Week 2 Day 2 Solutions
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solute
thing being dissolved
solvent
thing doing the dissolving (often water, especially for our purposes)
solution
result of dissolving solute in solvent
molarity
M = moles (mol) of solute/liter (L) of solution *molarity uses volume of solution, not solvent ‘molar concentration’
molality
m = moles (mol) of solute/kgs (kg) of solvent *molality uses mass of solvent* ‘molal concentration’
Since molarity depends on temperature, as temperature increases, molar concentration will ____________.
Decrease (most things expand when heated)
Is molality temperature dependent?
No, mass does not depend on temp
Percent by weight to volume (%w/v)
(%w/v) = grams solute/100 ml solution
Percent by weight to weight (%w/w)
(%w/w) - grams of solute/100 g solution common use in tinctures
1 eqiuvalent (Eq) =
1 mole of “reactivity” i.e. 1 mole of Na+ = 1 Eq of Na+ 1 mole of Ca2+ = 2 Eq of Ca2+ (becasue it has a 2+ charge)
What is osmolarity?
sum of the molarities of all solutes in a solution i.e. osmolarity of a 1 M solution of NaCl is 2 Osm (NaCl is 2 Osm because it is two particles, Na + Cl —-> 1 particle = 1 vote in osmolarity)
Solubility
maximum amount of solute that will dissolve in a solvent aka - saturated solution units: mass/volume, g/L
supersaturated solution
contains more solute than allowed by the solubility creates unstable system, excess solute will come out of solution crystallizing as a solid, separting as a liquid or bubbling out as gas
‘delta Hsoln’
total energy change during dissolving of solute > 0 needs energy (endothermic) - feels cold < 0 gives off energy (exothermic) - feels hot
Of solids, liquids, and gases, which of the three state’s solubility is most affected by pressure?
Gas As pressure increases solubility of gaseous solute in a liquid solvent increases (Because solids and liquids are not very compressible, pressure has very little effect on the solutiblity of solid and liquid solutes)
Effect of temperature on solubility of liquids and solids.
Increased temp usually increases solubility of liquids and solids.
Effect of temperature on solubility of gases
Increased temp decreases solubility of gases remember caribbean water (clearer) vs Maine/Alaska ocean (cloudier) temp increases kinetic energy of particles—>more likely to escape out of solvent into gas particles
What are colligative properties?
properties of a solution that depend only on the number of solute particles, and not the identity of the solute particles
What are the 4 colligative properties of solution?
• vapor pressure decreases with increasing solute concentration • boiling point increases with increasing solute concentration • freezing point decreases with increasing solute concentration • osmotic pressure increases with increasing solute concentration
Henry’s Law
effect of pressure on solubility S = kH * Pgas S = solubility kH = Henry’s constant, specific for each gas and is temperature dependent Pgas = partial pressure for specific gas
How do colloids differ from solutions?
particles are larger and are suspended in solvent (not dissolved) these large particles reflect light, while dissolved molecules don’t
ppm
grams of solute/grams of solution X 1 x 10^6ppm OR approximately mg of solute/liters of solution