In this lesson, we’ll learn the difference between parts per million and parts per billion.
Parts per million, which is abbreviated ppm, represents the mass of our solute which is a smaller portion of our solution divided by the mass of solution multiplied 106.
Here, in this example we have 12.5 grams of carbon dioxide dissolved in 1750 g of water. This is the smaller amount, so this represents our solute. This is our much greater amount so this represents our solvent. Remember, your solution is your solute plus your solvent together. Once we plug this in, we’ll put the grams of solute on top divided by grams of solute plus grams of solvent on the bottom times 106. This gives us our parts per million of 7092.2 parts per million.
When it comes to parts per billion, which is abbreviated ppb, that’s almost the same exact formula. It’s still mass of solute divided by mass of solution. But because we’re dealing with billions here, it’d now be times 109. We’re going to say here we’re dealing with the same exact numbers, so our solute is still the carbon dioxide and our solvent is still the water. We plug in the same numbers but now we multiply it by 109 because again, we’re dealing with billions. In this case, it gives us 7.0922 x 106 parts per billion.
Just remember, there’s similarities between both of these terms. Parts per million deals with 106whereas parts per billion deals with 109.