Dilutions
The process of adding a solvent, usually water, to a solution to make it less concentrated is called
dilution. It is used in chemistry to make solutions of a specific required concentration. Making dilutions
must be done precisely to ensure concentration is correct. Chemists use dilution as it is often more
convenient than making a brand new solution as it does not require weighing out and dissolving a
solute. The typical method is described below and illustrated here
The procedure involves the following steps.
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
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Using a pipette to measure the definite volume of a solution of known concentration
Transferring this volume to a volumetric flask
Adding water to the calibration line to make a solution of known concentration
Serial dilutions Watch the video Lesson 1 Dilutions year 11 chemistry
www.mrlongmanscience.weebly.com
Serial dilutions are especially useful in
experimental sciences where the
required concentration for an optimal
effect is not known. During Mr Longmans
honours project serial dilutions were
used to find the optimal quantity to
human DNA to insert into bacterial cells
in order to produce a protein. You can
see in the image on the left that serial
dilution of a DNA solution were made to
produce concentrations of 1.6, 0.8, 0.4
and 0.2µg/ml.
Calculations for Dilutions
As the number of moles of solute remains the same throughout we can use the Dilution formula to
obtain the final concentration of the solution.
Dilution formula
c1 V1 = c2 V2
Examples: Refer to your text Page 318 – worked example 7.4 for a worked example of using the
Dilution formula
Another more complex example if given here.
Example question: 10ml of an 18M solution of sulfuric acid was diluted with 140ml of water to make a
dilute sulfuric acid mixture. This new sulfuric acid solution was then reacted to completion with a 10M
sodium hydroxide solution. What was the volume of the sodium hydroxide solution?
H2SO4 + NaOH  NaHSO4 + H2O
H+ + OH-  H2O
Step 1. Find the concentration of final solution of H2SO4 (C2)
c1V1 = c2V2
18 x 0.01 = c2 0.150
c2 = 1.20M
Step 2. Calculate moles of H2SO4
n=
cxV
n = 1.20 x 0.150
n = 0.18 mol
Step 3 use reaction equation to find reaction ratio
1 H2SO4 : 1 NaOH
0.18mol (H2SO4) : 0.18 mol (NaOH)
Step 4 Volume of the NaOH Solution
n (NaOH) = c x V
0.18 = 10 x V
V = 0.0180 L  18.0 ml