Tag: electrochemistry, rechargeable batteries, and fuel cells

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Questions Related to electrochemistry, rechargeable batteries, and fuel cells

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

Which of the following is an example of simple fuel cell?

  1. Lead storage battery

  2. Leclanche cell
  3. $H _2 O _2$

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A fuel cell makes electricity using the energy released by mixing fuel with air, a reaction which creates water and sometimes also carbon dioxide. The most common fuel for fuel cells is hydrogen, which when reacted with oxygen from air produces only water.
$H _{ 2 }O _{2}$ is simple fuel cell which generates electricity by reduction of $H _{ 2 }$ & $O _{ 2 }$.   

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

Identify the reaction taking place at cathode in fuel cell.

  1. ${O} _{2}+2{H} _{2}O+4{e}^{-}\rightarrow 4{OH}^{-}$
  2. $2{H} _{2}+4{OH}^{-}\rightarrow 4{H} _{2}O+4{e}^{-}$
  3. ${O} _{2}+2{H} _{2}O+4{e}^{-}\rightarrow 4{OH}^{-}+{H}^{+}$
  4. $4{H} _{2}O+4{e}^{-}\rightarrow 2{H}^{2}+4{OH}^{-}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a fuel cell the hydrogen enters the fuel cell at the anode. A chemical reaction strips the hydrogen molecules of their electrons and the atoms become ionized to form $H^+$. The electrons travel through wires to provide a current to do work. The oxygen enters at the cathode, usually from the air. The oxygen picks up the electrons that have completed their circuit. The oxygen then combines with the ionized hydrogen atoms $(H^+)$, and water $(H _2O)$ is formed as the waste product which exits the fuel cell. 
Cathode side (a reduction reaction): $O _2 + 4H^+ + 4e^- \rightarrow 2H _2O$
or ${O} _{2}+2{H} _{2}O+4{e}^{-}\rightarrow 4{OH}^{-}$

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

Which of the following reactions is used to make a fuel cell?

  1. $Cd(s) + 2Ni(OH) _{3} (s) \rightarrow CdO(s) + 2Ni(OH) _{2} (s) + H _{2}O(l)$
  2. $Pb(s) + PbO _{2}(s) + 2H _{2} SO _{4}(aq) \rightarrow 2PbSO _{4}(s) + 2H _{2}O(l)$
  3. $2H _{2}(g) + O _{2}(g) \rightarrow 2H _{2}O(l)$
  4. $2Fe(s) + O _{2}(g) + 4H^{+} (aq) \rightarrow 2Fe^{2+}(aq) + 2H _{2}O(l)$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reaction used in fuel cell is
$2H _{2}(g) + O _{2}(g) \rightarrow 2H _{2}O (l)$

At anode: $[H _{2} \rightarrow 2H^{+} + 2e]\times 2$
At cathode: $O _{2} + 2H _{2}O + 4e\rightarrow 4OH^{-}$

Hence, option C is correct.

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

An examples of a simple fuel cell is:

  1. lead storage battery
  2. $H _{2} - O _{2}$ cell

  3. daniell cell

  4. lechlanche cell
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$\rightarrow$ The galvanic cells in which the energy of combustion of fuels is directly converted into electrical energy are called fuel cells.
$\rightarrow$ The common example of fuel cell is hydrogen-oxygen fuel cell. Fuel cells are different from ordinary galvanic cells.

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

Fuel cell involves which of the following reaction(s) ?

  1. $O _{2}(g) + 2H _{2}O(l) + 4e^{-} \rightarrow 4OH^{-}(aq.)$ (at cathode)
  2. $O _{2}(g) + 2H _{2}O(l) + 4e^{-}\rightarrow 4OH^{-}(aq.)$ (at anode)
  3. $2H _{2}(g) + 4OH^{-}(aq.) \rightarrow 4H _{2}O(l) + 4e^{-}$ (at anode)
  4. $2H _{2}(g) + 4OH^{-}(aq.) \rightarrow 4H _{2}O(l) + 4e^{-}$ (at cathode)
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

Question approach,

at anode- loss of electron takes place,
at cathode- gain of electron takes place,
in option B, at anode gain of electron is talking place and in option D at cathode, loss of elctron is taking place;
so, both these statements are wrong
option A and C are representing the Hydrogen fuel cell reactions
hence, both A and C are correct options. 

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

In _________ cells, reactants are continuously supplied energy which can be withdrawn indefinately until outside supply of reactant is maintained. These cells are more efficient than conventional batteries and moreover, these are eco-friendly. 

  1. fuel

  2. galvanic

  3. primary

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

Fuel cell is a device that generates electricity by chemical reaction. Every fuel cell has one positive and one negative electrode called anode and cathode respectively. The reactions that produce electricity take place at electrodes.

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

Which of the following statements regarding fuel cell is (are) true?

  1. They have efficiency of about 60-70%

  2. There efficiency is less then conventional methods

  3. They do not cause pollution

  4. They can supply indefinite amount of energy until outside supply of reactants is maintained
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

Fuel cells have efficiency of 60-70%. Reactants, products and catalyst used are non- toxic, thus, they are pollution-free. And they can supply indefinite amount of energy until outside supply of reactants like H$ _{2}$ and O$ _{2}$  is maintained.

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

In a $H _2 - O _2$ fuel cell, combustion of hydrogen occurs to:

  1. remove adsorbed oxygen from electrode surface

  2. create potential difference between the two electrodes

  3. produce high purity water

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

Combustion of hydrogen occur in ${ H } _{ 2 }-{ O } _{ 2 }$ fuel cell because of difference in potential between two electrode. So on one electrode oxidation occur while on another reduction.