In order to derive the mass of solute in a solution from its mass percentage, the mass of the solution must be known. Since the solution density isn’t greatly different from that of water (1 g/mL), a reasonable estimate of the HCl mass in 500 g (0.5 L) of the solution is about five times greater than that in a 100 g portion, or 5 × × 40 = 200 g. The HCl concentration is near 40%, so a 100-g portion of this solution would contain about 40 g of HCl. What mass of HCl is contained in 0.500 L of this solution? The density of this solution is 1.19 g/mL. “Concentrated” hydrochloric acid is an aqueous solution of 37.2% HCl that is commonly used as a laboratory reagent. The mass percentage of a solution component is defined as the ratio of the component’s mass to the solution’s mass, expressed as a percentage: Percentages are also commonly used to express the composition of mixtures, including solutions. Mass PercentageĮarlier in this chapter, percent composition was introduced as a measure of the relative amount of a given element in a compound. This section will describe some other units of concentration that are commonly used in various applications, either for convenience or by convention. However, molarity is only one measure of concentration. The previous section introduced molarity, a very useful measurement unit for evaluating the concentration of solutions.
W/v concentration is NOT the same as a %(w/v) concentration M/v concentration is NOT the same as a %(m/v) concentration Where x is the value of the percentage concentration This is true for other similar percentage concentrations:įor mass/volume percentage concentrations (m/v% or w/v%):įor mass/mass percentage concentrations (m/m% or w/w%):
We could write a mathematical expression equating parts per hundred (a percentage) and parts per million (ppm) as shown below: How would we convert that to a concentration in parts per million (ppm) ? This means that there are 9 000 parts of NaCl in every 1 000 000 parts of the solution.īut the concentration of a solution is sometimes given as a percentage.Ī percentage concentration tells you how many parts of solute are present in 100 parts of solution.įor example, the ethanol content in wine is often given as about 12%(v/v), that is, 12% of the volume of the wine is ethanol, or, there are 12 parts of ethanol in every 100 parts of solution. Recall that, in general, concentration tells you how much solute is present in a solution.Ī concentration in parts per million (ppm) tells you how many parts of solute are present in 1 000 000 parts of solution.įor example, a saline solution is a dilute aqueous solution of sodium chloride, NaCl (aq), with a concentration of 9 000 ppm. Parts per million and Percentage Concentration Calculations