Calorific value of Hydrogen is:

Question

Accepted Answer

The correct option is (3):

The calorific value of a fuel is defined as the total amount of heat energy produced when a unit mass (or volume) of the fuel is completely combusted. Hydrogen is well-known for having the highest calorific value among all common fuels. This makes it an incredibly efficient and clean fuel, producing only water vapor upon combustion, as shown by the reaction: $\mathrm{2H_2(g) + O_2(g) \rightarrow 2H_2O(l) + Energy}$. The standard calorific value of hydrogen (specifically, its higher heating value, which includes the latent heat of vaporization of water formed) is approximately $1,50,000 \mathrm{~kJ/kg}$. This exceptionally high value is why hydrogen is often considered a futuristic fuel, particularly for applications requiring high energy density and minimal environmental impact, such as rocket propulsion and fuel cells. Understanding this value is crucial for comparing different fuels and assessing their energy efficiency.

The incorrect option is (1): $1500 \mathrm{~kJ/kg}$ is significantly lower than the actual calorific value of hydrogen, indicating a considerable underestimation of its energy content. This value might be confused with fuels having much lower energy density.

The incorrect option is (2): $150 \mathrm{~kJ/kg}$ is an extremely low value for the calorific value of hydrogen. Such a low figure would make hydrogen an impractical fuel source, which contradicts its known properties as a high-energy fuel.

The incorrect option is (4): $15000 \mathrm{~kJ/kg}$ is also lower than the actual calorific value of hydrogen. While it is a substantial amount of energy, it still falls short of hydrogen's true energy density, which is approximately ten times higher.