1. 7.85 kg KCl are dissolved in 2.38 L of solution. Find molality. 24.8 g table sugar (i.e., sucrose, C 12 H 22 O 11 ) are mixed into 450 g water. Find molality. WRONG

2. 1 mol CaF 2 2 atoms F 18 g 6.02 x 10 23 molecules 1 g1000 mL What mass of CaF 2 must be added to 1,000 L of water so that fluoride atoms are present at a conc. of 1.5 ppm? = 3.34 x 10 28 m’cules H 2 O X m’cule H 2 O = 1000 L 1 L1 mL 1 mol6.02 x10 23 m’cule 1 mol 1.5 atom F X atoms F 1,000,000 m’cule H 2 O 3.34 x 10 28 m’cule H 2 O = 1 molecule CaF 2 X = 5.01 x 10 22 atoms F times =2.505 x 10 22 molecules CaF 2 1 mol CaF 2 X g CaF 2 = 2.505 x 10 22 molecules =3.25 g CaF 2 78.1 g CaF 2

3. 40.0 g NaOH 1 mol NaOH How many moles solute are required to make 1.35 L of 2.50 M solution? mol = M L B. What mass magnesium phosphate is this? A. What mass sodium hydroxide is this? mol L M 3.38 mol = 2.50 M (1.35 L) = X g NaOH = 3.38 mol NaOH = 135 g NaOH 262.9 g Mg 3 (PO 4 ) 2 1 mol Mg 3 (PO 4 ) 2 X g Mg 3 (PO 4 ) 2 = 3.38 mol Mg 3 (PO 4 ) 2 = 889 g Mg 3 (PO 4 ) 2

4. 0.342 mol 5.65 L Find molarity if 58.6 g barium hydroxide are in 5.65 L solution. 171.3 g Ba(OH) 2 1 mol Ba(OH) 2 Step 2). What is the molarity of a 5.65 L solution containing 0.342 mol solute? Step 1). How many moles barium hydroxide is this? 0.061 M Ba(OH) 2 = X mol Ba(OH) 2 = 58.6 g Ba(OH) 2 = 0.342 mol Ba(OH) 2 M = mol L M =

5. You have 10.8 g potassium nitrate. How many mL of solution will make this a 0.14 M solution? convert to mL

6. Concentration SAWS Water Quality Report - June 2000

7. Molality mass of solvent only 1 kg water = 1 L water

8. Molality  Find the molality of a solution containing 75 g of MgCl 2 in 250 mL of water. 75 g MgCl 2 1 mol MgCl 2 95.21 g MgCl 2 = 3.2 m MgCl 2 0.25 kg water

9. Molality  How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water? 0.500 kg water1.54 mol NaCl 1 kg water = 45.0 g NaCl 58.44 g NaCl 1 mol NaCl

10. Molarity of Solutions Keys Molarity of Solutions http://www.unit5.org/chemistry/Solutions.html