Hydrogen Bonding

Question 1

Examples of hydrogen bonding

Answer 1

Water + ammonia

Question 2

The bond is so POLARISED + and hydrogen has such a HIGH CHARGE DENSITY that…

Answer 2

The hydrogen atoms form weak bonds with LONE PAIRS OF ELECTRONS on the F, N or O of other molecules

Question 3

ORGANIC molecules forming H bonds often have…

Answer 3

• OH or -NH groups

e. g. alcohols + amines

Question 4

Using H bonds, explain why ice is less dense than water?

Answer 4

• ice - mol. arranged for max no. H bonds -> lattice structure “WASTES” space
• ice melts - H bonds break -> lattice breaks down = mol. fill space

Question 5

Substances with H bonds have high/low MP+ BP??

Answer 5

HIGH

lots energy to overcome IMB

Question 6

Which hydrides have highest boiling points?

Answer 6

Nitrogen , oxygen + fluorine

Question 7

Are substances with H bonds SOLUBLE?

Answer 7

Yes

Can form H bonds with water mol. –> mix + dissolve

Question 8

How does branched molecules affect the boiling point?

Answer 8

• less branched = greater surface contact
• mol. pack closer = stronger instantaneous-induced bonds

= higher BP

Question 9

How can measuring rate of evaporation show the strengths of different intermolecular bonds?

Answer 9

Weaker the IMB - the faster its rate of evaporation

= greater change in temp in 5 minutes
evaporation = endothermic

Question 10

Hydrogen bonding only occurs when…

Answer 10

Hydrogen is covalently bonded to

FLUORINE, NITROGEN, or OXYGEN

Question 11

what is a hydride?

Answer 11

a binary compound of HYDROGEN with a METAL