A 2.4 liter sample of an aqueous solution contains 0.012 milliliters of ammonia. What is the concentration of ammonia in the solution expressed as parts per billion?
Alright. Since we're dealing with volume here, that must mean we are dealing with parts per billion in terms of volume. So, we'd say here parts per billion would equal the milliliters of our solute divided by milliliters of our solution, which in this case is our sample, times 109.
Here we plug in 0.012 milliliters of our ammonia, which is our solute, divided by now we need to convert liters into milliliters. And remember that for every 1 liter, it's 103 milliliters. So here, that comes out to 2,400 milliliters, which is what we're going to place over here. And then times 109. When we do that, that's going to give me, as an answer, 5,000 parts per billion.
And out of the choices shown, option B will be the correct answer. So, B, 5000 parts per 1,000,000,000, will be the correct concentration of NH3 expressed in parts per billion.