Syllabus Question G13

[Kaija Frassrand 2F]

I understand the rest of the answer to the problem, but where did 0.050 M come from in the concentration of diluted NH4NO3 solution? I can't figure out how the word problem was manipulated to come up with that.

[Timothy Li 3A]

.20 M represents .2 mols per 1 liter. However, when we add 3.0 more liters, our molarity must change because now we have a total of 4 liters and the original solution is diluted. We would thus divide the original .20 mols by 4 liters to get .050 M or .050 moles per 1 liter.