Exam Q 5

Question 1

Determine the type of bonding arsine (AsH3) is expected to have

Answer 1

It will have covalent bonding as As has a valency of 5 electrons and H has a valency of 1 electron, As then requiring 3 hydrogens to complete its outer shell and the 3 hydrogens requiring 1 electron each to share from As.

In terms of polar and non-polar:
The elements have an electronegativity difference of 0 making the molecule non-polar but as seen in its original shape, it becomes polar due to the lone pairs

Question 2

Which of the three hydrides (NH3, PH3, AsH3) would you expect to have intermolecular hydrogen bonding?

Answer 2

NH3 as Nitrogen is small and strongly electronegative and hydrogen bonds occur when hydrogen is bonded to nitrogen

Question 3

Suggest a reason why ammonia (NH3) has the highest boiling points of the three hydrides

Answer 3

hydrogen bonding in ammonia is stronger than the other intermolecular forces