Chapter 2 Water Flashcards
How much of our body is made of water?
2/3 full
Reactivity of functional groups depends on __
pH
Order of bonding interactions
Covalent, ionic, hydrogen, dipole-dipole interactions, London dispersion
what is hydrogen’s bond strength?
20
What molecules are used for hydrogen bonding?
N, O, F, S, Cl
Structure of Ice
hexagonally packed (honeycomb shaped) that fully satisfies the H-bonding potential of H2O molecules
How many H molecules are in H2O ice?
4 with tetrahedral shape
Water is most dense at ___
4 degrees celsius
Liquid water is ___ than ice
denser
Water is one of the most ___ solvents around
polar
What is water good for dissolving?
charged and polar species
Why does water/oil not mix?
oil is less dense than water, the non polar and polar do not mix
What happens when a small amount of a nonpolar solute gets immersed in water?
Water molecules organize in an H-bond network around the non polar solute to accommodate it
Does entropy increase or decrease if water is added to nonpolar solvent?
At first, it decreases because it has to become orderly. It will soon disperse and increase as it tries to get out of the situation
What are clathrates?
Molecules in the cage-like structure on the deep ocean floor
Hydrophobic interactions
Entropically driven by the overall increase in entropy that water molecules achieve by excluding a non-polar solute
What are amphiphilic molecules?
molecules that can be both polar and nonpolar
What is an example of amphiphilic molecules?
fatty acids, soap or SDS (detergent)
What is a micelle formation?
When water molecules refuse the hydrophobic tails. The H2O molecules become highly ordered. Only lipid portions at the edge can force ordering water causing increase in entropy. All the hydrophobic groups are sequestered from water and a shell of H2O molecules is minimized.
What is a monolayer?
One or two tailed detergents in low concentrations form
What is a micelle?
one tailed amphiphiles in higher concentrations
What is a bilayer vesicle?
two tailed amphiphiles in higher concentrations
Osmosis
movement of water from a region of high water concentration to a low water concentration (depends on solute concentration)
pH = pKa when [A] = ? and what is this called?
[HA], inflection point
What is one of the most important buffers?
phosphoric acid (h2po4-)
When do buffers occur?
when weak acid and its conjugate base are present in nearly equal proportions
When is the buffer the best?
when pH = pKa
Hyperventilation
- expels too much CO2 and not enough acid
- blood pH goes up (respiratory alkalosis)
(breathe in brown paper bag)
What is the normal pH for our blood?
7.4
CO2 is exhaled from lungs and ….
The breathing rate (lungs) control CO2 concentration and kidneys control HCO3- concentration
What antiacid calls blood pH to go up?
bicarbonate acid
What happens at blood pH 7.3?
discomfort, headache (ACIDOSIS)
What happens at blood pH 7.1?
coma
What happens at blood pH 6.9?
death
Molecular structure of water
tetrahedral when considering lone pairs but bent without lone pairs
Structure of liquid water
- Only 15% less H-bonded than ice
- An average of 3.4 H-bonds per h2o molecules
- Transitory in nature
- Reorient every 10-12 seconds
- Short term h2o interactions are tetrahedral in nature
Hypertonic
water moves out and cells shrink (high solute conc)
Hypotonic
water moves in, creating outward pressure, cell swells and may eventually burst (low solute conc)
concentration of p(x) =
-log (x)
what does weak electrolyte mean?
doesn’t fully dissociate
the lower the pKa…..
the stronger the acid
