Properties of water (Dr.Miles TAMU)

Question 1

What type of geometry is water and what other properties does it have?

Answer 1

• Tetrahedral and is SP^3 hybridized
• bent
• gives dipole moments

Question 2

Mutual reinforcement

Answer 2

The formation of the first hydrogen bond facilitates the second which upon forming facilitates forming the third which facilitates making the fourth. Thus the formation of hydrogen bonds is cooperative.

Question 3

What makes ice have a low density

Answer 3

Each water molecule acts as a donor for two H-bonds and as acceptors for two more. This causes an open structure

Question 4

Why are ionic salts soluble in water

Answer 4

Dipoles of water interact with cations and anions causing these ions to be hydrated which means surrounded by water molecules in hydration shells

Question 5

What charges can water solvate and how do the lone pairs do this?

Answer 5

both positive and negative
-Water orients its lone pairs of electrons towards positive charges and orients the partially positive hydrogens at negative charges (greater charge greater solubility)

Question 6

Water is an excellent solvent for

Answer 6

-Polar molecules (through hydrogen bonding)
-Ionic salts

Question 7

compounds with _____(7) are soluble in water

Answer 7

-hydroxyl group
- amines
- sulfhydryls
- carboxylates
-esters
- ketones
- amides

Question 8

Clathrate structure

Answer 8

When hydrophobic molecules dissolve into solution, water molecules form an ice like hydrogen bonding lattice
- causes a decrease in the entropy thus creating low solubility

Question 9

Amphiphiles

Answer 9

hydrophilic part and a hydrophobic part such as fatty acids and detergents. They have polar heads such as a carboxylate or phosphate group and a hydrophobic tail of hydrocarbons. The hydrophobic tails are caged in clathrate structures.

Question 10

Micelle formation

Answer 10

hydrophobic alkyl chains are sequestered in the inside of the micelle.
- this frees ordered water molecules thus increasing entropy

Question 11

hydrophobic interactions

Answer 11

forces that hold the nonpolar regions of the molecules together out of the aqueous solvent
- entropy driven
- drive globular protein folding, DNA double helix formation and membrane formation

Question 12

Colligative properties of aqueous solutions: Dissolved solutes….

Answer 12

• alter the physical properties of water
• lower the freezing point of water
• raise the boiling point of water
• impose local order of the water molecules surrounding them (difficult to arrange themselves in crystalline lattice or escape)

Question 13

How do dissolved solutes alter colligative properties of aqueous solutions

Answer 13

lower the effective concentration of water

Question 14

osmosis

Answer 14

Water molecules moving spontaneously from a region of high concentration to the region of low concentration

Question 15

biological membranes are _____ to water but _____ to ions and large polar molecules

Answer 15

permeable, impermeable

Question 16

isotonic

Answer 16

Solutions separated by a semipermeable membrane that are of equal molar concentration of solute
- no net movement of water across the membrane

Question 17

hypertonic

Answer 17

solution surrounding the semipermeable membrane has a higher molar concentration of solute than the solution inside of the membrane
- Water will rush out of the cell

Question 18

hypotonic

Answer 18

If the solution surrounding the semipermeable membrane has a lower molar concentration of solute than the solution inside of the membrane
- water will rush into the cell creating outward pressure causing the cell to swell and burst

Question 19

how do Bacteria and plants prevent osmosis catastrophes

Answer 19

Rigid cell walls of sufficient rigidity to resist osmotic pressure and prevent osmotic lysi

Question 20

how do Protozoa’s prevent osmosis catastrophes

Answer 20

a vacuole that pumps water continually out of the cell

Question 21

how do multicellular animals prevent osmosis catastrophes

Answer 21

blood plasma and the extracellular fluids of tissues are maintained at an osmolarity close to that of the cytosol of cells. Cells continually pump sodium ions out of the cytosol into the plasma to maintain osmotic balance

Question 22

turgor pressure

Answer 22

very high solute concentration in their vacuole which produces osmotic pressure
- helps draw water into plant cells