Chemistry · Physics

Electrochemistry and Current Electricity

224 Questions

Review fundamental concepts of electrochemistry and current electricity through these practice questions. The set includes numerical problems on electrolysis, drift velocity, and electrode potentials. These topics frequently appear in engineering, CSIR NET, and state PSC prelims examinations for thorough preparation.

Electrolysis calculationsElectrode potentialNernst equationDrift velocityFuel cellsMolar conductivity

Electrochemistry and Current Electricity Questions

Multiple choice physics electrical quantities electric potential and potential difference potential difference current in electric circuits

how many electrons should pass through a conductor in $1$ second to constitute 1 amp current, it the charge one Eatonton is $1.6\times{10}^{-19}$

  1. $6.25\times{10}^{18}$
  2. $6.9\times{10}^{18}$
  3. $6.5\times{10}^{19}$
  4. $6.25\times{10}^{15}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1 ampere means 1 coulomb of charge flows per second. Since each electron carries 1.6 × 10^-19 C, the number of electrons needed is 1 ÷ (1.6 × 10^-19) = 6.25 × 10^18. Option A correctly shows this calculation.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

An aluminium (Al) rod with area of cross-section $4\times 10^{-6}m^2$ has a current of 5A. Flowing through it. Find the drift velocity of electron in the rod. Density of $Al=2.7\times 10^3kgm^{-3}$ and atomic wt.=27. Assume that each Al atom provides one electron.

  1. $8.6\times 10^{-4}ms^{-1}$
  2. $6.2\times 10^{-4}ms^{-1}$
  3. $1.2\times 10^{-4}ms^{-1}$
  4. $3.8\times 10^{-3}ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Drift velocity v_d = I / (n*A*e). The number density n = (density * Avogadro's number) / atomic weight. Calculating n for Aluminum and substituting into the formula yields approximately 1.2*10^-4 m/s.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

The number of free electrons passing through the filament of an electric lamp is one hour when the current through the filament is 0.32 A will be 

  1. $3\times { 10 }^{ 22 }$
  2. $2\times { 10 }^{ 26 }$
  3. $7.2\times { 10 }^{ 19 }$
  4. $7.2\times { 10 }^{ 21 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total charge Q = I * t = 0.32 A * 3600 s = 1152 C. Number of electrons n = Q / e = 1152 / 1.6*10^-19 = 7.2*10^21.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

The number of electrons striking the screen of CR is $7.5\times 10^{15}$ in 10 s. Calculate the electric current

  1. $1.2\times10^{-4}$
  2. $7.5\times10^{-4}$
  3. $1.6\times10^{-4}$
  4. $1.2\times10^{-5}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Current I = q / t = (n * e) / t = (7.5*10^15 * 1.6*10^-19) / 10 = 1.2*10^-4 A.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

In electrolysis, mass of the substance liberated at cathode is proportional to 

  1. strength of the current passed.

  2. time of passage of current.

  3. quantity of electricity passed.

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

According to the first law of electrolysis the mass of of substance liberated at cathode is proportional to the quantity of electric charge passed through it or indirectly it's proportional to the quantity of  electricity  passed. 

$\because$ $m= k \times q$

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

$H^{+}$ ions are reduced at platinum electrode prior to__________.

  1. $Zn^{2+}$
  2. $Cu^{2+}$
  3. $Ag^{+}$
  4. $I _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$H^+$ ions are reduced at platinum electrode prior to $Zn^{2+}$.

