A1 - Intermolecular Forces Flashcards
Which substances have intermolecular forces between molecules?
Simple molecules
Are intermolecular forces strong or weak?
Weak
What are the three types of intermolecular forces?
Hydrogen bonding, Permanent dipole-dipole, Induced dipole-dipole
Which is the strongest type of intermolecular force?
Hydrogen bonding
Which is the weakest type of intermolecular force?
Induced dipole-dipole
What is a non-polar molecule?
A non-polar molecule has electrons distributed evenly throughout the molecule.
What is a polar molecule?
A polar molecule has an uneven electron distribution, with a partial positive charge on one part of the molecule and a partial negative on another part.
When substances with a simple molecular structure are melted or boiled what is broken?
Weak intermolecular forces are broken
Do simple molecules have a high melting point or a low melting point?
Low. The weak intermolecular forces between molecules are broken.
What is the strongest intermolecular force between polar molecules?
Permanent dipole-dipole
What is the strongest intermolecular force between non-polar molecules?
Induced dipole-dipole
What is the strongest type of intermolecular force between simple molecules that have a H bonded to an N, O or F?
Hydrogen bonding
How do you know if simple molecules have hydrogen bonding between them?
- They have a H bonded to an N, O or F.
- A lone pair of electrons on the fluorine, oxygen or nitrogen
Hydrogen bonding is the strongest type of intermolecular force, true or false?
True
Induced dipole-dipole is the weakest type of intermolecular force, true or false?
True
Explain how is an induced dipole-dipole intermolecular force is formed between 2 non-polar molecules.
- Fluctuation in electron density
- Creates a temporary dipole in one molecule
- This induces a dipole in a neighbouring molecule
If the strongest intermolecular force between molecules is Hydrogen bonding, which other intermolecular forces do they also have?
Permanent dipole-dipole and Induced dipole-dipole
If the strongest intermolecular force between molecule is permanent dipole-dipole, which other intermolecular force do they also have?
Induced dipole-dipole
Non-polar molecules only have induced dipole-dipole forces between molecules, true or false?
True
What increases the strength of induced dipole-dipole forces?
More electrons
More surface contact area
Which has stronger induced dipole-dipole, Cl2 or Br2 ?
Br2. It has more electrons
Which has stronger induced dipole-dipole, F2 or I2 ?
I2. It has more electrons
Which has stronger induced dipole-dipole, S8 or P4 ?
P4. Bigger molecules so has more electrons
Which has stronger induced dipole-dipole, C3H8 or C4H10?
C4H10. Bigger molecules so has more electrons
Which has a higher boiling point, Cl2 or Br2 ?
Br2. It has more electrons so stronger induced dipole-dipole.
Which has a higher boiling point, F2 or I2 ?
I2. It has more electrons so stronger induced dipole-dipole.
Is CCl4 polar or non-polar molecule? (Clue: Draw it out with partial charges. Do they cancel out?)
Non-polar
Partial charges cancel out
Is CHCl3 polar or non-polar molecule? (Clue: Draw it out with partial charges.
Do they cancel out?)
Polar
Partial charges do not cancel out
Why does HBr have a higher boiling point than HCl? (Clue: is it polar or non-polar? What are all the types of intermolecular force it will have?)
Both polar molecules
Strongest intermolecular force is permanent dipole-dipole.
It will also have induced dipole-dipole.
HBr has more electrons that HCl, stronger induced dipole-dipole attraction.
Why does HI have a higher boiling point than HCl? (Clue: is it polar or non-polar? What other intermolecular force will it also have?)
Both polar molecules
Strongest intermolecular force is Permanent dipole-dipole.
It will also have induced dipole-dipole.
HI has more electrons that HCl, stronger induced dipole-dipole attraction.
Why does HI have a higher boiling point than HF? (Clue: is it polar or non-polar? What other intermolecular force will it also have?)
Both polar molecules
Strongest intermolecular force is Permanent dipole-dipole.
It will also have induced dipole-dipole.
HI has more electrons that HF, stronger induced dipole-dipole attraction.
