Ch. 5 - Solutions

 The amount of solute in a solution.
 Describing Concentration
 % by mass - medicated creams
 % by volume - rubbing alcohol
 ppm, ppb - water contaminants
 molarity - used by chemists

CONCENTRATION – compares the quantity of solute to the quantity of solvent
A dilute solution has a relatively small quantity of solute per unit volume of solution.
A concentrated solution has a relatively large quantity of solute per unit volume of solution.

1.
% by volume
= volume of solute x100% volume of solution
Example problem: 10mL of fresh orange juice are mixed with 100mL of water. What is the % by volume of orange juice?(9.1%)

2.ppm: This is only used for very small amounts of solute.
= mass of solute x 10⁶
Mass of solution
Example problem: 400g of water has 5.6 x10 -3 g of lead. What is the concentration in ppm?(14ppm)

3Amount Concentration: Used mostly in Chemistry
= Moles of solute
Volume in L.
Example problem: 12g of NaCl are dissolved in 12.3mL of water. What is the molarity of the solution?
(17M)

Amount Concentration (Molarity)

2
O )
0.25M

0.25 mol
1 L volume of solvent only

Amount Concentration (Molarity)
Find the molarity of a solution containing 75 g of MgCl
2 in 250 mL of water.
75 g MgCl
2
0.250 L
1 mol MgCl
2
95.21 g MgCl
2
M
 mol
L
= 3.2
M MgCl
2

Amount Concentration (Molarity)
How many grams of NaCl are required to make a
1.54M solution using 0.500 L of water?
1.54 mol NaCl
L 1 mol NaCl
M
 mol
L
= 45.0 g NaCl

8. List the chemical formulas for the major entities present in water for each of the following:
(a) Zinc
(b) potassium dichromate
(c) sodium bromide
(d) acetic acid
(e) oxygen
(f) Sulfur
(g) nitric acid
(h) copper(II) sulfate
(i) calcium phosphate
(j) silver chloride
(k) methanol
(l) paraffin wax, C
25
H
52(s)
(m) aluminum sulfate

Write dissociation or ionization equations for the following
1.
2.
3.
4.
5.

What is the concentration of Calcium and Chloride ions in a 0.30mol/L solution of CaCl
2
CaCl
2
(aq) → Ca +2 (aq) + 2 Cl -1 (aq)
15

What are the ion concentrations of the following?
1. 0.125 M sodium hydroxide
2. 0.500 M ammonium phosphate
3. 1.35 M sulfuric acid
4. 0.0150 M perchloric acid
5. 0.246M dihydrogen phosphate ion concentration in a sodium dihydrogen phosphate solution.
M

# mol
L

Page 212 # 17-19

 Adding solvent (solute is unchanged) to decrease the concentration of a solution
 Dilution Formula: C
1 x V
1
= C
2 x V
2
 C = Concentration, V = Volume (Liters)
18

 Water is added to 0.200L of 2.4 mol/L cleaning solution until the final volume is 1.00L. What is the new concentration?
 Dilution worksheet and p216/218 # 1,2,6,7

Figure 14.7: Preparation of a standard aqueous solution
20

Figure 14.8: Acetic acid dilution
21

END

3.
1.
2.
4.
Calculate the number of moles of HCl in 260mL of 0.24M solution.
Calculate the concentration of a solution with
6.2moles of HCl in 45mL of solution.
Calculate the volume if you have 0.12moles of
3.2M HCl
Calculate the g of potassium nitrate in 23mL of
6.2M solution
23

1.
What is the concentration of a solution if 10.6g of Potassium carbonate are dissolved in 45mL of water? (2 marks)
2.
3.5L of 6.2M HCl are evaporated to give 56mL.
What is the new concentration of HCl? (2 marks)
3.
2L of water is added to 6L of 0.2M HCl. What is the new concentration? (2 marks)
4.
The technician has 36M HCl which is way too strong for Ms Portman’s class. They need 50mL of 2M HCl for their lab. What should he do????
(2marks)
24