Tag: metallic and electrolytic conduction

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Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Electrical conductivity of $Se$ is negligible in dark but increases to exposure to light. Because of this property it is used in:

  1. photoelectric cells

  2. semiconductors

  3. high voltage batteries

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

In photoelectric cells, light energy is converted into electrical energy .Thus $Se$ is used in photocells because of its behaviour to become a conductor in presence of light.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Pure water is a good conductor of electricity.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For pure water ${ K } _{ a }=1.8\times { 10 }^{ -16 }$ at $25℃$

Since dissociation constant is very very low.
So pure water doesn't conduct electricity. Because free ions are not present in sufficient amount for conduction.
${ H } _{ 2 }{ O\rightleftharpoons  }{ H }^{ + }+{ OH }^{ - }$ (weak dissociation constant)

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Molten sodium chloride conducts electricity due to presence of:

  1. free electrons

  2. free ions

  3. free molecules

  4. free atoms
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Molten sodium chloride conducts electricity due to the presence of free ions.
In order to conduct electricity a substance must have charge particles, such as electrons and ions, that are free to move freely through it. In the solid state, ionic compounds such as sodium chloride have their ions fixed in position and therefore these ions cannot move so solid ionic compounds cannot conduct electricity. However in the molten state, ions in ionic compounds are free to flow and therefore molten sodium chloride can conduct electricity.
Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Metallic conduction depends upon which of the following?

  1. The nature of the metal

  2. Number of valence electrons per atom

  3. Density of metal

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

For metals the thermal conductivity is mainly a function of the motion of free electrons.As the temperature increases the molecular vibrations increases so they obstruct the free flow of electrons thus reducing conductivity.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

How much time is required for the complete decomposition of 2 moles of water using a current of 2 ampere?

  1. 26.805 h

  2. 153.61 h

  3. 107.22 h

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Solution:- (D) none of these
$2 {H} _{2}O \longrightarrow 2 {H} _{2} + {O} _{2}$
From the above reaction-
$1$ mole of ${H} _{2}O$ exchanges $2$ moles of electrons, then $2$ moles of ${H} _{2}O$ will exchange $4$ moles of electrons.
From Faraday's law of electrolysis,
$q = nF$
$\Rightarrow i \times t = nF \; \left( \because q = i \times t \right)$
$\Rightarrow t = \cfrac{nF}{i} = \cfrac{4 \times 96500}{2} = 193000 \; s = 53.61 \; hr$
Hence the time required is $53.61$ hours.
Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

A dilute solution of $H _2SO _4$ was electrolyzed by passing a current of 2 amp. The time required for formation of 0.5 mole of oxygen is:

  1. 26.8 hours

  2. 13.4 hours

  3. 6.7 hours

  4. 28.6 hours
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Let current of $2$ amp is passed through the solutions for $t$ seconds
$\therefore$   Charge passed $=2\times t$

$\therefore$   moles of electrons passed $=\dfrac { 2t }{ 96500 } $
At anode :

${ 2OH }^{ \left( - \right)  }\rightarrow 1/2{ O } _{ 2 }+{ H } _{ 2 }O+{ 2e }^{ - }$
$\therefore$   moles of ${ O } _{ 2 }$ released at anode $=\dfrac { 2t }{ 96500 } \times \dfrac { 1 }{ 4 } $

$\therefore$   $\dfrac { 2t }{ 96500 } \times \dfrac { 1 }{ 4 } =0.5$
$\Rightarrow t=96500$ secs $=26.8$ hours

$\therefore$   The time required for formation of $0.5$ mole of ${ O } _{ 2 }$ is $26.8$ hours.

Hence, the correct option is A.
Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

A current being passed for two hour through a solution of an acid liberating 11.2 litre of oxygen at NTP at anode. What will be the amount of copper deposited at the cathode by the same current when passed through a solution of copper sulphate for the same time?

  1. 16 g

  2. 63 g

  3. 31.5 g

  4. 8 g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) $63 \; g$

At STP,
$1$ mole of oxygen gas $= 32 \; g = 22.4 \; L$
Therefore,
$11.2 \; L$ of ${O} _{2} = \cfrac{32}{22.4} \times 11.2 = 16 \; g$
Therefore,
$\cfrac{{M} _{Cu}}{{M} _{{O} _{2}}} = \cfrac{{E} _{Cu}}{{E} _{O}}$
$\Rightarrow \cfrac{{M} _{Cu}}{16} = \cfrac{\left( \cfrac{63}{2} \right)}{\left( \cfrac{16}{2} \right)}$
$\Rightarrow {M} _{Cu} = 63 \; g$
Hence the amount of copper deposited at the cathode is $63 \; g$.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

A current of 9.65 Ampere flowing for 10 minutes deposits 3 g of metal which is monovalent, the atomic mass of metal is a:

  1. 10

  2. 50

  3. 30

  4. 96.5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) $50$

Weight of metal deposited $= 3 \; g$
Quantity of electricity passed $\left( q \right)$-
$q = I \times t$
Given:-
$I = 9.65 A$
$t = 10 \; min = 10 \times 60 = 600 \; sec$
$\therefore q = 9.65 \times 600 = 5790 \; C$
Now, as we know that,
Eq. wt. of metal $= \cfrac{\text{Weight of metal}}{q} \times F$
$\Rightarrow$ Eq. wt. of metal $= \cfrac{3}{5790} \times 96500 = 50 \; g$
As the metal is monovalent, atomic weight of metal will be equal to its equivalent weight.
Therefore,
Atomic weight of metal $= 50 \; g$

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Which of the following ($1\ M$) conducts more electricity?

  1. Sulphuric acid

  2. Boric acid

  3. Nitric acid

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

Conductivity in solutions depends on the degree of dissociation. Sulfuric acid (H2SO4) is a strong acid and dissociates completely into ions, whereas boric and phosphorous acids are weak acids and dissociate poorly.