Molarity, Molality, Normality, and Mass Percent Worksheet II Answer Key 11-12.pdf

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