UW Chem 162 Exam 2 with Accurate
Solutions
molarity - ANSWER-mol solute/L solution
molality - ANSWER-mol solute/kg solvent
mole fraction - ANSWER-mol solute/(mol solute + mol solvent)
% by mass - ANSWER-mass solute/mass solution X 100%
% by volume - ANSWER-volume solute/volume solution X 100%
% mass to volume - ANSWER-mass solute(g)/volume solution(mL)
Gibbs Free Energy - ANSWER-G=H-TS
Hsolution - ANSWER-Hsolute + Hsolvent + Hmix
endothermic when Hendo - ANSWER-less than Hexo
exothermic when Hexo - ANSWER-less than Hendo
H mix always - ANSWER-opp sign of Hsolute and Hsolvent
predicting relative solubilities - ANSWER-like dissolves like!!!!
more charge density = - ANSWER-greater hydration
endothermic, T on solubility - ANSWER-solubility increases as T increases
exothermic, T on solubility - ANSWER-solubility decreases as T increases
gases, T on solubility - ANSWER-solubility decreases as T increases
Henry's Law - ANSWER-s=kHP
s = molar solubility of gas (mol/L)
kH = constant (mol/Latm)
P = partial pressure of gaseous solute (atm)
, Henry's law holds only if - ANSWER-there is no chemical reaction between the solute
and solvent and the soln is fairly dilute
For all gases, Hsolute = and Hsoln = - ANSWER-Hsolute=0, Hsoln<0
why do non-volatile solutes lower vapor pressure? - ANSWER-bc the dissolved solute
decreases the number of solvent molecules per unit volume/lowers the amount of
solvent volumes escaping the solution
Raoult's Law - ANSWER-Psolvent = XsolventPsolvent
Raoult's for volatile solutes - ANSWER-Ptotal = Psolute + Psolvent
boiling point definition - ANSWER-temp at which its vapor pressure equals atmospheric
pressure
non-volatile solutions & bp - ANSWER-higher bp
boiling point elevation - ANSWER-Tb=ikbbsolute
i = # of ions
kb=constant
bsolute=molality
in freezing point depression, the presence of solute - ANSWER-lowers the rate at which
molecules in the liquid return to the solid -- have to lower temp to decrease the rate of
molecules leaving the solid until the rates are equal
freezing point depression - ANSWER-Tf=ikfbsolute
i = # of ions
kf = constant
bsolute = molality
osmotic pressure - ANSWER-pi = iRTc
i = # of ions
R = 0.0821 Latm/molK
c = molar concentration of solute
ideal behavior - ANSWER-approached when solute and solvent are involved n similar
intermolecular interactions (Hsoln=0)
weaker solute-solvent interactions - ANSWER-heat is removed upon dissolving
Hsoln>0
endothermic
negative temp
positive deviation from Raoul's
observed vap press higher than ideal
Solutions
molarity - ANSWER-mol solute/L solution
molality - ANSWER-mol solute/kg solvent
mole fraction - ANSWER-mol solute/(mol solute + mol solvent)
% by mass - ANSWER-mass solute/mass solution X 100%
% by volume - ANSWER-volume solute/volume solution X 100%
% mass to volume - ANSWER-mass solute(g)/volume solution(mL)
Gibbs Free Energy - ANSWER-G=H-TS
Hsolution - ANSWER-Hsolute + Hsolvent + Hmix
endothermic when Hendo - ANSWER-less than Hexo
exothermic when Hexo - ANSWER-less than Hendo
H mix always - ANSWER-opp sign of Hsolute and Hsolvent
predicting relative solubilities - ANSWER-like dissolves like!!!!
more charge density = - ANSWER-greater hydration
endothermic, T on solubility - ANSWER-solubility increases as T increases
exothermic, T on solubility - ANSWER-solubility decreases as T increases
gases, T on solubility - ANSWER-solubility decreases as T increases
Henry's Law - ANSWER-s=kHP
s = molar solubility of gas (mol/L)
kH = constant (mol/Latm)
P = partial pressure of gaseous solute (atm)
, Henry's law holds only if - ANSWER-there is no chemical reaction between the solute
and solvent and the soln is fairly dilute
For all gases, Hsolute = and Hsoln = - ANSWER-Hsolute=0, Hsoln<0
why do non-volatile solutes lower vapor pressure? - ANSWER-bc the dissolved solute
decreases the number of solvent molecules per unit volume/lowers the amount of
solvent volumes escaping the solution
Raoult's Law - ANSWER-Psolvent = XsolventPsolvent
Raoult's for volatile solutes - ANSWER-Ptotal = Psolute + Psolvent
boiling point definition - ANSWER-temp at which its vapor pressure equals atmospheric
pressure
non-volatile solutions & bp - ANSWER-higher bp
boiling point elevation - ANSWER-Tb=ikbbsolute
i = # of ions
kb=constant
bsolute=molality
in freezing point depression, the presence of solute - ANSWER-lowers the rate at which
molecules in the liquid return to the solid -- have to lower temp to decrease the rate of
molecules leaving the solid until the rates are equal
freezing point depression - ANSWER-Tf=ikfbsolute
i = # of ions
kf = constant
bsolute = molality
osmotic pressure - ANSWER-pi = iRTc
i = # of ions
R = 0.0821 Latm/molK
c = molar concentration of solute
ideal behavior - ANSWER-approached when solute and solvent are involved n similar
intermolecular interactions (Hsoln=0)
weaker solute-solvent interactions - ANSWER-heat is removed upon dissolving
Hsoln>0
endothermic
negative temp
positive deviation from Raoul's
observed vap press higher than ideal
