Practise Concentration of solutions. 14 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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concentration in g/dm3 = mass of solute in g ÷ volume of solution in dm3 How many cm3 are there in 0.250 dm3?
250 cm3
Name the piece of apparatus used to weigh the solid solute accurately.
(electronic) balance
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
The concentration of a solution can be calculated using the equation: concentration in g/dm3 = mass of solute in g ÷ volume of solution in dm3
(a) A student dissolved 12 g of sodium chloride in water to make 0.50 dm3 of solution. Calculate the concentration of the solution.[2]
(b) How many cm3 are there in 1 dm3?[1]
(c) Calculate the mass of solute in 2.0 dm3 of a solution with a concentration of 15 g/dm3.[2]
Show the answer and mark scheme
(a)Answer: 24 g/dm3
12 ÷ 0.50
24 (g/dm3)
(b)Answer: 1000
1000
(c)Answer: 30 g
15 × 2.0
30 (g)
Question 2Medium6 marks
Many chemical reactions take place in solutions. The concentration of a solution can be measured in g/dm3.
(a) A student dissolved 5.0 g of copper sulfate in water to make 250 cm3 of solution. Calculate the concentration of the solution in g/dm3.[2]
(b) Calculate the mass of sodium hydroxide in 25.0 cm3 of a solution with a concentration of 40 g/dm3.[2]
(c) A student needs 3.0 g of potassium nitrate. The student has a solution of potassium nitrate with a concentration of 60 g/dm3. Calculate the volume of solution, in cm3, that contains 3.0 g of potassium nitrate.[2]
Show the answer and mark scheme
(a)Answer: 20 g/dm3
250 cm3 = 0.25 dm3
5.0 ÷ 0.25 = 20 (g/dm3)
(b)Answer: 1.0 g
40 × 0.0250
1.0 (g)
(c)Answer: 50 cm3
3.0 ÷ 60 = 0.05 (dm3)
50 (cm3)
Question 3Hard8 marks
A student needs to make 250 cm3 of sodium carbonate solution with a concentration of 10.6 g/dm3.
(a) Calculate the mass of sodium carbonate the student needs.[2]
(b) Describe how the student should make the solution so that its concentration is accurate. Include the names of the apparatus used.[6]
Show the answer and mark scheme
(a)Answer: 2.65 g
10.6 × 0.250
2.65 (g)
(b)
weigh 2.65 g of sodium carbonate on a balance (reading to at least 0.01 g), e.g. in a weighing boat
reweigh the empty weighing boat / weigh by difference to find the mass actually transferred
dissolve the solid in a small volume of distilled / deionised water in a beaker, stirring with a glass rod
pour the solution into a 250 cm3 volumetric flask through a funnel
rinse the beaker, rod and funnel with distilled water and add the rinsings to the flask (so no solute is lost)
add distilled water until the bottom of the meniscus is on the graduation line, adding the last few drops with a dropping pipette
stopper the flask and invert it several times to mix the solution
use the mass actually transferred to calculate the exact concentration
Marked with levels of response: the full level descriptors are in the app.