Because reduction potential of $\underset {(aq.)}{Zn^{+2}}+2e^- \longrightarrow Zn (s)$  $(-0.76)$
It means that it favours for oxidation rather than reduction.
Where reduction potential of $\underset {(aq.)}{2H^+}+2e^- \longrightarrow H _2 (g)$         $ (0)$
                                                  $\underset {(aq.)}{Cu^{+2}}+2e^- \longrightarrow Cu (s)$     $(0.16)$
                                                  $\underset {(aq.)}{Ag^+}+e^- \longrightarrow Ag(s)$         $(0.22)$
                                                  $\underset {(s)}{I _2}+2e^- \longrightarrow \underset {(aq.)}{2I^-} $               $(0.54)$

Multiple choice physics static electricity explaining static electricity charging by induction electric charges and fields

The number of electrons that must be removed from an electrically neutral silver dollar to give it a charge of $+2.4C$ is

  1. $2.5\times { 10 }^{ 19 }$
  2. $1.5\times { 10 }^{ 19 }$
  3. $1.5\times { 10 }^{ -19 }$
  4. $2.5\times { 10 }^{ -19 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total charge, $q=+2.4C$
Then by quantization of charge $q=ne$
$\therefore$ number of electrons, $\quad n=\cfrac { q }{ e } =\cfrac { 2.4C }{ 1.6\times { 10 }^{ -19 } } =1.5\times { 10 }^{ 19 }\quad \quad $

Multiple choice biology absorption by roots - the processes involved manure manures and fertilisers water absorption organ

A root hair cell under ordinary conditions have a water potential in the range of?

  1. $-1$ to $-4$ atm.
  2. $-1$ to $+4$ atm.
  3. $1$ to $2$ atm.
  4. $-1$ to $2$ atm.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Under ordinary conditions, the water potential of a root hair cell is negative, typically ranging between -1 and -4 atm, which allows it to absorb water from the soil.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

When an electric current is passed through an aqueous solution of the following, the concentrations of cation as well as anion will not change for (assume constant volume of the electrolytic solution)

  1. $ C _{S} CI $
  2. $ KNO _{3}$
  3. $ AgNO _{3}$
  4. $ HCI$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

KNO3 is a strong electrolyte where both K+ and NO3- ions have high reduction/oxidation potentials compared to water. During electrolysis, water is preferentially electrolyzed, leaving the concentration of K+ and NO3- ions effectively unchanged.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

Electrolysis of a solution of $ MnSO _{4}$ in aqueous sulphuric acid is a method for the preparation of $ MnO _{2}$ as per the reaction: $ Mn^{2+}(aq)+2H _{2}O\rightarrow MnO _{2}(s)+2H^{+}(aq)+H _{2}(g).$ Passing a current of 19.3 A for 2 h gives only 52.2 g of $MNO _{2}.$ The current efficiency is (Mn = 55)

  1. 8.33 %

  2. 83.33 %

  3. 41.67 %

  4. 100 %
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Calculate theoretical yield using Faraday's laws: Q = I * t = 19.3 * 7200 = 138960 C. Moles of electrons = Q / F = 138960 / 96500 = 1.44 mol. Reaction: Mn2+ + 2H2O -> MnO2 + 4H+ + 2e-. Moles of MnO2 = 1.44 / 2 = 0.72 mol. Mass = 0.72 * 87 = 62.64 g. Efficiency = (52.2 / 62.64) * 100 = 83.33%.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

If mercury is used as cathode in the electrolysis of aqueous NaCl solution, the ions discharged at cathode are:

  1. H$^+$
  2. Na$^+$
  3. OH$^-$
  4. Cl$^-$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In presence of Hg electrode, sodium ions are discharged in the form of a mercury sodium amalgam and chloride ions are converted to chlorine. 
So, $Na^+$ ions discharged at cathode.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

State True or False.
The ratio of gases liberated at cathode and anode during electrolysis of CH$ _3$COONa(aq) is 1 : 3.

  1. True

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

The given statement is True.
 The ratio of gases liberated at cathode and anode during electrolysis of $\displaystyle CH _3COONa$ (aq) is $\displaystyle 1:3$
$\displaystyle 2CH _3COONa \rightarrow CH _3-CH _3 \uparrow + 2CO _2  \uparrow+2NaOH+H _2 \uparrow$
hydrogen gas is liberated at cathode and ethane and carbon dioxide gases are liberated at anode.