Question #7ba62

1 Answer
Nov 6, 2015

Answer:

#"355 mg"#

Explanation:

Parts per million, or ppm, are used when dealing with very small concentrations of solute.

In simple terms, a concentration of one ppm is equivalent to one part solute per #10^6# parts solvent.

#color(blue)("ppm" = "mass of solute"/"mass of solvent" xx 10^6)#

You can assume that one liter of rain water has a density of approximately #"1 g/cm"^3#. Keeping in mind that you have

#"1 L" = "1 dm"^3 = 10^3"cm"^3#

you can say that one liter of rain water will have a mass of

#1color(red)(cancel(color(black)("L"))) * "1 g"/(1color(red)(cancel(color(black)("cm"^3)))) * (10^3color(red)(cancel(color(black)("cm"^3))))/(1color(red)(cancel(color(black)("dm"^3)))) = 10^3"g"#

So, you know that if you take the ratio between the mass of the solute and the mass of the solvent, and multiply the result by #10^6#, you get the concentration in ppm.

#"ppm" = m_(CO_2)/m_"water" xx 10^6#

This means that the mass of the solute can be determined by rearranging the equation

#m_(CO_2) = ("ppm" xx m_"water")/10^6#

#m_(CO_2) = (355 * 10^3"g")/10^6 = 355 * 10^(-3)"g"#

If you want, you can express this value in miligrams

#m_(CO_2) = color(green)("355 mg")#