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Honors Chemistry Chapter 12: Molarity, Molality, Normality, and Mass Percent Worksheet II
Name ____________________________________ Date _____/_____/_____
Period _____
Molarity = Moles of solute / Liters of Solution (abbreviation = M) Molality = Moles of solute / Kg of Solvent (abbreviation = m) Normality = number of equivalent of solute x Molarity of Solution (abbreviation = N) Mass Percent = mass of solute / mass of solution 1. How many moles of of ethyl alcohol, C 2H5OH, are present in 65 mL of a 1 .5 M solution? 65 mL C2H5OH
1 L C2H5OH 1000 mL C 2H5OH
1.5 mole C2H5OH 1 L C2H5OH
= 0.098 moles C 2H5OH
2. How many liters of a 6 .0 M solution of acetic acid CH 3COOH, contain 0. 0 .0030 moles of acetic acid? 0.0030 moles CH 3COOH
1 L solution 6.0 moles CH 3COOH
= 5.0 x 10 -4 L solution
3. You want 85 g of of KOH. KOH. How much of a 3 .0 m solution of KOH will provide it? 85 g KOH
1 mole 56.11 g KOH
5.0 x 10 2 g solvent
+
1 kg solvent 3.0 mole KOH
85 g KOH
=
1000 g solvent 1 kg solvent
= 5.0 x 10 2 g solvent
590 g solution
4. If you dissolve 0 .70 moles of HCl in enough water to prepare 250 mL of solution, what is the molarity of the solution you have prepared? M
=
0.70 moles HCl 0.250 L solution
=
2.8 M HCl
5. A solution is prepared by adding 2. 2 .0 L of 6. 6 .0 M HCl to 500 mL of a 9 .0 M HCl solution. What is the molarity of the new solution? (Remember, the volumes are additive) 2.0 L solution
6.0 moles HCl 1 L solution
0.500 L solution
9.0 moles HCl 1 L solution
= 4.5 moles HCl
12 moles HCl
+
4.5 moles HCl
2.0 L solution
+
0.500 L solution
M
=
= 12 moles HCl
17 moles 2.5 L solution
=
=
17 moles =
2.5 L solution
6.8 M HCl
6. Convert the following Molarities to Normalities. Normalities . a. 2.5 M HCl = 2.5
N
b.
1.4 M H2SO4
=
2.8
N
c.
1.0 M NaOH
=
1.0
N
d.
0.5 M Ca(OH) 2
=
1
N
7. A commonly purchased disinfectant is a 3 .0% (by mass) solution of hydrogen peroxide (H 2O2) in water. Assuming the density of the solution is 1.0 g/cm 3, calculate the molarity and molality of H 2O2. Mass %
=
3.0 g H2O2 100. g solution
3.0 g H2O2
1 mole H2O2 34.02 g H 2O2
100. g solution
M
=
x 100
= 0.088 mole H 2O2
1 mL solution 1.0 g solution
0.088 mole H 2O2 0.10 L solution
=
1 L solution 1000 mL solution
= 0.10 L solution
0.88 M H2O2
100. g solution - 3.0 g solute = 97 g solvent = 0.097 kg solvent m
=
0.088 mole H 2O2 0.097 kg solvent
=
0.91 m H2O2
8. A solution is made by dissolving 25 g of NaCl in enough water to make 1 .0 L of solution. Assume the density of the solution is 1 .0 g/cm3. Calculate the molarity and molality of the solution. 25 g NaCl
M
=
1 mole NaCl 58.44 g NaCl
0.43 mole NaCl 1.0 L solution
1.0 L solution
= 0.43 mole NaCl
=
0.43 M NaCl
1000 mL solution 1 L solution
1.0 g 1 cm 3 (or 1 mL)
1.0 x 10 3 g solution - 25 g
=
M
0.43 m NaCl
=
0.43 mole NaCl 1.0 kg solvent
=
= 1.0 x 10 3 g solution
1.0 x 10 3 g solute = 1.0 kg solute
9. What is the mass percent of a solution that contains 152 g of KNO 3 in 7.86 L of water?
7.86 L H2O
7860 g H2O
1000 mL H 2O 1 L H2O
+
152 g KNO 3
152 g KNO3 x 100 8010 g solution
=
=
1.000 g H2O 1 mL
8010 g solution
1.90 %
= 7860 g H 2O
10. A solution has been prepared to be 9 .00 % (by mass) glucose. For every 100.0 grams of solution present there are 9.00 g glucose grams of glucose. mass %
= 9.00 g glucose 100. g solution
x
100
11. How many grams of KBr are contained in 250 . grams of a 6.25 % KBr solution? 6.25 %
=
x x 100 250. g solution
x = 15.6 g KBr 12. What is the concentration of each type of ion and total concentration of ions in a 0 .375 M Ammonium phosphate solution? 0.375 mole (NH 4)3PO4 1 L solution
3 mole (NH 4)+1 1 mole (NH 4)3PO4
= 1.13 M (NH4)+1
0.375 mole (NH 4)3PO4 1 L solution
1 mole (PO 4)-3 1 mole (NH 4)3PO4
= 0.375 M (PO4)-3
1.13 M (NH4)+1
+
0.375 M (PO4)-3
=
1.51 M ions
13. How many moles of chloride ions are in 1 .50 L of 4.15 M zinc chloride? 1.50 L solution
4.15 mole ZnCl 2 1 L solution
ANSWERS 1. 0.098 moles of alcohol 2. 5.0 x 10-4 L solution 3. 5.9 x 10 2 g solution 4. 2.8M 5. 6.8 M 6. a. 2.5 N b. 2.8 N c. 1.0 N d. 1 N
2 mole Cl -1 1 mole ZnCl 2
= 12.5 mole Cl-1
7. 0.88M, 0.91m 8. 0.43M, 0.43m 9. 1.90 % by mass of KNO 3 10. 9.00 11. 15.6 g KBr 12. a. 1.13 M of (NH 4)+1 and 0.375 M of (PO 4)-3 b. 1.51 M of ions 13. 12.45 moles of Cl -1
