Learn to solve exercises on the physical units of the concentration of the chemical solutions, such as percentage in mass (mass to mass or weight to weight), percentage in volume (volume to volume), percentage mass to volume and parts per million.
Mass-mass percentage (% m / m) It is defined as the mass of solute (substance that dissolves) for every 100 units of mass of the solution. For example, if you dissolve 20 g of sugar in 80 g of water, the percentage by mass will be: [20 / (20 + 80)] x 100 = 20% or, to distinguish it from other percentages, 20% m / m
Percentage volume-volume (% v / v)
Express the volume of solute per hundred units of volume of the solution. It is usually used for liquid or gaseous mixtures, in which the volume is an important parameter to be taken into account. That is, the percentage represented by the solute in the total volume of the solution. It is usually simplified as "% v / v". For example, if you have a solution of 20% by volume (20% v / v) of alcohol in water it means that there is 20 ml of alcohol per 100 ml of solution. The alcohol content of beverages is expressed precisely as follows: a wine of 12 degrees (12 °) has 12% v / v alcohol.
Percentage in mass-volume (% m / v)
The same units can also be used to measure the density although it is not convenient to combine both concepts. The density of the mixture is the mass of the solution divided by the volume of this, while the concentration in these units is the mass of solute divided by the volume of the solution by 100. Grams are usually used per milliliter (g / ml ) and sometimes expressed as "% m / v".
Parts per million (ppm) is a unit of measure with which the concentration is measured. Determine a tolerance range. It refers to the number of units of a certain substance (agent, etc.) that there are per million units of the set. For example, in one million grains of rice, if one were painted black, this grain would represent one (1) part per million. It is abbreviated as "ppm".
21 авг 2024
