UW CHEM 162 EXAM 2 QUESTIONS
AND ANSWERS
molarity - Correct Answers -mol solute/L solution
molality - Correct Answers -mol solute/kg solvent
mole fraction - Correct Answers -mol solute/(mol solute + mol solvent)
% by mass - Correct Answers -mass solute/mass solution X 100%
% by volume - Correct Answers -volume solute/volume solution X 100%
% mass to volume - Correct Answers -mass solute(g)/volume solution(mL)
Gibbs Free Energy - Correct Answers -G=H-TS
Hsolution - Correct Answers -Hsolute + Hsolvent + Hmix
endothermic when Hendo - Correct Answers -less than Hexo
exothermic when Hexo - Correct Answers -less than Hendo
freezing point depression - Correct Answers -Tf=ikfbsolute
i = # of ions
kf = constant
bsolute = molality
osmotic pressure - Correct Answers -pi = iRTc
i = # of ions
R = 0.0821 Latm/molK
c = molar concentration of solute
ideal behavior - Correct Answers -approached when solute and solvent are involved n
similar intermolecular interactions (Hsoln=0)
H mix always - Correct Answers -opp sign of Hsolute and Hsolvent
predicting relative solubilities - Correct Answers -like dissolves like!!!!
, more charge density = - Correct Answers -greater hydration
endothermic, T on solubility - Correct Answers -solubility increases as T increases
exothermic, T on solubility - Correct Answers -solubility decreases as T increases
gases, T on solubility - Correct Answers -solubility decreases as T increases
Henry's Law - Correct Answers -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 - Correct Answers -there is no chemical reaction between the
solute and solvent and the soln is fairly dilute
For all gases, Hsolute = and Hsoln = - Correct Answers -Hsolute=0, Hsoln<0
why do non-volatile solutes lower vapor pressure? - Correct Answers -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 - Correct Answers -Psolvent = XsolventPsolvent
Raoult's for volatile solutes - Correct Answers -Ptotal = Psolute + Psolvent
boiling point definition - Correct Answers -temp at which its vapor pressure equals
atmospheric pressure
non-volatile solutions & bp - Correct Answers -higher bp
boiling point elevation - Correct Answers -Tb=ikbbsolute
i = # of ions
kb=constant
bsolute=molality
in freezing point depression, the presence of solute - Correct Answers -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
weaker solute-solvent interactions - Correct Answers -heat is removed upon dissolving
Hsoln>0
endothermic
negative temp
positive deviation from Raoul's
AND ANSWERS
molarity - Correct Answers -mol solute/L solution
molality - Correct Answers -mol solute/kg solvent
mole fraction - Correct Answers -mol solute/(mol solute + mol solvent)
% by mass - Correct Answers -mass solute/mass solution X 100%
% by volume - Correct Answers -volume solute/volume solution X 100%
% mass to volume - Correct Answers -mass solute(g)/volume solution(mL)
Gibbs Free Energy - Correct Answers -G=H-TS
Hsolution - Correct Answers -Hsolute + Hsolvent + Hmix
endothermic when Hendo - Correct Answers -less than Hexo
exothermic when Hexo - Correct Answers -less than Hendo
freezing point depression - Correct Answers -Tf=ikfbsolute
i = # of ions
kf = constant
bsolute = molality
osmotic pressure - Correct Answers -pi = iRTc
i = # of ions
R = 0.0821 Latm/molK
c = molar concentration of solute
ideal behavior - Correct Answers -approached when solute and solvent are involved n
similar intermolecular interactions (Hsoln=0)
H mix always - Correct Answers -opp sign of Hsolute and Hsolvent
predicting relative solubilities - Correct Answers -like dissolves like!!!!
, more charge density = - Correct Answers -greater hydration
endothermic, T on solubility - Correct Answers -solubility increases as T increases
exothermic, T on solubility - Correct Answers -solubility decreases as T increases
gases, T on solubility - Correct Answers -solubility decreases as T increases
Henry's Law - Correct Answers -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 - Correct Answers -there is no chemical reaction between the
solute and solvent and the soln is fairly dilute
For all gases, Hsolute = and Hsoln = - Correct Answers -Hsolute=0, Hsoln<0
why do non-volatile solutes lower vapor pressure? - Correct Answers -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 - Correct Answers -Psolvent = XsolventPsolvent
Raoult's for volatile solutes - Correct Answers -Ptotal = Psolute + Psolvent
boiling point definition - Correct Answers -temp at which its vapor pressure equals
atmospheric pressure
non-volatile solutions & bp - Correct Answers -higher bp
boiling point elevation - Correct Answers -Tb=ikbbsolute
i = # of ions
kb=constant
bsolute=molality
in freezing point depression, the presence of solute - Correct Answers -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
weaker solute-solvent interactions - Correct Answers -heat is removed upon dissolving
Hsoln>0
endothermic
negative temp
positive deviation from Raoul's
