00:01
In this problem, we're asked to find the mass percent of nacl in our diluted solution.
00:06
So the first question we have to ask ourselves is, what is mass percent? so mass percent is the mass of solute over the mass of solution multiplied by 100 percent.
00:17
So in our problem specifically, we know that our solute is nacl, and that our solution is some sort of mix between nacl plus water.
00:27
So let's see the information that we're given in this problem.
00:31
So we know that our original solution of nacl plus water weighed about 75 grams.
00:39
And then we added 500 grams of water onto that.
00:45
And so we then had a total of 575 grams in our total solution.
00:54
So now we have the bottom portion of this equation, but we still need to find the mass of our solute.
01:02
And so let's see what we're given in this problem.
01:04
So we know that this original solution has a molality of 2 .5.
01:10
So what does that mean? so molality is a number of moles of our solute over a certain amount of kilograms of solvent.
01:22
And so plugging in the information that we have, we know that the molality is 2 .5 % of our original solution.
01:29
We don't know the moles yet, but we know that the original solution had a mass of 75 grams, which is the equivalent of 0 .75 kilograms.
01:46
And here, solving for x, we get 0 .1875 moles of nacl...