.​​Solutions Unit – Extra Review
Formulas Needed:
 ∆ tf = m * Kf*n , ∆ tb = m * Kb*n, (see Weebly update 4/26, Kf is from chart p438)
Molarity: M = mols of solute/ L of solvent
Molality: m = mols of solute/ kg of solvent ** water is the universal solvent
Freezing Point:  f.p. solution = f.p. solvent + ∆ tf
Boiling Point: b.p. solution: b.p. solvent + ∆ tb (f.p. & b.p. solvent see p438)
 
1) Na2SO4 is dissolved in water to make 450mL of a 0.250M solution.  How many moles of Na2SO4 are needed to make this concentration?
 
2) How many grams of Na2SO4 are needed for the above solution?
 
3) If 74.6g of KCl are combined with water to create 350mL solution.  What is the molarity of this solution?
 
4)For Electrolytes(produced by the dissolution of an ionic compound, p432-433, 443-446):
Know how to write the equation for dissolution of an ionic compound in water:
             H20
NaNO3 ---> Na+ + NO3- ….The number of parts created is 2, n=2
 
5) TB Problem 19c)p449 (see sample prob 14-3)
Determine freezing point depression of H20 for 77.0g of C12H22O11 in 400.g of H20.
 
6) Calculate the expected freezing point of a solution containing 1.00kg of H2O and 0.25 mol of NaCl.
(an electrolyte)
 
7) A At what temperature will a solution that is composed of 0.73 moles of glucose,C6H12O6 in 225 g of phenol boil?
(Phenol is on f.p./ b.p. chart p438) 

​*** Review solubility graph for solids on p408

For HW  Formulas are: Tf = n Kf m    and Tb = n Kb m  
​ ( represents the triangle & textbook formula assumes n=1 and excludes n)
n= # of particles (how many parts the solute dissolves into)
Nonelectrolyte n=1, all of the textbook examples assume 1 particle
Strong Electrolytes, n=2 or more, ex:NaCl, n=2 bc 2 parts: Na & Cl
m=molality= mols solute/ kg solvent
Kf & Kb are constants found in the Molal Freezing Point/ Boiling Point Chart on p438,
​ex: water freezing pt = 0 degrees C and water's Kf = -1.86 deg C/m

****HW: p447, #13a, 19a, 25a, 29****  Alt Assignment: 13b, 19c, 25c, 30

Answers to Prob 5 & 6 were typed up wrong -CORRECT ANS: 5) 1.26 mol      6) 6.47 atm