Question

10. (8 pts) Oxygen, sulfur and selenium are in the same column of the periodic table. One sitting under each other in the order listed. All reaction with two hydrogen atoms to form a stable compound H2Se has a higher boiling point than H2S. It is also heavier. Explain how this does (or doesn't) make sense. What explains the fact that water, H O, has a higher boiling point than hydrogen sulfide, H2S, which is heavier

Answer 1

solution:

1.

in periodic table Selenium is below sulfur, therefore, Se is a bigger atom than S, so it has got one extra electron shell. This means H2Se is a bigger molecule than H2S which suggested that the Van Der Waal forces on H2Se is stronger than on H2S which implies the energy required to to break the intermolecular forces for H2Se than H2S- this leads to H2S having the lower boiling point.

2.

In periodic table Selenium is below sulfur, therefore, Se is a bigger atom than S, so it has got one extra electron shell. This means H2Se is a bigger molecule than H2S which suggested that the Van Der Waal forces on H2Se is stronger than on H2S which implies the energy required to to break the intermolecular forces for H2Se than H2S- this leads to H2S having the lower boiling point. H2O forms intermolecular H bonding as below H2S forms intermolecular H bonding as below: In H2O and H2S, Oxygen and sulphur are the central atoms respectively. Among Oxygen and sulphur, Oxygen is more electronegative (tendency to gain electrons) and hence it can form more number of intermolecular H bonding with other water molecules than sulphur in H2S. More the number of H bondings, more will be the boiling point as its area increases which increases the Van Der Waals force of attraction. So, due to more electronegativity of oxygen in