Question

In terms of the least polluting source of energy, _________ is an ideal source of energy.

• A. Hydrogen
• B. Coal
• C. Crude oil
• D. None of these

Answer 1

The correct option is A Hydrogen

Hydrogen fuel is a zero-emission fuel when burned with oxygen. In a flame of pure hydrogen gas, burning in air, hydrogen $\left(H_2\right)$ reacts with oxygen $\left(O_2\right)$ to form water $\left(H_{2}O\right)$ and releases energy.
$2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(g\right)$
It is often used in internal engines, to power vehicles and electric devices. It is also used in the propulsion of spacecraft and might potentially be mass-produced and commercialized for passenger vehicles and aircraft. The only limitation with using Hydrogen fuel is; Since hydrogen gas is so light, it rises in the atmosphere and is therefore rarely found in its pure form i.e. $H_2$.