MODULE 3
18
WORKSHEET
DILUTION CALCULATIONS
Syllabus reference 8.4.4
Frequently we need to dilute a solution from one concentration to a lower one. This is done by
measuring out a known volume of the original solution and adding water to make a new volume. In
the process the number of moles of solute is unchanged, only the concentration has decreased.
The following formula can be used to calculate concentrations and volumes in dilutions where c1 and
V1 are the original concentration and volume of solute and c2 and V2 are the new concentration and
volume.
c1V1  c2V2
1
The volume of solution in column A was diluted to the volume in column B. Calculate the molarity
of the diluted solution.
COLUMN A
a
a
50 mL 0.242 mol L–1 hydrochloric acid
b
25 mL 0.152 mol L–1 sulfuric acid
c
10 mL 0.114 mol L–1 sodium hydroxide
COLUMN B
500 mL
2.0 L
250 mL
0.242  50  c2  500
c2  0.0242 mol/L
b
0.152  25  c2  2000
c2  1.09  103 mol/L
c
0.114  10  c2  250
c2  4.56  103 mol/L
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 18
2
What volume of solution in column A in the following table is needed to prepare the solution in
column B?
COLUMN A
3
COLUMN B
a
0.282 mol L–1 hydrochloric acid
b
2.42 mol L–1 sulfuric acid
2.0 L 0.121 mol L–1
c
0.318 mol L–1 sodium hydroxide
1.0 L 0.300 mol L–1
a
10.0 mL
b
100 mL
c
943 mL
250 mL 0.0113 mol L–1
50 mL 0.20 mol L–1 sodium hydroxide was mixed with 50 mL 0.30 mol L–1 magnesium chloride.
A precipitate of magnesium hydroxide formed.
Calculate the concentration of:
2NaOH  MgCl2
a
2NaCl  Mg(OH)2
sodium ions
n(NaOH)  0.20  0.050  0.010 mol
b
magnesium ions
originally n(MgCl2)  0.30  0.050  0.015 mol
n(Mg(OH)2) precipitated  0.005 mol
n(Mg2)  0.015  0.005  0.010 mol
c
chloride ions
n(Cl)  0.015  2  0.30 mol
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 18