Question

The amount of pollutants in air can best be expressed in terms of parts per million mass percentage mole fraction any of the above

Answer 1

Answer:

Solutions are homogeneous mixtures containing one or more solutes in a solvent. The solvent that makes up most of the solution, whereas a solute is the substance that is dissolved inside the solvent.

Relative Concentration Units

Concentrations are often expressed in terms of relative unites (e.g. percentages) with three different types of percentage concentrations commonly used:

Mass Percent: The mass percent is used to express the concentration of a solution when the mass of a solute and the mass of a solution is given:

Mass Percent=Mass of SoluteMass of Solution×100%(1)

Volume Percent: The volume percent is used to express the concentration of a solution when the volume of a solute and the volume of a solution is given:

Volume Percent=Volume of SoluteVolume of Solution×100%(2)

Mass/Volume Percent: Another version of a percentage concentration is mass/volume percent, which measures the mass or weight of solute in grams (e.g., in grams) vs. the volume of solution (e.g., in mL). An example would be a 0.9%( w/v)  NaCl  solution in medical saline solutions that contains 0.9 g of  NaCl  for every 100 mL of solution (see figure below). The mass/volume percent is used to express the concentration of a solution when the mass of the solute and volume of the solution is given. Since the numerator and denominator have different units, this concentration unit is not a true relative unit (e.g. percentage), however it is often used as an easy concentration unit since volumes of solvent and solutions are easier to measure than weights. Moreover, since the density of dilute aqueous solutions are close to 1 g/mL, if the volume of a solution in measured in mL (as per definition), then this well approximates the mass of the solution in grams (making a true reletive unit (m/m)).

Mass/Volume Percent=Mass of Solute (g)Volume of Solution (mL)×100%(3)

Explanation: