Which of the following statements are correct regarding a fuel cell that uses hydrogen and oxygen as fuels?
$A$. It has been used in spaceships.
$B$. It has an efficiency of about $40 \%$ to $60 \%$ to produce electricity.
$C$. It uses aluminium as a catalyst.
$D$. It is eco-friendly.
$E$. It is actually a type of galvanic cell.

In a fuel cell,$H_2$ and $O_2$ react to produce electricity. In this process,$H_2$ gas is oxidized at the anode and $O_2$ gas is reduced at the cathode. If $67.2 \ L$ of $H_2$ gas at $\text{STP}$ is consumed in $15 \ min$,what is the current produced (in $A$)?

Which of the following reactions is possible at the anode?

Consider the figure and answer the questions $(i)$ to $(vi)$ given below.
$(i)$ Redraw the diagram to show the direction of electron flow.
$(ii)$ Is the silver plate the anode or cathode?
$(iii)$ What will happen if the salt bridge is removed?
$(iv)$ When will the cell stop functioning?
$(v)$ How will the concentration of $Zn^{2+}$ ions and $Ag^{+}$ ions be affected when the cell functions?
$(vi)$ How will the concentration of $Zn^{2+}$ ions and $Ag^{+}$ ions be affected after the cell becomes 'dead'?

When a lead storage battery is charged:

What is a secondary cell? Give examples of it.