00:01
Okay, so we're working with k -o -h, and its molar mass is 56 .11 grams per mole.
00:06
And in our first example, we have 1 .13 molar.
00:11
So we can say we have 1 .13 moles of k -o -h for every one liter of solution.
00:22
Let's go ahead and change moles to grams.
00:26
So 56 .11 gives us 63 .4 grams of our k -o -8.
00:36
So 1 liter of solution is the same as a hundred milliliters of solution and we've got a density.
00:45
So let's go ahead and change milliliters to grams.
00:50
And we'll see that we have 10, 20 grams of solution.
00:57
So if we subtract the grams of solution, if we take that and we subtract the grams of our cellute, we'll get the grams of our water.
01:10
956, which is our solvent, grams of h2o, which is 0 .9566 kilograms.
01:21
I think we have everything we need now to go ahead and fill in our missing pieces.
01:26
Morality is moles of solute over kilograms of water.
01:35
So we've got 1 .13 moles divided by 0 .956 kilograms.
01:48
So that gives us 1 .18 molal for our percent by mass.
02:00
That's grams of solute over grams of solution times 100.
02:12
So that'll be 63 .4 grams divided by the 1020 grams times 100.
02:23
And that will give us 6 .22%.
02:28
So in this example, we're given 30 grams.
02:32
30 % by mass.
02:35
So we could start with 30 grams of k -o -h for every 100 grams of solution, which would give us if we subtract 70 grams of our solvent, which is water.
02:53
Let's go ahead and change grams to moles here.
02:57
Using our molar mass, we'll get 0 .535 moles...