A mixture of 5L of H2 and 3L O2 reacts to form H2O (g) at constant T and P .Find the volume of H2O gas obtained. 2H2 (g) + O2(g)
2H2O(g)

The  volume of H₂O = 5 L

Given

5L of H₂ and 3L O₂

Reaction

2H₂ (g) + O₂(g)  ⇒2H₂O(g)

Required

The  volume of H₂O

Solution

Avogadro's hypothesis:  

In the same T,P and V, the gas contains the same number of molecules  

So the ratio of gas volume will be equal to the ratio of gas moles  

mol H₂ = 5, mol O₂ = 3

From equation, mol ratio H₂ : O₂ = 2 : 1, so :

mol H₂O based on mol H₂, and from equation mol ratio H₂ : H₂O=2 : 2, so mol H₂O = 5 mol and the volume also 5 L

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explanation:

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.