AP Chemistry 3.2 Structure and Arrangement of Atoms
AP Chemistry 3.2 Structure and Arrangement of Atoms. What is the mole fraction of the solvent?
|AP Chemistry||Rearrangement and Reorganization of Atoms|
Structure and Arrangement of Atoms
|Test Prep||AP Chemistry|
mol of water (solvent).
What is the mole fraction of the solvent?
Here are the potential answers.. lot of numbers..
In order to satisfy Fergie’s craving, we're going to have to find some black eyed peas… [Black eyed peas stirring lemonade]
But if you just don't have those on hand, math will work just fine, too.
The question is asking us what mole fraction the solvent is.
So it might be helpful to know what mole fractions and solvents are before we dive in. [Lots of moles in the ground]
Well, the question conveniently tells us the solvent is water. [A girl drinking from a bottle of water]
If only all things in the wonderful world of AP-land were so easy…
And mole fraction doesn't refer to the unfortunate outcome of moles in The Texas Chainsaw Massacre… [A theatre showing the Texas Chainsaw Massacre on screen]
What the question actually means by mole fraction is simply what fraction of the total stuff
is the particular stuff we care about.
Kind of like if we were at a buffet that only offered two options: chocolate, [People holding plates at a buffet]
or asparagus-wrapped eggplant.
So what fraction of the buffet do we care about, or, what fraction of the buffet is
Also, where do we find a better buffet…?
Okay, back to the question…how much total stuff do we have? [Person sitting with feet up watching hoarders on TV]
Well, we have one mole of water and half a mole of sugar, so that gives us 1.50 total
moles of things in the mixture.
Since the question conveniently told us that the water is the solvent, we know that’s [A glass filling with water]
what we need to know the fraction of.
Now comes the scary part…
We're talking math.
But don't worry, it’s not that terrifying. [A kitten sat with a calculator]
All we have to do is divide the moles of the solvent by the total moles in the mixture.
We take 1.00 moles and divide it by 1.50 moles to give a mole fraction of 0.6666666666….
and let’s just round that to 0.667.
That means the answer is B.
But just for kicks and giggles, let's check out the rest of the answers. [Guy kicks friend in his leg]
Sounds almost as fun as chowing down at the chocolate, asparagus, eggplant buffet. [Man eating at a buffet and face turns green]
Since a mole fraction is some fraction of the total, it can’t be bigger than 1, which
rules out answer A.
Answer D, 0.500, says that half of the mixture would be water, which means there would be [A glass of water and a pile of sugar]
equal amounts water and sugar.
But if we look at the amounts we're given, 1 mole is more than 0.5 moles, so the fraction
should indicate that there is more water than there is sugar.
Answer D is out.
Similarly, answer C, 0.333, says that there is less water than sugar, which is also wrong.
Which leaves us with answer B again.
Phew. [Girl standing at a lemonade stand]
Time to wash that answer down with some refreshing lemonade and….
All we have is eggplant and asparagus. [Eggplant and asparagus appear on a table of lemonade]
Seriously people, we need a new buffet around here c'mon.