Chemistry

Electrochemistry and Solutions

205 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

$Ca _3(PO _4) _2$ 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
C Correct answer
Explanation

Calcium phosphate is a salt of a weak acid (phosphoric acid). Adding hydrochloric acid introduces strong H+ ions that combine with phosphate ions to form soluble calcium dihydrogen phosphate or phosphoric acid, causing the solid to dissolve.

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

The solubility of $A {2}X _{3}$ is $y$ $mol$ $dm^ {-3}$. Its solubility product is ____________.

  1. $6y^ {4}$
  2. $64y^ {4}$
  3. $36y^ {5}$
  4. $108y^ {5}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For a salt A2X3 dissociating into 2A(3+) and 3X(2-), if solubility is y, [A(3+)] = 2y and [X(2-)] = 3y. The solubility product Ksp = (2y)^2 * (3y)^3 = 4y^2 * 27y^3 = 108y^5.

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.

Multiple choice aluminium patterns and properties of metals chemistry

${ AlO } _{ 2 }^{ - }$ ion in aqueous solution exists as ?

  1. ${ \left[ Al{ \left( OH \right) } _{ 6 } \right] }^{ 2- }$
  2. ${ \left[ Al{ \left( OH \right) } _{ 4 }\left( { H } _{ 2 }O \right) \right] }^{ - }$
  3. ${ \left[ Al{ \left( OH \right) } _{ 4 }{ \left( { H } _{ 2 }O \right) } _{ 2 } \right] }^{ - }$
  4. ${ \left[ Al{ \left( OH \right) } _{ 6 } \right] }^{ - }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In aqueous solution, the aluminate ion AlO2- is hydrated and exists as the octahedral complex [Al(OH)4(H2O)2]-.

Multiple choice aluminium patterns and properties of metals chemistry

Aluminium chloride exists as dimer, $Al _{2}Cl _{6}$ in solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives:

  1. $[Al(OH) _{6}]^{3-} + 3HCl$
  2. $Al _{2}O _{3} + 6HCl$
  3. $Al^{3+} + 3Cl^{-}$
  4. $[Al(H _{2}O) _{6}]^{3+} + 3Cl^{-}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When ${ Al } _{ 2 }{ Cl } _{ 6 }$ is dissolved in water, it is ionized to form ${ \left[ Al{ \left( { H } _{ 2 }O \right)  } _{ 6 } \right]  }^{ 3+ }$ and ${ Cl }^{ \left( - \right)  }$ due to large hydration energy of ${ Al }^{ 3+ }$.

${ Al } _{ 2 }{ Cl } _{ 6 }+12{ H } _{ 2 }O\rightleftharpoons 2{ \left[ Al{ \left( { H } _{ 2 }O \right)  } _{ 6 } \right]  }^{ 3+ }+{ 6Cl }^{ \left( - \right)  }$