Solvation, Solutions and Molarity

Question 1

Water is an effective solvent as…

Answer 1

it can
form hydrogen bonds.

Question 2

Water clings to…

Answer 2

polar molecules causing
them to be soluble in water.

Hydrophilic - attracted to water

Question 3

Water tends to exclude…

Answer 3

nonpolar molecules.

-Hydrophobic - repelled by water

Question 4

Hydrophilic:

Answer 4

water-loving.

– tend to dissolve in water

Question 5

Hydrophobic:

Answer 5

water-fearing.

– tend not to dissolve in water

Question 6

Amphipathic:

Answer 6

loving on both ends.

– molecules that contain one or more
hydrophobic and one or more hydrophilic
regions, e.g., sodium palmitate

Question 7

(add pg 76+)

Question 8

Hydrophilicity

Answer 8

• NaCl is an electrolyte
• Anions and cations
  are solvated
  differently in H2O
• Glucose is nonionic
  and hydrophilic

Question 9

Hydrophobic interactions are…

Answer 9

primarily entropy effect

Question 10

Hydrophobicity:

Answer 10

• Hydrophobic
  compounds and H2O
  don’t mix
• Amphipathic molecules
  are part hydrophobic
  and part hydrophilic

Question 11

Membranes and hydrophobicity

Answer 11

• Membranes
  surrounding cells
  and organelles
  exist because of
  hydrophobicity
• Membrane lipids
  are amphipathic
  molecules (part
  hydrophobic and
  part hydrophilic)

Question 12

Water is good solvent for…

Answer 12

polar
or ionized substances

Question 13

____ tend to dissolve in water

Answer 13

Ionic compounds (e.g. KCl) and polar covalent compound
(e.g. C2H5OH and CH3COCH3)

Question 14

The underlying principle of solvent properties of H2O is…

Answer 14

electrostatic attraction of unlike
charges; the positive dipole of water for the negative dipole
of another molecule, etc.

– ion-dipole interaction; e.g. KCl dissolved in H2O

– dipole-dipole interactions; e.g. ethanol or acetone
dissolved in H2O

– dipole-dipole induced interactions are weaker and
generally do not lead to solubility in water

Question 15

A mole is a counting unit

Answer 15

• Dozen = 12
• Score = 20
• Gross = 144
• Mole = 6.023 x 10^23

6.023 x 10^23 hydrogen atoms weigh one gram

6.023 x 10^23 sucrose molecules = 342 grams

Question 16

Molar is a unit of concentration:

Answer 16

• Molar = moles/liter.
• Example:
  [sucrose] in your Iced Tea
  – Glass = 500 mL

– 3 heaping teaspoons = 26 grams of sucrose

– Molecular Weight of sucrose = 342 g/mol

– [Sucrose] = 26 g / (342 g/mol) / 0.5 L = 0.152 M
or 152 mM