH^-$
Therefore $x=1,\ y=2$ and $K _{sp}$=$[Al^{+3}]\times [OH^-]$ = $27S^4$
$S$ = $(\dfrac{10^{-33}}{27})^{1/4}$
Therefore $S$= $2.47\times 10^{-9}M$ in $ mol\ dm^{-3}$

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

Which of the following is most soluble?

  1. ${Bi} _{2}{S} _{3} \left({K} _{sp} = 1\times {10}^{-17}\right)$
  2. $MnS\left({K} _{sp} = 7\times {10}^{-16}\right)$
  3. $CuS\left({K} _{sp} = 8\times {10}^{-37}\right)$
  4. ${Ag} _{2}S\left({K} _{sp} = 6\times {10}^{-51}\right)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ksp (Solubility product constant) is the equilibrium between a solid and its respective ions in a solution. The value of the constant identifies the degree to which the compound can dissociate in water. The higher the Ksp the more soluble the compound is.
Bismuth is a large ion and sulphur is a small ion, the attractive forces between them are high thus the solubility is high. The solubility product can be calculated as :
$Bi _2S _3$
$K _sp = 1 \times 10^{-17}$
$K _sp = [Bi]^2 [S]^3$
$1 \times 10^{-17} = (2x)^2 (3x)^3 = 108x^5$
$x^5 = \dfrac{1 \times 10^{17}}{108} = 0.000156M $

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

$PbCl _2$ has maximum concentration of $1.0 \times 10^{-3}$ M in its saturated aq. solution at $25^0$C. Its solubility in $0.1$M NaCl solution will be : 

  1. $4 \times 10^{-7}$M
  2. $4 \times 10^{-9}$M
  3. $2 \times 10^{-7}$M
  4. $2 \times 10^{-9}$M
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In saturated aqueous solution :
Maximum concentration in saturated aqueous solution is the solubility (S) of $\displaystyle PbCl _2$

$\displaystyle S=1.0 \times 10^{-3} \ M$

$\displaystyle [PbCl _2]=[Pb^{2+}]=S=1.0 \times 10^{-3} \ M$

$\displaystyle [Cl^-]=2 \times [PbCl _2]= 2 \times  S= 2 \times  1.0 \times 10^{-3} \ M=2.0 \times 10^{-3} \ M$

$\displaystyle K _{sp}=[Pb^{2+}] \times [Cl^-]^2$

$\displaystyle K _{sp}=1 .0 \times 10^{-3} \times [2.0 \times 10^{-3}]^2$

$\displaystyle K _{sp}=4.0 \times 10^{-9}$

In 0.1 M NaCl solution:

$\displaystyle [Cl^-]=[NaCl]=0.1 \ M$

Assuming $Cl^-$ ion from $PbCl _2$ is negligible

$\displaystyle K _{sp}=[Pb^{2+}] \times [Cl^-]^2$

$\displaystyle 4.0 \times 10^{-9}=[Pb^{2+}] \times [0.1]^2$

$\displaystyle [Pb^{2+}]=4.0 \times 10^{-7}  \ M$

Multiple choice chemistry group 2 physical properties of alkaline earth metals alkali metals properties of alkaline earth metals

The sulphate of which metal given below has the highest solubility in water?

  1. $Ca$
  2. $Ba$
  3. $Sr$
  4. $Mg$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

On moving down the group of alkaline earth metals, the solubility of metal sulphates decreases. Also, the ionic size increases and hydration energy of metal ion decreases. Hence, magnesium sulphate($MgSO _4$) has lowest solubility.

Multiple choice chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

If $Na^+$ ion is larger than $Mg^{2+}$ ion, and $S ^{2-}$ion is larger than $Cl^{-}$ ion, which of the following will be less soluble in water?

  1. $NaCl$
  2. $Na _{2}S$
  3. $MgCl _{2}$
  4. $MgS$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The lattice energy of a salt  gives a rough indication of the solubility of the salt in water because it reflects the energy needed to separate the positive and negative ions in a salt. Sodium and potassium salts are soluble in water because they have relatively small lattice energies. Magnesium and aluminum salts are often much less soluble because it takes more energy to separate the positive and negative ions in these salts.

Multiple choice chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

The crystalline salt, $Na _{2}SO _{4}xH _{2}O$ on heating losses $55.9\%$ of its weight. The formula of the crystalline salt is :

  1. $Na _{2}SO _{4}.5H _{2}O$
  2. $Na _{2}SO _{4}.7H _{2}O$
  3. $Na _{2}SO _{4}.10H _{2}O$
  4. $Na _{2}SO _{4}.2H _{2}O$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Na _2SO _4.xH _2O$


Mass of hydrate $=23\times 2+32+64+18x$
$=46+96+18x$
$=142+18x$
Mass of water of hydration=$18x$
% of water in hydrate=$55.9$%

$\cfrac {18x}{142+18x}\times 100=55.9$

$1800x=7937.8+1006.2x$

$793.8x=7937.8$

$x=9.99\sim 10$

Answer= $Na _2SO _4.10H _2O$

Multiple choice chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

The crystalline salt ${ Na } _{ 2 }{ SO } _{ 4 }.x{ H } _{ 2 }O$ on heating loses 55.9% of its mass. The formula of crystalline salt is:

  1. ${ Na } _{ 2 }{ SO } _{ 4 }.5{ H } _{ 2 }O$
  2. ${ Na } _{ 2 }{ SO } _{ 4 }.7{ H } _{ 2 }O$
  3. ${ Na } _{ 2 }{ SO } _{ 4 }.2{ H } _{ 2 }O$
  4. ${ Na } _{ 2 }{ SO } _{ 4 }.10{ H } _{ 2 }O$
  5. ${ Na } _{ 2 }{ SO } _{ 4 }.6{ H } _{ 2 }O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Molar mass of Na2SO4 = 142. Mass of water = 18x. Total mass = 142 + 18x. Water loss = 18x / (142 + 18x) = 0.559. Solving for x gives x = 10.

Multiple choice chemistry substances in common use percent composition water of crystallisation percentage composition and empirical formula

Potash alum contains ___________ number of water molecules.

  1. 24

  2. 22

  3. 20

  4. 25
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Potash Alum $(K _2SO _4 Al _2 (SO _4) _3 .24H _2O)$ is a colourless, odourless and crystalline substance. Its crystals are prepared by mixing concentrated solutions of potassium sulphate and aluminium sulphate. It is soluble in water. It contains 24 molecules of water.