Tag: chemical reactions

Questions Related to chemical reactions

Arrange the following complexes in order of increasing electrical conductivity.
(I) $[CoCl _3(NH _3) _3]$     (II) $[CoCl(NH _3) _5]CI _2$
(III) $[Co(NH _3) _6]Cl _3$   (IV) $[CoCl _2(NH _3) _]1Cl$ 

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. III > II > IV > I

  2. II > III > IV > I

  3. II > III > I > IV

  4. III > IV > II > I

Show answer
Correct Option: A
Explanation:

Electrical conductivity $\times $ no. / moles of ions present after dissociation.

$I$ $\therefore \quad \left[ Co{ Cl } _{ 3 }{ \left( { NH } _{ 3 } \right)  } _{ 3 } \right] $
$II$  $\left[ CoCl{ \left( { NH } _{ 3 } \right)  } _{ 5 } \right] { Cl } _{ 2 }\rightarrow { \left[ CoCl{ \left( { NH } _{ 3 } \right)  } _{ 5 } \right]  }^{ 2+ }+2{ Cl }^{ \left( - \right)  }$
$IV$  $\left[ Co{ Cl } _{ 2 }{ \left( { NH } _{ 3 } \right)  } _{ 4 } \right] Cl\rightarrow { \left[ Co{ Cl } _{ 2 }{ \left( { NH } _{ 3 } \right)  } _{ 4 } \right]  }^{ + }+{ Cl }^{ \left( - \right)  }$
$III$  ${ \left[ Co{ \left( { NH } _{ 3 } \right)  } _{ 6 } \right] Cl } _{ 3 }\rightarrow { \left[ Co{ \left( { NH } _{ 3 } \right)  } _{ 6 } \right]  }^{ 3+ }+3{ Cl }^{ \left( - \right)  }$
Hence the correct answer is,
$\boxed { III>II>IV>I } $

The electric conduction of a salt solution in water depends on the:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. shape of molecules

  2. size of its molecules

  3. size of solvent molecules

  4. extent of its ionisation

Show answer
Correct Option: D
Explanation:

Higher the number of ions in solution, higher would be the conductivity of the solution as the number of charge carriers would increase. Hence, higher the degree of ionization greater would be the number of ions in solution.

Kim Istry was tired and thirsty after her soccer game, so she drank a sports drink that contained electrolytes. Kim is smart girl who known that when electrolytes dissolve in water, they produce solutions that can conduct an electric current. She also knows that the type of bonding in a substance can determined whether or not it is an electrolyte.
Which of the following substances is classified as an electrolyte?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. Sodium chloride, $NaCl$

  2. Glucose, $C _{6}H _{12}O _{6}$

  3. Water, $H _{2}O$

  4. Ethanol, $C _{2}H _{5}OH$

Show answer
Correct Option: A
Explanation:

The electrolyte present in sports drink is sodium chloride.

Conductivity of aqueous solution of an electrolyte depends on:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. molecular mass of the electrolyte

  2. boiling point of solvent

  3. degree of ionisation

  4. volume of the solvent

Show answer
Correct Option: C
Explanation:

Conductivity of an aqueous solution depends on degree of ionization of solute. More is the degree of ionization more will be conductivity. Second, important factor on which conductivity depend is temperature.

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

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. photoelectric cells

  2. semiconductors

  3. high voltage batteries

  4. lasers

Show answer
Correct Option: A
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.

Pure water is a good conductor of electricity.

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. True

  2. False

Show answer
Correct Option: B
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)

Molten sodium chloride conducts electricity due to presence of:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. free electrons

  2. free ions

  3. free molecules

  4. free atoms

Show answer
Correct Option: B
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.

Metallic conduction depends upon which of the following?

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. The nature of the metal

  2. Number of valence electrons per atom

  3. Density of metal

  4. Temperature

Show answer
Correct Option: A
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.

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

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. 26.805 h

  2. 153.61 h

  3. 107.22 h

  4. None of these

Show answer
Correct Option: D
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.

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:

metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

  1. 26.8 hours

  2. 13.4 hours

  3. 6.7 hours

  4. 28.6 hours

Show answer
Correct Option: A
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.