Calculation of concentration and solubility

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Link to the lesson

Before you start you should know

that the solubility in water is expressed as the maximum number of grams of substance that is dissolved in 100 g of water at a given temperature and pressure (the pressure is taken into account in the case of gas solutions, e.g. oxygen in water, and when the solute is solid or liquids, the pressure is of little importance and can be omitted);
that the graph showing the dependence of the solubility of a given substance on the temperature is called the solubility curve;
that the percentage determines the number of grams of solute contained in 100 grams of solution and can be calculated from the formula: $C_{p} = \frac{m_{s}}{m_{r}} · 100%$ .

You will learn

to calculate the percentage concentration of a saturated solution at a given temperature using a solubility chart
to determine the solution solubility based on the percentage of saturated solution at a given temperature

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How we calculate the percentage of saturated solution?

The solution saturated at a given temperature contains a defined amount of solute in a given mass of solvent. On the basis of these values, the percentage concentration of the solution can be calculated.

Size	Solubility	Weight of the solution	Percent concentration
importance	the maximum mass of substance that can be dissolved in 100 g of water at a given temperature	$m_{r} = m_{s} + m_{rozp.}$	$C_{p} = \frac{m_{s}}{m_{r}} · 100%$

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Exercise 1

Calculate the percentage of the saturated copper(II) sulphate solution at 80°C.

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Answer

Exercise 2

Which saturated solution has a higher percentage: sodium chloride at 50°C or sodium nitrate at 10°C? Make the right calculations that will answer this question.

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Answer

The more mass of solute falls on a specific mass solventsolventsolvent, the percentage concentration of the solution is higher. Due to the fact that the solubility of solids usually increases with temperature, the concentration of the saturated solution of these substances also increases.

How we calculate the solubility of a substance in a saturated solution with a known percentage concentration?

If at a given temperature we know the percentage of saturated solution of a substance, then we can calculate the solubility of this substance at a certain temperature.

Task 1

Before solving tasks, watch the presentation, it will guide you through the process of solving the task.

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Grafika slajdu, na niebieskim tle tytuł: Stages of solving the task for calculating the solubility of substances in a saturated solution with a known percentage concentration. — Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia zlewkę wypełnioną wodą, szalkę Petriego z substancją w kolorze białym, szpatułkę oraz termometr. — Calculate the solubility of a substance at 70 ° C, if the solution saturated at this temperature has a concentration of 38.5%.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia problem obliczeniowy - należy obliczyć masę wody oraz masę substancji w stu gramach roztworu. Podane są informacje: 1. mass of water i 2. mass of the substance in 100 gram of solution. — We calculate the mass of water and the mass of the substance in 100 g of solution.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia obliczenia. W stu gramach roztworu mieści się trzydzieści osiem i pół grama substancji rozpuszczonej i sześćdziesiąt jeden i pół gramów wody. 100 gram of the solution contains 38,5 gram of solute. em es = 38,5 gram, em w, mass of water = em er minus em es, em w = 100 g - 38,5 g = 61,5 g — From the definition of the percentage concentration, we interpret that in 100 g of the solution there is 38.5 g of solute, i.e. m_s= 38,5 g. So the mass of water: m_r - m_s.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia stosunek masy rozpuszczonej do rozpuszczalnika. Jest on stały. Calculation of the maximum mass of substance that can dissolve in 100 gram of water. Wzór: w liczniku mass of solute, w mianowniki solvent mass = constant value. — Calculation of the maximum mass of substance that can dissolve in 100 g of water.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Ilustracja przedstawia działania przeprowadzone na konkretnych wartościach - proporcję: trzydzieści osiem i pół grama podzielone na sześćdziesiąt jeden i pół grama równa się iks gramów podzielone na sto gramów. Z proporcji należy obliczyć iks. Iks równa się trzydzieści osiem i pół grama pomnożone przez sto gramów podzielić na sześćdziesiąt jeden i pół gramów, co daje wynik sześćdziesiąt dwa i pół gramów. Rozpuszczalność omawianej substancji w wodzie w temperaturze siedemdziesięciu stopni wynosi sześćdziesiąt dwa i pół grama. The solubility of the substance at 70 Celsius degrees is 62,6 gram. — Re. The solubility of the substance at 70 ° C is - 62.6 g.
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.

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Exercise 3

Calculate the solubility of the substance at 50°C, if the solution saturated at this temperature has a concentration of 53.27%.

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Answer

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Exercise 4

Preparing a solution of potassium nitrate in water, the student noticed that at a temperature of 60°C, a small amount of crystals remained at the bottom of the vessel. What should I do to let these crystals dissolve? Highlight the right answers:

pour off some of the solution
top up with water
heat the solution
evaporate a small amount of water.

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Create a multiple-choice test based on today's lesson. Then exchange your questions with a friend or classmate.

Question: ...

Summary

Based on the knowledge of the solubility of the substance, the percentage of saturated solution can be calculated.
Knowing the percentage concentration of a saturated solution of a substance, you can calculate its solubility.

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

Keywords

percentage concentration of the solution, solvent

Glossary

percentage concentration of the solution

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nagranie dźwiękowe słówka

stężenie procentowe roztworu – jest to liczba gramów substancji zawarta w 100 gramach roztworu, wyrażona w procentach

solvent

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nagranie dźwiękowe słówka

rozpuszczalnik – ciecz zdolna do tworzenia roztworu po zmieszaniu z ciałem stałym, inną cieczą lub gazem

Lesson plan (Polish)

How we calculate the percentage of saturated solution?

How we calculate the solubility of a substance in a saturated solution with a known percentage concentration?

Summary

Keywords

Glossary