Tag: chemical reactions

Questions Related to chemical reactions

Which among the following solutions is NOT used in determination of the cell constant?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. ${ 10 }^{ -2 }MKCl$

  2. ${ 10 }^{ -1 }MKCl$

  3. $1 M KCl$

  4. Saturated $KCl$

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Correct Option: D

Metallic conduction involves:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. no chemical change

  2. flow of electrons

  3. transfer of matter

  4. conductance decreases with increase in temperature

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Correct Option: B,D
Explanation:

The substances which allow the flow of electric current are called conductors. The good metal conductors are copper, silver, tin, etc. 


It is due to the flow of electrons. It is not accompanied by the decomposition of the substance, only physical changes occur. It also does not involve the transfer of matter it is due to the flow of electrons. 

Conductivity decreases with an increase in temperature due to an increase in the number of collisions.

Hence, the correct options are $B$ and $D$

In Death valley,California,a conduction process was going on in an air conditioned room maintained at $30^0$.Suddenly there was a power cut and temperature started to rise and it was found that the conduction process got slower.The conduction type can be:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. electrolytic

  2. metallic

  3. any of these

  4. none of these

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Correct Option: B
Explanation:

As temperature rises, thermal conductivity of metals decreases due to increase in molecular collisions.

Ionic conductance of ${ H }^{ + }$ and ${ SO } _{ 4 }^{ 2- }$ are $x$ and $yS\ { cm }^{ 2 }\ { mol }^{ -1 }$. Hence, equivalent conductivity of ${ H } _{ 2 }{ SO } _{ 4 }$ is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $2x+\cfrac { y }{ 2 } $

  2. $x+\cfrac { y }{ 2 } $

  3. $\cfrac { x }{ 2 } +y$

  4. $\cfrac { x }{ 2 } +\cfrac { y }{ 2 } $

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Correct Option: A
Explanation:

Equivalent conductance can be defined as the conductance produce by an equivalent of ion present in the solution.

For ${ H }^{ + }$, no.of ${ e }^{ - }$ change $=1$
For ${ SO } _{ 4 }^{ 2- }$, no.of ${ e }^{ - }$ change $=2$
Thus equivalent conductance of ${ H } _{ 2 }{ SO } _{ 4 }$
${ H } _{ 2 }{ SO } _{ 4 }$ $\rightleftharpoons 2{ H }^{ + }+{ SO } _{ 4 }^{ 2- }$
Eg Conductance $=\cfrac { 2[Ionic\quad conductance\quad of\quad { H }^{ + }] }{ nf } +\cfrac { Ionic\quad Conductance\quad of\quad { SO } _{ 4 }^{ 2- } }{ nf } $
Eg. Conductance $=2\times \cfrac { x }{ 1 } s{ cm }^{ 2 }+\cfrac { y }{ 2 } s{ cm }^{ 2 }$
Eg. Conductance $=2x+\cfrac { y }{ 2 }$

In passing $3\ F$ of electricity through three electrolytic cells connected in series containing $Ag^{\oplus}, Ca^{2+}$, and $Al^{3+}$ ions, respectively. The molar ratio in which the three metal ions are liberated at the electrodes is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $1 : 2 : 3$

  2. $2 : 3 : 1$

  3. $6 : 3 : 2$

  4. $3 : 4 : 2$

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Correct Option: C
Explanation:

For all the solution $Q=i\times t$ is same,

${ n } _{ Ag }=\cfrac { Q }{ nF } =\cfrac { Q }{ F } ({ Ag }^{ + }+{ e }^{ - }\longrightarrow Ag)$
${ n } _{ Ca }=\cfrac { Q }{ 2F } ({ Ca }^{ 2+ }+2{ e }^{ - }\rightarrow Ca)$
${ n } _{ Al }=\cfrac { Q }{ 3F } ({ Al }^{ 3+ }+3{ e }^{ - }\rightarrow Al)$
$\therefore $ ${ n } _{ Ag }:{ n } _{ Ca }:{ n } _{ Al }=1:\cfrac { 1 }{ 2 } :\cfrac { 1 }{ 3 } =6:3:2$
$\therefore $   Molar ratio$=6:3:2$.

Which of the following statement is incorrect with respect to metallic or electronic conductivity ?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Metallic conductivity depends on the number of electrons in the valence shell of an atom of metal

  2. Metallic conductivity depends on the structure of metal and its characteristics

  3. The electrical conductivity of metal increases with increase in temperature

  4. There is no change in the structure of metal during electrical conduction

Show answer
Correct Option: C
Explanation:

Metallic or electronic conductivity is due to the presence of free electrons or/and holes (positive charge). It depends upon:
(i) Number of valence electrons present in the metal 
(ii) Structure and nature (characteristic) of metal 
(iii) Density of metal 
(iv) Temperature 


With increase in temperature, electronic conductivity decreases because the arrangement of electrons gets disturbed. Metallic conductivity does not affect the structure of the metal. 

At infinite dilution equivalent conductances of $B{ a }^{ +2 }$ & $C{ 1 }^{ - }$ ions are $127$ & $76\ oh{ m }^{ -1 }c{ m }^{ -1 }\ e{ q }^{ -1 }$ respectively. Equivalent conductance of $BaCl _{ 2 }$ at infinite dilution is:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. $139.5$

  2. $101.5$

  3. $203$

  4. $279$

Show answer
Correct Option: D
Explanation:

${ \Lambda  } _{ eq }^{ \infty  }\left( { Ba }^{ 2+ } \right) =127{ \Omega  }^{ -1 }{ cm }^{ -1 }{ eq }^{ -1 }\ { \Lambda  } _{ eq }^{ \infty  }\left( { Cl }^{ - } \right) =76{ \Omega  }^{ -1 }{ cm }^{ -1 }{ eq }^{ -1 }\ { \Lambda  } _{ eq }^{ \infty  }\left( { Ba }{ Cl } _{ 2 } \right) ={ \Lambda  } _{ eq }^{ \infty  }\left( { Ba }^{ 2+ } \right) +2{ \Lambda  } _{ eq }^{ \infty  }\left( { Cl }^{ - } \right) \ \qquad \qquad \quad =127+76\times 2\ \qquad \qquad \quad =279{ \Omega  }^{ -1 }{ cm }^{ -1 }{ eq }^{ -1 }$

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

Show answer
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

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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.
$M\longrightarrow M^{2+}+2e^-$