Step 1: Understand what a fuel cell is.
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel directly into electrical energy. In the hydrogen-oxygen fuel cell, hydrogen acts as fuel and oxygen acts as oxidizing agent. The overall reaction produces water.
Step 2: Identify the characteristics of fuel cells.
Fuel cells are known for high efficiency because they convert chemical energy directly into electrical energy without combustion. In the hydrogen-oxygen fuel cell, the reaction is:
\[
\mathrm{2H_2 + O_2 \rightarrow 2H_2O}
\]
Because the main product is water, such cells are considered environmentally clean or nearly pollution free.
Step 3: Analyze the options.
(A) True. Fuel cells convert chemical energy directly into electrical energy.
(B) Not true. The water formed in hydrogen-oxygen fuel cells is generally considered pure enough and has even been used for drinking in space applications after proper handling.
(C) True. Hydrogen reacts with oxygen to form water in the fuel cell.
(D) True. Fuel cells are considered pollution free because they mainly produce water.
Step 4: Conclusion.
Hence, the statement which is not true for a fuel cell is that the water produced during the reaction cannot be used for drinking.
Final Answer:Water produced during reaction, can not be used for drinking.