Question

In which one pair does the first species have a higher boiling point than the second?

*** For any one pair, give your reasoning as to which species has the higher boiling point.

A) NH3 and N2

B) SO2(g) and S8(s)

C) HCl and LiF

D) CH4 and CBr4

E) C3H8 and C3H7OH

***The answer is A. NH3 and N2 but PLEASE show your work on you get that THANK YOU!!

Answer 1

NH3 has Hydrogena attached to more elctronegative atom N.   Hydorgen bonding is possible between Nh3 moleucles. Thus stronger attraction forces between NH3 molecules makes boiling point higher ( since more temperature is required to break those intermolecular forces) . N2 molecules have weak intermoclular forces .

Hence NH3 has higher BP compared to N2 becuase of stronger intermolecular forces between NH3 moelcules.

B) S8 is solid and hence its Boiling point is higher than SO2 gas.

c) HCl is polar covalent substance but LiF is ionic solid . Hence LiF has stronger BP

D) CBr4 has higher molar mass compraed to CH4. Higher molar mass substances have higher boiling point in general.

E) C3H7OH has Hydrogen attached to more electronegative O. Hence hydrogen bonding is intermocular forces between C3H7OH , C3H8 is non polar substance and hence weak dispersion forces are intermolecular forces betwene C3H8. Hence C3H7OH has higher BP since it has stronger intermoclular forces compared to C3H8.