Tag: electrochemistry

Quizzes (9) Questions (132)

Questions Related to electrochemistry

Multiple choice conductivity and its types electrochemistry

What do you mean by equivalent Conductivity?

  1. It is defined as the conducting power of all the ions produced by dissolving one gram equivalent of an electrolyte in solution.

  2. It is defined as the conducting power of all the ions produced by dissolving ten gram equivalent of an electrolyte in solution.

  3. It is defined as the conducting power of all the ions produced by dissolving hundred gram equivalent of an electrolyte in solution.

  4. It is defined as the conducting power of all the ions produced by dissolving thousand gram equivalent of an electrolyte in solution.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Equivalent Conductivity is defined as the conducting power of all the ions produced by dissolving one gram equivalent of an electrolyte in solution. It is expressed as and is related to specific conductance as. (M is Molarity of the solution)

Multiple choice conductivity and its types electrochemistry

The resistance of $1\ N$ solution of $CH _{3}COOH$ is $250\ ohm$ when measured in a cell of cell constant $1.15\ cm^{-1}$. The equivalent conductance will be:

  1. $4.6\ ohm^{-1} cm^{2} eq^{-1}$
  2. $9.2\ ohm^{-1} cm^{2} eq^{-1}$
  3. $18.4\ ohm^{-1} cm^{2} eq^{-1}$
  4. $0.023\ ohm^{-1} cm^{2} eq^{-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$K = C \times \dfrac {l}{A} = \dfrac {1}{250}\times 1.15 = 4.6\times 10^{-3}\ ohm^{-1} cm^{-1}$
$\wedge _{e} = K\times \dfrac {1000}{N} = 4.6\times 10^{-3} \times \dfrac {1000}{1} = 4.6\ ohm^{-1} cm^{2} eq^{-1}$.

Multiple choice conductivity and its types electrochemistry

The specific conductance of a $0.01\ M$ solution of $KCl$ is $0.0014\ ohm^{-1} cm^{-1}$ at $25^{\circ}C$. Its equivalent conductance is____________.

  1. $14$
  2. $140$
  3. $1.4$
  4. $0.14$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\kappa =0.0014\ S{ cm }^{ -1 }\ \Lambda _{ eq }=\cfrac { 1000\times \kappa  }{ C } \ C=0.01M\ { \Lambda  } _{ eq }=\cfrac{1000 \times 0.0014}{0.01}=140$

Multiple choice conductivity and its types electrochemistry

The resistance of a N/10 KCI solution is 245$\Omega $. Calculate the equivalent conductance of the solution if the electrodes in the cell are 4cm apart and each having an area of 7.0sq,cm.

  1. $23.32S{ cm }^{ 2 }{ eq }^{ -1 }$
  2. $23.23S{ cm }^{ 2 }{ eq }^{ -1 }$
  3. $2.332S{ cm }^{ 2 }{ eq }^{ -1 }$

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given resistance = 245$\Omega $

Formula for the specific conductance (K) = $ \dfrac{1}{R} $ $\times \dfrac{l}{a}$
= $ \dfrac{1}{245} $ $\times \dfrac{4}{7}$
 K = 2.33 $\times 10^-$$^3$ 
Formula for the euivalent conductance=  K $\times$ $\dfrac{1000}{C}$
= 2.33 $\times 10^-$$^3$ $\times 10000$
= 23.32S $cm^2$ eq $^-$$^1$

Multiple choice conductivity and its types electrochemistry

The equivalent conductance of a weak monobasic acid at infinite dilution is $100cm^3$ $eq^{-1}$ and that of its $0.01$M solution is $5cm^2$ $eq^{-1}$ at $25^o$C. The dissociation constant $K _a$ of the acid is:

  1. $2.5\times 10^{-4}$
  2. $5\times 10^{-4}$
  3. $1.25\times 10^{-5}$
  4. $2.5\times 10^{-5}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The degree of dissociation, $\alpha=\cfrac {\text{Equivalent conductance at given dilution}}{\text{Equivalent conductance at infinite dilution}}$

                                                   $=\cfrac {5cm^2eq^{-1}}{100cm^2eq^{-1}}=\cfrac {1}{20}$
For weak monobasic acid,
$K _a=\cfrac {C \alpha^2}{1-\alpha}$
       $=C\alpha^2(\because 1>> \alpha)$
       $=0.01\times \left(\cfrac {1}{20}\right)^2= 2.5 \times 10^{-5}$

Multiple choice conductivity and its types electrochemistry

Equivalent conductance and molar conductance of $Fe _2(SO _4) _3$ are related?

  1. $\bigwedge _e=\bigwedge _m$
  2. $\bigwedge _{eq} = \dfrac{\bigwedge _m}{3}$
  3. $\bigwedge _{eq} = 3 \bigwedge _m$
  4. $\bigwedge _{eq} = \dfrac{\bigwedge _m}{6}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For Fe2(SO4)3, the salt dissociates into 2 Fe^3+ and 3 SO4^2- ions. The total charge is 6. The relationship between equivalent conductance and molar conductance is Lambda_eq = Lambda_m / n, where n is the total charge (valency factor). Here n = 6.

