Question

What has more enthalpy, 2 moles of hydrogen atoms or 1 mol of h2?

Answer 1

Two moles of hydrogen atoms have higher enthalpy than one mole of molecular hydrogen (H₂) because forming a molecular bond releases energy, thereby lowering the enthalpy of the system.

Step-by-step explanation:

The question of whether 2 moles of hydrogen atoms (2H(g)) or 1 mole of molecular hydrogen (H₂(g)) has more enthalpy can be explored through understanding the enthalpy change associated with the formation of molecular hydrogen from its atomic form. When 2 moles of hydrogen atoms combine to form 1 mole of molecular hydrogen (H₂), energy is released, which implies that the atomic form has higher enthalpy compared to the molecular form, since the process of bond formation releases energy and lowers the enthalpy of the system.

For example, consider the reaction where 2 mol H₂ react with 1 mol O₂ to produce 2 mol H₂O:

2H₂(g) + O₂(g) → 2H₂O(l)

This reaction results in the release of 286 kJ of heat per mole of water produced if liquid water is formed. This is a direct indicator of the exothermic nature of the reaction, wherein the formation of molecular hydrogen (and subsequently water) is associated with the release of energy as heat, reducing the overall enthalpy of the system.

Therefore, 2 moles of hydrogen atoms (2H(g)) have more enthalpy than 1 mole of molecular hydrogen (H2(g)).

Answer 2

The enthalpy change of 1 mole of H₂ is given as 286 kJ of heat released when it changes to 1 mole of H₂O. However, 2 moles of H do not have a specified enthalpy change.

The enthalpy change of a reaction depends on the physical states of the reactants and products. In this case, the enthalpy change of 1 mole of hydrogen gas (H₂) is given as 286 kJ of heat released when it changes to 1 mole of liquid water (H₂O). This is known as the enthalpy of formation. On the other hand, 2 moles of hydrogen atoms (2H) do not have a specified enthalpy change. Therefore, 1 mol of H₂ has more enthalpy compared to 2 mol of H.