Formula sheet Chapter 14 Calculations of Solutions
M=
m=
“molar”
“molal”
For % convert mole to grams, for % by volume density may be necessary.
For molarity, molality and mole fraction convert grams to mole!
Watch out for the different denominators for M: volume of total solution and for m: kg of solvent only
Dilution equation: M1V1 = M2V2
Henry’s law
(M = molarity, V = volume)
(V2 = V1 of stock solution + solvent (usually water))
Henry’s law states that at a given temperature,
the solubility (S) of a gas in a liquid is directly
proportional to the pressure (P).
i Kb m
i represents the # of dissolved particles per formula of solute
For Water:
Kb = 0.512
Kf = 1.86
i Kf m
i represents the # of dissolved particles per formula of solute
Practice problems for %, molarity, molality, dilution and mole fraction
1) If 0.50 mol NaOH is dissolved in 750g of water, what is the percent by mass of NaOH?
2) A 750. mL bottle of wine is labeled 12.8 % alcohol (v/v). How many mL ethanol are in the bottle?
3) How many moles of lithium chloride are in 2.00 L of 2.50 M LiCl?
4) How many grams of solute are in 2250 mL of 1.50 M CaCl2?
5) a)How many mL of 4.00 M KI solution would you need to prepare 250.0 mL of 0.760M KI?
b) Approximately, how much water would you add?
6) What is the molality(m) of a solution in which 35g of I2 is dissolved in 1500 g of ethanol?
7) An aqueous HBr solution contains 17.75% (by mass) HBr. What is the mole fraction of HBr?
(assume 100g of solution  17.75g HBr and 100 – 17.75 = 82.25g H2O. Convert both to mol…)
[1) 2.6%, NaOH, 2) 96.0mL ethanol, 3) 5 mol LiCl, 4) 375 g CaCl 2, 5) a) 47.5mL (b) 202.5 mL 6) 0.092m, 7) .04586]