C6.4 Hydrogen Bonding

Question 1

what is the definitin of a hydrogen bond?

Answer 1

special type of permanent-dipole -dipole ineractin found between certain molecules

Question 2

what molecules can have hydrogen bonds?

Answer 2

• an elecronegative atom with lone pair electrons, (o2, f2, n2)
• hydrogen atom attached to an electronegative atom (h-f, h-n, h-0)

acts between lone pair of electronegative atom in one molecule, and hydr

Question 3

anomalous properties of water

Answer 3

hydrogen bonds have the most significant influence on water, support existence of life on earth

Question 4

anomalous water properties : density

Answer 4

ice less dense
hydrogen bonds hold water molecules apart in open lattice structure (open tetragedral lattice structure with holes, decreasing density)
water molecules in ice further apart than water
solid ice less dense than liquid water ; floats

Question 5

anomalous water properties: mp and bp

Answer 5

high mp and bp
- hydrogen bonds are strongest intermolecular forces, stronger than london forces
- high amount of energy needed to overcome these bonds, water has much higher mp and bp
- ice lattice breaks, rigid arrangement of hydrogen bonds in ice = broken
- water boils, hydrogen bonds completely break

Question 6

water properties: surface tension

Answer 6

• cohesive properties of water, letting insects walk on water, forms film on water
• also used to bond bases in DNA