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“So spring. Oh 619 let s write down all our information. Ten milliliters of ethanol. Ethanol.
The density is zero point seven eight nine grams per milliliter. There s 100 of solution and the solution density is zero point nine eight two grams okay. So we ll just start to tackle some of these let s see what we got i want to know what s gonna be helpful if i know like the moles and mass of the solute. The moles and mass of the solvent.
All that sort of stuff that will help me do these calculations a little easier so what i m gonna do is just take this times. The density of ethanol and i ll give me the grams of ethanol that i m adding to solution. So yeah. I m not solving further to you know one of them at this moment.
I just kind of gave myself set up you don t have to do this. Way you can go ahead and straight tap or one of them if you re ready to do that that s. Fine so looks like 789. Grams.
And that s a second all..
So that s the grams of ethanol. We also say it s a hundred mils of solution. Let s multiply by the solution density to get the amount of. Solution so that s let s see 098.
Two grams per milliliter milliliters cancel. So we re left with ninety eight point two grams on the solution hole how would i find the solvent i m just gonna subtract those two to get the solvent solvent somebody would do that that d be great otherwise it s just i don t know what it is now i m just gonna somebody wants to follow me with calculator. We ll use numbers if not we ll just do it in general ninety point three one grams of solvent and i believe it says the solvents water so let s just say water so we don t get ourselves confused okay. So that s nice to have the moles of the the mass of each of those let s also find the moles of every single one so to do the moles you just say well seven point eight nine grams of ethanol.
Again. I haven t solved for anything yet. I m just finding some helpful information. I need the molar mass of ethanol and that will give me the moles.
So whatever that is that s a moles of ethanol somebody actually you could tell me what it is i m gonna do the same for water. Thereby calculated. 46. This one right here or the molar mass.
Or the answer okay well the point one seven one and then this one 9023..
One divided by these people okay good we expect there be more moles of water because that s your solvent solvent so it s bigger okay now let s find a couple things your mole fraction asked for the mole fraction of ethanol that s the moles of ethanol divided by the total moles. So. 0171 if we did our math right 171 50. Whatever that s the mole fraction.
According to this it s zero point zero three three zero. So got the mole fraction. We can find the also the mass percent would be easy to get right now remember these numbers. I ll be asking you for them a second okay to get the mass fraction or the mass.
Percent. That s the sum mass. Percent. Back.
100 times. The mass of the solute seven point eight nine grams. Divided by the total mass ninety eight point two grams. So this part is really easy once you have all your masses and your moles.
According to this..
It s 822 three your second volume percent. That s actually a very easy one volume percent is one hundred you take this volume of the solute in a question in fact that said. It was ten milliliters divided by the total volume is one hundred that s just going to be ten percent. Let s see what i didn t get yet molarity and molality.
So for the molarity that s the moles of the solute. So let s see where that number is here zero point one seven one of the ethanol that s it moles divided by the leaders of solution quickly. Yeah. Zero point.
One one hundred milliliters or zero. Point. One zero zero. Liters.
That turns out to be one point. Seven. One molar and then the last one left is mole al or molality. So that one is little m.
Is going to be the moles of the solute zero point one seven one defined by the kilograms of the solvent..
This divided by 100 zero point zero nine zero three two one kilograms and that s gonna be one point eight nine. Okay if i got everything right there. We go does that kind of make sense in this question. Yeah in this question.
You ve got one point. If you put that percent right now and for the let s see molarity right here. If you put that m. There that was one point naught.
This is one point so you just went down wrote the unit s you got five three points on this one yeah. Most people don t do that i have no idea why i give this question every year. I don t know why you get used to these almost every year. They re on phones and that s what it means they re equivalent yeah.
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