Question

Fill in the blank. Concentration of 1ppm means that 1L solution contains ________ mg solute.

Answer 1

Hint: The term “ parts per million” indicates the amount of solvent that is present in a million or parts of the solution. A solution consists of two parts, the solute(one which is present in low conc) and solvent( present in high conc).

Complete step-by-step solution:
In order to answer our question, we need to find out the methods of expressing the concentration of the solutions. Concentration of a solution means describing its composition. Qualitatively, it can be described by using the word “dilute” for solutions having very small quantities of solute and the word “concentrated” for solutions having large quantities of solute. However, this kind of description is inadequate and leads to confusion. Therefore, quantitative description, which is more appropriate, is used. Quantitatively, the concentration of a solution refers to the amount of solute present in a given quantity of the solution or solvent. The concentration can be expressed as:
Mass percentage: It is the number of parts by mass of solute per 100 part by mass of solution.
$$masspercent{t}_{solute}=({\displaystyle \frac{mas{s}_{solute}}{mas{s}_{solute}+mas{s}_{solvent}}})\times 100$$
Volume percentage: It is the number of parts by volume of solute per 100 part by volume of solution.
$$Volumepercent{t}_{solute}=({\displaystyle \frac{Volum{e}_{solute}}{Volum{e}_{solute}+Volum{e}_{solvent}}})\times 100$$
Normality: It is the number of gram equivalent of the solute present per litre of the solution.
$$Normality={\displaystyle \frac{G-equivalen{t}_{solute}}{Volum{e}_{solution}(litre)}}$$
Molarity: It is the number of gram mole of the solute present per litre of the solution.
$$Molarity={\displaystyle \frac{Mole{s}_{solute}}{Volum{e}_{solution}(litre)}}$$
Molality: It is the number of gram mole of the solute present per 1000g (1kg) of the solvent.
$$Molality={\displaystyle \frac{mol{e}_{solute}}{Mas{s}_{solvent}(kg)}}$$
Parts per million(ppm): It is the number of parts by mass of solute per million part by mass of the solution. Mathematically,
$$Partspermillion(ppm)={\displaystyle \frac{Mas{s}_{solute}}{Mas{s}_{solution}}}\times {10}^6$$
Now in our question, we have been given 1 litre solution. So, using the above formula we have
$${\displaystyle \frac{mas{s}_{solute}}{1000mL}}\times {10}^6=1ppm$$

So, the mass of solute comes out to be 0.001g or 1mg. So, Concentration of 1ppm means that 1L solution contains 1 mg solute.

Note: Parts per million is a unit that is capable of measuring very small amounts of solute in a large solution. So, it is used to measure the amount of impurities in water, even for soil and sediments. It is also used in medicine.