Forces

Question 1

What affects Electronegativity

Answer 1

Nuclear charge:

• More protons more nuclear attraction to outer e
• Increases nuclear charge, increase electronegativity

Atomic radius:
• e closer to nucleus more strongly attracted to + nucleus
• Bigger radius, decrease electronegativity

Shielding:
• More shells, outer e have less attraction to nucleus
• more shielding, less electronegative

Question 2

Three intermolecular forces

Answer 2

1. Van der Waals: electron charge cloud moves —> non polar
2. Permanent dipole diplole: delta + end in one molecule attracted to delta - end —> polar
3. Hydrogen: When H covalently bond to F, O, N it’s highly polarised. H becomes so delta + it bonds with lone pair of F, O, N
   Type of permanent dipole dipole

•Hydrogen bond strongest
•Permanant stronger than van der Waal

Question 3

Surface tension in water

Answer 3

Ability of liquid to resist external forces
Hydrogen bonding in the molecules pull surface molecules downwards
Which makes it compressed and more tight at surface
Increasing surface tension

Question 4

Importance of hydrogen bonding in low density ice

Answer 4

Solids denser than liquids as particles more closely packed together
Hydrogen bond length shorter in solid

Question 5

Intermolecular forces in hydrocarbon

Answer 5

Only van der Waals

Question 6

Explain why ammonia molecules can exhibit hydrogen bonding

Answer 6

• Ammonia has N-H bond
• Delta + H atom forms hydrogen bond with lone pair on N of another ammonia NH3 molecule

Question 7

Explain why propanone, C3H6O, has a higher no than butane, C4H10, even though it has the same mr

Answer 7

• Propanone has C to O double bond
• Which is polar
• O is more e negative than C so there’s a permanent dipole
•Butane only has weaker van der Waals forces

Question 8

Why is CH3Br polar

Answer 8

• C—Br bind is polar
• Br more e negative than C
• the charge on the molecule is not symmetrical