Tag: electrochemistry

Questions Related to electrochemistry

When sodium lauryl sulphate is dissolved in water in an appreciable amount, micelle formation takes place. Which of the following options is correct regarding the formation process?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Micelle formation can occur at any temperature

  2. At substantially lower concentrations as concentration increases, conductivity should decrease.

  3. On dilution micelle molar conductance should decrease.

  4. The micelle formation in given case will lead to formation in given case will lead to formation of positively charged colloid.

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Correct Option: B
Explanation:

At substantially lower concentrations as concentration increases , conductivity increases. Micelle formation can occur at above critical micelle concentration which is at 25$^0$C for sodium lauryl sulphate. It doesnt form a positively charged colloid .

The charge required for reducing $1$ mole of $MnO^- _4$ to $Mn^{2+}$ is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $1.93\times 10^5$C

  2. $2.895\times 10^5$C

  3. $4.28\times 10^5$C

  4. $4.825\times 10^5$C

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Correct Option: D
Explanation:
We will write the reactions and do molar analysis to get clear idea of  the solution.
In the following reaction the oxidation state of Mn is changing from +7 to +2.
$MnO^{-} _{4}+5e^{-}\rightarrow Mn^{2+}$
Here, 5 moles of electrons are needed for reduction of 1 mole of $MnO^{-} _4$ to $ Mn^{2+}$
As, 5 moles of elctrons=5 Faradays
$\implies$Quantity of charge required $=5\times96500=4.825\times10^{5} $ Coulombs

Fill in the blank with appropriate words.
The electrolytic solution is always neutral because the total charge on $\underline{(i)}$ is equal to $\underline{(ii)}$ on $\underline{(iii)}$. Unlike the metallic conductor, the electrolyte conducts the electric current by virtue of movement of its $\underline{(iv)}$. The property due to which a metal tends to go into solution in term of positive ions is known as $\underline{(v)}$.
(i), (ii), (iii), (iv) and (v) respectively are:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. cations, partial charge, anions, electrons, reduction

  2. cations, total charge, anions, ions, oxidation

  3. cations, ionic charge, anions, atoms, dissolution

  4. cations, partial charge, anions, molecules, electrolysis

Show answer
Correct Option: B
Explanation:

To maintain neutrality, the total charge on cation is equal to the total charge on anion.

Metallic conductor contains ions. Hence, the current is due to the movement of ions.
Oxidation is the loss of an electron. 
Hence, metals undergo oxidation.
$M\longrightarrow M^{2+}+2e^-$

If equivalent conductance of 1M benzoic acid is $12.8\ { ohm }^{ -1 }{ cm }^{ 2 }$ and if the conductance of benzoate ion and ${ H }^{ -1 }$ ion are 42 and $288.42\ { ohm }^{ -1 }{ cm }^{ 2 }$ respectively. Its degree of dissolution is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. 39%

  2. 3.9%

  3. 0.35%

  4. 0.039%

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Correct Option: B
Explanation:

$\Lambda ^{ 0 } _{ m\left( C _{ 6 }H _{ 5 }COOH \right)  }={ \Lambda  } _{ (C _{ 6 }{ H } _{ 5 }CO{ O }^{ - }) }^{ 0 }\quad +{ \Lambda  }^{ 0 } _{ \left( { H }^{ + } \right)  }$ 

$\ \quad \quad \quad \quad \quad \quad \quad \quad =42+288.42=330.42\ now\quad we\quad have,\ \alpha =\frac { { \Lambda  } _{ m }^{ c } }{ { \Lambda  } _{ m }^{ 0 } } =\frac { 12.8 }{ 330.42 } =3.9$

Which of the following decreases on dilution of electrolyte solution?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Equivalent conductance

  2. Molar conductance

  3. Specific conductance

  4. Conductance

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Correct Option: B
Explanation:

Conductance $=\cfrac{kA}{l}$ 

where, $k$ is conductivity
$k=K\times G$
where, $K$ is cell constant
Does not depend on volume of the solution but molar conductance.
$\wedge _m=\cfrac{K}{C}$
$C$ is concentration which depends on volume. Hence, affected by dilution.

With rise in temperature, electrolytic conductance :

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. increases

  2. decreases

  3. disappear

  4. none of the above

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Correct Option: A
Explanation:

Generally the conductivity of a solution increases with temperature, as the mobility of the ions increases.
Conductivity (or specific conductance) of an electrolyte solution is a measure of its ability to conduct electricity.
Electrolytic conductance generally increases with rise in temperature.

Conductivity of metal decreases with temperature while conductivity of electrolytic conductors  :

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. increases with temperature

  2. slightly decreases with temperature

  3. remains same

  4. slightly increases with temperature

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Correct Option: A
Explanation:

In metals, conductivity is due to movement of free electrons. When temperature increases, the vibration of metal ions increases. This results in increase in resistance of metal and hence, decrease in conductivity. In electrolytic conductors, the ions are charge carriers and with increase in temperature, ionization increases and hence, conductivity increases.

On increasing temperature, the conduction in metallic conductors :

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. increases

  2. decreases

  3. remains constant

  4. none of the above

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Correct Option: B
Explanation:

Increasing the temperature will inhibit conduction in a metallic conductors because the increased thermal motions of the electrons will tend to interfere with their regular flow in an electric current.

The molar conductivity of cation and anion of salt $BA$ are $180$ and $220\ mhos\ cm^{2} mol^{-2}$ respectively. The molar conductivity of $BA$ at infinite dilution is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $90\ mhos \ cm^{2} mol^{-1}$

  2. $110\ mhos \ cm^{2} mol^{-1}$

  3. $400\ mhos \ cm^{2} mol^{-1}$

  4. $200\ mhos \ cm^{2} mol^{-1}$

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Correct Option: C

A solution containing one mole per litre of each $Cu(NO _3) _2$, $AgNO _3, Hg _2(NO _3) _2$ and $Mg(NO _3) _2$ is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts(reduction potential) are.
$Ag^+/Ag=+0.80, Hg^{2+} _2/2Hg =+0.79$
$Cu^{2+}/Cu=+0.34, Mg^{2+}/Mg =-2.37$
With increasing voltage, the sequence of deposition of metals on the cathode will be:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Ag, Hg, Cu, Mg

  2. Mg, Cu, Hg, Ag

  3. Ag, Hg, Cu

  4. Cu, Hg, Ag

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Correct Option: C