2.26 - Intermolecular Interactions and Physical Properties Flashcards
What is the trend in boiling point for alkanes as you increase the carbon chain length?
It increases
What are the only type of intermolecular forces for alkanes?
London Forces
Why does boiling point increase with chain length for alkanes?
Because there are more London forces, so more energy is needed to overcome them
Do branch-chain alkanes have higher or lower boiling points than straight-chain alkanes?
Lower
Why?
Because there are fewer points of contact, so less intermolecular forces
What other type of intermolecular force can alcohols form?
Hydrogen bonds
Why?
Because they contain an -OH group
What is the trend in boiling points for the hydrogen halides?
Steady increase from HCl to HI
Why?
Increased electrons lead to increased London Forces
What are the two anomalous properties of water?
- Relatively high melting and boiling temperature for a molecule with so few electrons
- The density of ice is less than the density of water (at 0 degrees)
Why does water have a relatively high boiling point?
Hydrogen bonding between molecules
How many hydrogen bonds does water form per molecule?
2
What are the two conditions for dissolving?
- Solute particles must be separated from each other
- Forces of attraction between solute and solvent paeticles musty be greater than those between solute and solute
Why do most ionic solids dissolve in water?
Because the energy required to separate the ions is provided by hydration
