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Before you start you should know

that the percentage indicates how many grams of dissolved substance is in 100 grams of solution;
that the percentage concentration of the solution can be calculated based on the weight of the solution and the mass of solute, using the formula: $C_{p} = \frac{m_{s}}{m_{r}} · 100%$ ;
that the density of the solution determines the mass 1 cmIndeks górny 3this solution and that it is calculated based on the formula: $d = \frac{m_{r}}{V_{r}} [\frac{g}{{cm}^{3}}]$ .
how to calculate the percentage concentration of dilute solution.

You will learn

determine the percentage concentration of the solution after its concentration;
determine the percentage concentration of a solution formed after mixing two solutions of the same substance at different concentrations.

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Nagranie audio prezentujące proces zatężania roztworu. The process during which the amount of substance in the solution increases

The process during which the amount of substance increases in the solution

Sometimes, when drinking tea or other drink, we find that they are not sweet enough. Then we add another portion of sugar to them. We do the same with soup, which we consider to be quite salty – we also add it. In each case, we deliver the dissolved substance to its solutions. During these treatments, the amount of water does not change. The activity we do is an example of concentrationconcentration of the solutionconcentration.

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Ilustracja składa się z dwóch zdjęć umieszczonych obok siebie. Na pierwszym zdjęciu mężczyzna kucharz stojący przy kuchni próbuje metalową łyżką przeźroczystej substancji znajdującej się w metalowym garnku stojącym na kuchence. Na drugim zdjęciu kucharz w tej samej scenerii dodaje do garnka łyżkę białego proszku. — Too little amount of table salt in pickling cucumbers can make pickling these vegetables fail. Therefore, the cook always tastes the solution before using it and if necessary add another portion of salt

Task 1

Consider and answer what happens to the concentration of the substance during concentration.

In analytical laboratories, sometimes the amount of test substance in the solution is so small that attempts to detect it may fail. Therefore, very often before the analysis, the solvent is evaporated from the solution in order to increase the concentration of the test substance. Evaporation of the solvent is also a common process used in the food industry, eg during the production of sugar, concentrates, jams, concentrated stocks or juices.

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Ilustracja przedstawia mężczyznę w laboratorium chemicznym. Mężczyzna ma brodę, okulary nie jest ubrany w strój ochronny. Obsługuje specjalistyczny sprzęt laboratoryjny. — In chemical laboratories there is often a need to evaporate the solvent from solutions. This treatment is performed using a device called an evaporator

What happens in solutions during concentration?

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Ilustracja przestawia schemat przedstawiający zlewkę z niebieską cieczą. Po lewej stronie zlewki znajduje się w kole symulacja cieczy w przybliżeniu- składa się ona z dużej liczby małych niebieskich kropek oraz nielicznych większych pomarańczowych kropek. Pod zlewką znajduje się strzałka skierowana w dół, obok niej widać w małym płaskim naczyniu parowanie cieczy ze zlewki. Pod strzałką ponownie zaprezentowana jest zlewka z niebieską cieczą oraz schemat cieczy w przybliżeniu. Tym razem na schemacie znajduje się wiele pomarańczowych kuleczek rozmieszczonych pomiędzy drobnymi niebieskim kuleczkami. — The model of the solution concentration process by evaporation of the solvent. During the evaporation of the solvent from the solution, the number of solvent particles per diluted matter particles decreases. Thus, the mass of solvent relative to the mass of solute decreases

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Task 2

Watch the presentation „Stages of solving the task for calculating the concentration”. Pay attention to the methods of calculating the percentage when diluting the solution by adding water.

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Ilustracja przedstawia napisy: Stages of solving the task to calculate percentage concentration during the increasing concentration of the solution by evaporation of water. — How to calculate the percentage concentration during concentration of solution by evaporation of water? Let's check the example.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawiająca szklane naczynia chemiczne służące do pomiaru substancji chemicznych. Na pierwszym planie znajduje się zlewka, kolba oraz probówka wypełnione częściowo wodą. — 30g of water were evaporated from 70g of a 25% solution of sulphuric acid. What is the percentage concentration of the solution obtained?
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja zawiera napisy: Known: mw(mass of evaporated water)=30g, mr1(mass of solution)= 70g, cp1(percentage concentration)= 25%, Unknown cp2(percentage concentration)=?) — We are writing out data and searched based on the content of the task.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja zawiera napisy cp=msx100% dzielne na mr, ms= cp1xmr1 dzielone na 100%, ms=25%x70g dzielone na 100%=17,5g. — Let's use the formula, transform it and substitute our data into it. We calculate the mass of the substance contained in 25-percent solution - the first solution.
Source: Contentplus.pl sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia napisy: mr2= mr1- mw= 70g-30g=40g. — We calculate the mass of the solution after evaporation of water, i.e. the mass of the second solution - after concentration.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja zawiera napisy cp=ms razy 100% dzielone na mr, ms= cp1 razy mr1 dzielone na 100%, ms=25% razy 70g dzielone na 100%=17,5g — Knowing the mass of the substance calculated from the first solution and the mass of the solution after concentration, we calculate the concentration of the solution after concentration (after evaporation of water). The concentration of the newly obtained solution is 43.75%.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Nagranie dźwiękowe.

Exercise 1

21 g of sugar was added to 230 g of a 54% sugar solution. Calculate the percentage concentration of the resulting solution.

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Solution

Exercise 2

A 3% vinegar solution is used for preserving cucumbers. Calculate the mass ratio of mixing 6% vinegar with water to obtain the desired fill.

