Lecture 2 Flashcards
In terms of electron configuration, how would you describe water?
sp3 hybridised.
What type of bonds do the hydrogens form with the oxygens in water?
Single polar covalent bonds.
What is electronegativity?
The tendency of an atom to attract electrons.
Why is the bond angle of water not 109.5º?
And what is it instead?
Lone pairs repel each other more than bonding pairs, reducing the bond angle.
104.5º.
Why do water molecules stick together more than other molecules?
Hydrogen bonds.
What 9 effects does hydrogen bonding have on the properties of H2O?
Higher bpt, Higher cohesion, Higher heat of vaporisation, Ice has a more open structure than water (FLOATS). Higher surface tension, Higher specific heat, Good solvent for polar molecules. God solvent for ionic compounds. Oil-drop effect.
Average number of hydrogen bonds per ice and water molecule?
Ice = 4 H-bonds per molecule. Water = 3.7 H-bonds per molecule.
What is specific heat capacity?
The amount of heat absorbed or lost to alter temperature of 1g of water by 1ºC.
What is a real-life example of a use of cohesion tension?
One molecule of water dragging another up a tree.
What is the heat of vaporisation?
Energy to convert 1g of water from liquid to gas at 25ºC.
What effect does heat and cold have on H bonds?
Heat - breaks H bonds (uses heat).
Cold - makes H bonds (produces heat).
What is the oil drop effect?
Clustering of non-polar molecules in water.
Why does the oil drop effect occur?
To maximise number of H-bonds which can be formed in water, making H2O molecules more stable.
What is molecular mass?
Sum of masses of all atoms in a molecule.
What is avogadro’s number?
6.02X10^23 molecules.
When water dissociates, what does it form?
Hydronium ion (H30+), Hydroxide ion (OH-).
What is Kw?
[H+][OH-].
Is Kw a universal constant? If so, under what conditions?
Yes, under standard temperature and pressure.
What is pH equation?
-log10[H+].
