The measure of the amount of a certain solute dissolved in a certain volume of solution is called common concentration. So, this type of concentration is one of the ways to work the quantity or content of the components of a solution (mixture formed by a solute and a solvent).
In addition to concentration, there are several other ways to work the quantitative aspects of the solutions, like:
Molarity or concentration in quantity of matter;
Title or mass percentage;
Title or percentage by volume;
parts per million (ppm).
As it is a measure, the common concentration is nothing more than the mathematical relationship established between the mass of the solute dissolved in a certain volume of solution, being represented by the following mathematical expression:
C = m1
V
m1= mass of solute
V = volume of solution
Ç = common concentration
Units of measurement that routinely relate to the common concentration are listed below. It is worth noting that the first letter refers to the mass of the solute, and the second to the volume of the solution:
g/L (mass in grams and volume in liters). It is the most used unit;
mg/L (mass in milligrams and volume in liters);
g/ml (mass in grams and volume in milliliters);
mg/mL (mass in milligrams and volume in milliliters);
The common concentration is very present in our daily lives, such as when we use a nasal solution to unclog the nostrils, in the preparation of homemade serum or even when measuring the amount of glucose in the our blood. In all these cases, there is something in common: the dosage of the amount of solute dissolved in a certain amount of volume of solution.
See other examples of applying common concentration in some everyday situations.
Example 1: Phosphoric acid (H3DUST4) is a food additive used in the production of cola-type soft drinks, for example. The daily limit of phosphoric acid that can be ingested is 5 mg per kilogram of body weight. Calculate the volume in mL that a person weighing 50 kg should drink, knowing that the concentration of acid in the soda is 2 g/L.
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Data:
V =? mL
C = 2 g/L
daily limit = 5mg/kg
Person's mass = 50 kg
First we must determine the mass of H3DUST4 that the person can consume. To do this, we have to multiply the weight by the amount of potassium per kg:
m1 = 50.5
m1 = 250mg
If we apply the data in the formula, we will find common concentration:
C = m1
V
2 = 0,25
V
V = 0.125 L
For transform into mL, just multiply the value in liters by 1000:
V = 0.125,1000
V = 125 mL
Example 2: If we prepare a solution using 20 grams of sucrose (sugar) in 500 mL of water, what will be the common concentration, in g/L, of this solution after the end of the procedure?
Data:
m1 = 20 grams
V = 500 mL of solution
C = ?
We must, initially, transform the unit mL to liter, since the unit of concentration is in liters. To do this, just divide 500 by 1000:
V = 500
1000
V = 0.5 L
Finally, enough apply the formula of the common concentration:
C = m1
V
C = 20
0,5
C = 40 g/L
Example 3: If we find in a Chemistry laboratory a flask with 200 mL of an aqueous solution of chloride sodium (NaCl) and concentration equal to 250 g/L, what will be the mass of NaCl dissolved in these 200 mL of solution?
Data:
C = 250 g/L
m1 = ?
V = 200 mL
As the exercise wants to know what is the mass of NaCl dissolved in these 200 mL of solution, we must first change the mL unit to liter, as the concentration unit is in liters. To do this, just divide 200 by 1000:
V = 200
1000
V = 0.2 L
Finally, enough apply the formula of the common concentration:
C = m1
V
250 = m1
0,2
m1 = 50 g
Therefore, in 200 mL of solution, there are 50 grams of NaCl dissolved.
By Me. Diogo Lopes Dias
Would you like to reference this text in a school or academic work? Look:
DAYS, Diogo Lopes. "What is common concentration?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/quimica/o-que-e-concentracao-comum.htm. Accessed on June 28, 2021.
