if 3 moles of H2 react with two moles of o2 what is limiting reactant

H₂ is the limiting reactant.

Explanation:

H₂  reacts with O₂

The reaction would be

2H₂ + O₂ → 2H₂O

According to the balanced equation, 2 moles of H₂ reacts with 1 mole of O₂ to form 2 moles of H₂O.

The ratio of usage of H₂ and O₂ is 2 : 1 respectively

If 3 moles of H₂ and 2 moles of O₂ are present then:

3 moles of H₂ would require 1.5 moles of O₂                 ( 2 : 1 of H₂ and O₂ )

Out of 2 moles of O₂, 1.5 moles would be used and 0.5 mole would be in excess.

Therefore, H₂ is the limiting reactant as the number of moles of H₂ are not enough to use all the O₂.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.