What are fuel cells? State Two advantages of hydrogen-oxygen fuel cell over ordinary cell.
Step 1: Definition of Fuel Cells: Fuel cells are electrochemical devices that convert chemical energy into electrical energy through a redox reaction between fuel (e.g., hydrogen) and an oxidizing agent (e.g., oxygen).
Step 2: Advantages of Hydrogen-Oxygen Fuel Cell: 1. Higher Efficiency: Fuel cells have higher efficiency compared to conventional electrochemical cells. 2. Eco-friendly: Produces only water as a byproduct, making it environmentally friendly.


Electricity is passed through an acidic solution of Cu$^{2+}$ till all the Cu$^{2+}$ was exhausted, leading to the deposition of 300 mg of Cu metal. However, a current of 600 mA was continued to pass through the same solution for another 28 minutes by keeping the total volume of the solution fixed at 200 mL. The total volume of oxygen evolved at STP during the entire process is ___ mL. (Nearest integer)
Given:
$\mathrm{Cu^{2+} + 2e^- \rightarrow Cu(s)}$
$\mathrm{O_2 + 4H^+ + 4e^- \rightarrow 2H_2O}$
Faraday constant = 96500 C mol$^{-1}$
Molar volume at STP = 22.4 L