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Syllabus
Syllabus
Many chemical reactions take place in solutions.
The concentration of a solution can be measured in grams per dm3 (g/dm3 ).
Students should be able to calculate the mass of solute in a given volume of solution of known concentration in terms of mass per given volume of solution
(HT only) explain how the mass of a solute and the volume of a solution is related to the concentration of the solution.
What does this mean?
What does this mean?
We dilute squash with water until it tastes right
One way to measure a concentration is the number of grams of solute (dissolved stuff) in each litre of water
Unfortunately, chemists write litres as dm3
So the unit would be grams per dm3 (g/dm3) rather than g/L which would be easier.
Example1.
Example1.
A student dissolves 16 g of salt in 2 dm3 of water what is the concentration?
Concentration = Mass/ volume = 16/2 = 8 g/dm3.
Example 2.
Example 2.
A student dissolves 16 g of salt in 200 cm3 of water what is the concentration?
Concentration = Mass/ volume
But first we need to know how many dm3 of water were used.
1000 cm3 = 1 dm3
So, 200 cm3 = 200/100 = 0.2 dm3
Concentration = g/ dm3 = 16/0.2 = 80 g/dm3.
Example 3.
Example 3.
A student has a salt solution with concentration 2.5 g/dm3.
What mass of salt in 4 dm3 of water?
Concentration = Mass/ Volume
So, Mass = Concentration x Volume
Mass = 2.5 x 4 = 10g
Example 4.
Example 4.
A student has a salt solution with concentration 3.5 g/dm3.
What mass of salt in 400 cm3 of water?
Concentration = Mass/ Volume
But first we need to know how many dm3 of water were used.
1000 cm3 = 1 dm3
So, 400cm3 = 400/1000 = 0.4 dm3
Mass = Concentration x Volume
Mass = 3.5 x 0.4 = 1.4 g
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