Multiple choice conductivity and its types electrochemistry

Molar ionic conductance of ${Ca}^{+2}$ is $x$ $S{m}^{2}$ ${mole}^{-1}$. Equivalent conductance of calcium phosphate is ____ $S{m}^{2}g$ ${eq}^{-1}$

  1. $x+y$
  2. $(3x+2y)$
  3. $6(3x+2y)$
  4. $\cfrac{3x+2y}{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Calcium phosphate $\rightarrow { Ca } _{ 3 }{ \left( { PO } _{ 4 } \right)  } _{ 2 }$

ionic conductance of ${ Ca }^{ 2+ }=x$ ${ sm }^{ 2 }{ mol }^{ -1 }$
ionic conductance of ${ PO } _{ 4 }^{ 3- }=Y$ ${ sm }^{ 2 }{ mol }^{ - }$
${ Ca } _{ 3 }{ \left( { PO } _{ 4 } \right)  } _{ 2 }\rightarrow 3{ Ca }^{ 2+ }+2{ PO } _{ 4 }^{ 3- }$
$\therefore $  equivalent conductivity $=x+y$

Multiple choice conductivity and its types electrochemistry

Which of the following has least conductivity in aqueous solution?

  1. $CO(NH _3) _4Cl _3$
  2. $Co(NH _3) _3Cl _3$
  3. $Co(NH _3) _5Cl _3$
  4. $Co(NH _3) _6Cl _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Conductivity $\alpha $ no. of ions dissociated in solution.

$Co{ \left( { NH } _{ 3 } \right)  } _{ 4 }{ Cl } _{ 3 }\rightarrow { \left[ Co{ \left( { NH } _{ 3 } \right)  } _{ 4 }{ Cl } _{ 2 } \right]  }^{ + }+{ Cl }^{ \left( - \right)  }$
                                                    2 ions
$Co{ \left( { NH } _{ 3 } \right)  }{ Cl } _{ 3 }\rightarrow \left[ Co\left( { NH } _{ 3 } \right) { \left( Cl \right)  } _{ 3 } \right] $
                                                          1 ion
$Co{ \left( { NH } _{ 3 } \right)  } _{ 5 }{ Cl } _{ 3 }\rightarrow { \left[ Co{ \left( { NH } _{ 3 } \right)  } _{ 5 }Cl \right]  }^{ 2+ }+2{ Cl }^{ \left( - \right)  }$
                                                          3 ions
$Co{ \left( { NH } _{ 3 } \right)  } _{ 6 }{ Cl } _{ 3 }\rightarrow { \left[ Co{ \left( { NH } _{ 3 } \right)  } _{ 6 } \right]  }^{ 3+ }+3{ Cl }^{ \left( - \right)  }$
                                                             4 ions
$\therefore  Co{ \left( { NH } _{ 3 } \right)  } _{ 6 }{ Cl } _{ 3 }$ has highest conductivity.

Multiple choice conductivity and its types electrochemistry

The equivalent conductance of $CH _3COONa, \ HCl$ and $NaCl$ at infinite dilution are $91, 426$ and $126 \ S \ cm^3 \ eq^{-1}$ respectively at $25^oC$. The equivalent conductance of $1 \ M \ CH _3COOH$ solution is $19.55 \ S \ cm^2 \ eq^{-1}$. The pH of the solution is:

  1. $5.3$
  2. $4.3$
  3. $2.3$
  4. $1.3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\lambda^o _{CH _3COONa}= \lambda^o _{CH _3COO^-}+ \lambda^o _{Na}=91 \ Scm^2eq^{-1}$.....(i)

$\lambda^o _{HCl}= \lambda^o _{H}+ \lambda^o _{Cl^-}= 426 \ Scm^2eq^{-1}$.....(ii)

$\lambda^o _{NaCl}= \lambda^o _{Na}+ \lambda^o _{Cl^-}=126 \ Scm^2eq^{-1}$.....(iii)

$\lambda^o _{CH _3COOH}= \lambda^o _{CH _3COO^-}+ \lambda^o _{H^+}= (i) + (ii) – (iii) = 391 \ Scm^2eq^{-1}$

$ \lambda _{CH _3COOH}= 19.5 \ Scm^2eq^{-1}$ (given)

Degree of dissociation $= \cfrac {\lambda _m}{\lambda^o _m}= \cfrac {19.55}{391}=0.05$

$CH _3COOH \longrightarrow CH _3COO^- + H^+$

$1(1-0.05)$                $0.05$             $0.05$

$[H^+]=0.05 \ M$

$pH= -log [H^+]=1.3$

Multiple choice conductivity and its types electrochemistry

The electrolytic conductance is a direct measure of:

  1. resistance

  2. potential

  3. concentration

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

By measuring conductance, we can measure resistance, by using formula.

$R=\cfrac{1}{C}$             C=conductance