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Solution

Can we calculate the concentration of the solution resulting from the mixing of two solutions?

Sometimes we mix solutions of the same substance with each other. If the concentration of both solutions is the same, the solution after mixing will also have the same concentration.

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Ilustracja przedstawia trzy szklane butelki octu spirytusowego o stężeniu 10%. — 10% vinegar, regardless of where it was produced, always contains the same amount of acetic acid in a given mass of water

If, however, we mix solutions of the same substance with different concentrations, the concentration of the resulting solution will be different from the concentration of both solutions used. You can calculate them.

Task 3

Watch the presentation „Stages of solving the problem for calculating the percentage concentration when mixing solutions of two different concentrations according to the rule of St. Andrew”. Pay attention to the cross‑flow pattern in solving this type of tasks.

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Ilustracja zawiera napisy stages of solving the task to calculate percentage concentration when mixing solutions of two different concentrations according to the Rule of the Cross. — How to calculate the percentage when mixing solutions with two different concentrations? Let's check the example.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia szklane naczynia chemiczne, różnych kształtów służące do pomiaru substancji chemicznych. — Calculate the mass ratio of mixing a 20% sodium hydroxide solution with a 70% solution of this substance to obtain a 50% solution.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia schemat składający się z pięciu elementów cp1, cp2, cpx, x, y. Po lewej stronie wykresu znajdują się elementy cp1, cp2. cp1 strzałka w prawo do cpx, cp2 strzałka w prawo do cpx. Element cpx znajduje się w środkowej części schematu. Od elementu cpx znajdują się strzałki w prawo do elementów znajdujących się po lewej części schematu. Pierwsza strzałka do elementu x, druga strzałka do elementu y. — For such calculations, in practice, a cross-pattern is used, also called the Rule of the Cross. This is due to the inverse proportionality of the mass of the initial solution to the difference in concentrations of the initial and final solution.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia napisy : Known: cp1= 20%, cp2=70%, cpx=50%. Unknown:x dzielone na y=? — Let's write out our data and searched indicated in the content of the task.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja zawiera zapisy: x dzielone na y= 70%-50% dzielone na 50%-20%= 20% dzielone na 30%= 2 dzielone na 3. — Let's apply a cross rule, subtracting a smaller value from the larger concentration value.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja zawiera zapisy: x dzielne na y= 70%-50% dzielone na 50%-20%= 20% dzielone na 30%= 2 dzielone na 3. — Mix 2 mass parts of a 20% solution with 3 mass parts of 70% solution, i.e. a mass ratio is 2 to 3.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Nagranie dźwiękowe.

Exercise 3

Two sugar solutions were mixed together: 50 g of 6% and 40 g of 15%. Calculate the concentration of the resulting solution.

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Solution

We calculate the mass of sugar in both solutions.
Calculations for a 5% solution:

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Ilustracja prezentuje tabelę zawierającą dwie kolumny:1. The method using the percent concentration formula, ms= cpmr/100%= 5% 50g/100%=2,5g 2. The method using ratio. 100g-5g, 50g-xg, X= 50g5g/100g=2,5g

Calculations for a 12% solution:

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Ilustracja przedstawia tabelę. Tabela składa się z dwóch kolumn: The method using the percent concentration formula, ms= cpmr dzielone na 100%= 12%40g dzielone na 100%=4,8g. 2. The method using the ratio, 100g kreska pozioma 12g, 40g kreska pozioma xg, x= 40g12g dzielone na 100g=4,8g.

We calculate the total weight of sugar:
total mass of sugar = mass of sugar from a 5% solution + mass of sugar from a 12% solution = 2.5 g + 4.8 g = 7.3 g
We calculate the total mass of the solution resulting after mixing:
total solution weight = 50 g + 40 g = 90 g total solution weight = 50 g + 40 g = 90 g
Calculate the percentage concentration of the solution after mixing:

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Ilustracja zawiera napis cp=ms dzielone na mr razy 100%= 7,3g dzielone na 90g razy 100%=8,1%.

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Exercise 4

Indicate activities whose execution will increase the percentage value of a given solution:

evaporation of the solvent
addition of solvent
adding a solution with lower concentration
addition of substances
adding a solution with a higher concentration

Summary

The concentration of the solution may be varied by dilution or concentration.
As a result of dilution, the concentration of the solution decreases, and as a result of concentration – increases.
The solution can be diluted by adding a solvent to it.
Increasing the concentration of the solution occurs after evaporation of the solvent or the addition of a new portion of solute.
The concentration of the solution that will result from mixing solutions of the same substance but with different concentrations will differ from the concentrations of the solutions used to mix.

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Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

Keywords

percentage concentration of the solution, concentration change, solution, solvent, concentration of the solution

Glossary

concentration of the solution

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Nagranie słówka concentration of the solution.

zatężanie roztworu – zwiększenie stężenia roztworu w wyniku dodania do niego dodatkowej ilości substancji rozpuszczonej lub odparowania części rozpuszczalnika

solution dilution

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Nagranie słówka solution dilution.

rozcieńczanie roztworu – obniżenie stężenia roztworu, np. w wyniku dodania do niego rozpuszczalnika

Lesson plan (Polish)

Changing the concentration of the solution – concentration

The process during which the amount of substance increases in the solution

What happens in solutions during concentration?

Can we calculate the concentration of the solution resulting from the mixing of two solutions?

Summary

Keywords

Glossary