Tag: chemistry

Questions Related to chemistry

Identify the reaction taking place at cathode in fuel cell.

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

  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. $4{H} _{2}O+4{e}^{-}\rightarrow 2{H}^{2}+4{OH}^{-}$

Show answer
Correct Option: A
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 ${O} _{2}+2{H} _{2}O+4{e}^{-}\rightarrow 4{OH}^{-}$

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

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

  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. $2Fe(s) + O _{2}(g) + 4H^{+} (aq) \rightarrow 2Fe^{2+}(aq) + 2H _{2}O(l)$

Show answer
Correct Option: C
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.

An examples of a simple fuel cell is:

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

  1. lead storage battery

  2. $H _{2} - O _{2}$ cell

  3. daniell cell

  4. lechlanche cell

Show answer
Correct Option: B
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.

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

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

  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)

Show answer
Correct Option: A,C
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. 

In a fuel cell the fuel is fed to which compartment?

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

  1. Anode compartment

  2. Cathode compartment

  3. Both the compartments

  4. None of the above

Show answer
Correct Option: A
Explanation:

Therefore, it can clearly be said that fuel is fed to the anode compartment.

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. 

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

  1. fuel

  2. galvanic

  3. primary

  4. secondary

Show answer
Correct Option: A
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.

In hydrogen fuel cell the catalyst used is/are:

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

  1. $Ag$

  2. $Fe$

  3. $Pt$

  4. $Zn$

Show answer
Correct Option: A,C
Explanation:

$Ag$ and $Pt$ being inert are used for catalyst in the fuel cell.

A and C are correct

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

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

  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

Show answer
Correct Option: A,C,D
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.

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

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

  1. remove adsorbed oxygen from electrode surface

  2. create potential difference between the two electrodes

  3. produce high purity water

  4. generate heat

Show answer
Correct Option: B
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.

The solid form of water is known as:

chemistry rain: where does it come from sources of water and water cycle availability and forms of water the water cycle

  1. fog

  2. dry ice

  3. ice

  4. snow

Show answer
Correct Option: C
Explanation:

The solid form of water is known as ice.