Question

if 171g of sucrose is added to 500ml of water, what is the molarity?

Answer 1

I know that this is chem, but I still need help!! @agent0smith

Answer 2

find the molar mass of sucrose first. Convert grams sucrose into moles of sucrose, and ml into liters. Divide moles by liters

Answer 3

Ok.. Let me see, how do I find the molar mass again? Don't I do the atomic mass of the element time however many g/mol there are?

Answer 4

So in this case since sucrose is C12-H22-O11 I'd have to do the mass of carbon (12.0107) times 12 since there are 12 g/mol, right?

Answer 5

yes! and then 22(1.01) and 11(16)

Answer 6

Ok, and then after that, what would I do?

Answer 7

how would you convert from grams to moles?

Answer 8

you have the gram amount right now

Answer 9

I'm actually not too sure.. :/

Answer 10

Well, there is a formula \[grams = moles/molar mass\]

Answer 11

But I don't know if this is correct or not..

Answer 12

okay! then you're \[grams \times \frac{ 1 mole }{ molar mass \in grams }\]

Answer 13

Um.. Okay, I'm a bit confused

Answer 14

its moles times molar mass to get grams

Answer 15

the unit for molar mass is grams per mol

Answer 16

How do I know how many moles there are though?

Answer 17

you're going to solve for it since you know the molar mass (from the periodic table) and the grams (in problem)

Answer 18

Ok, so the grams are 171, right?

Answer 19

And then the molar mass would be the overall c12-h22-o11 thing right?

Answer 20

yes

Answer 21

ok, give me a second to solve

Answer 22

Ok I got 342.3484 for the molar mass, is this correct?

Answer 23

And then would I divide that number by 171?

Answer 24

342 is correct but you're dividing the grams by the molar mass, so (171/342)

Answer 25

that gives you moles
then divide by the liters

Answer 26

ok so .5?

Answer 27

thats .5 liters yes

Answer 28

Ok, and now how do I find the molarity? I know its something like grams/liters

Answer 29

But that's where I usually mess up

Answer 30

yes, M = mols/ liters
we know how to find molarity (171/342) and divide by the liters

Answer 31

Oh really? We use the 171/342 to find the molarity? And what about the 500ml? Is that number important?

Answer 32

the 171 grams/342 grams gives moles of solute, not molarity

Answer 33

Oh ok.. So it would be .5/500?

Answer 34

.5 liters is the volume

Answer 35

Since the moles of solute is .5

Answer 36

okay, but convert ml to liters

Answer 37

.5/.5

Answer 38

1

Answer 39

yes!

Answer 40

So the molarity is 1?

Answer 41

correct
unless ap chem is failing me

Answer 42

in which case, i am sorry
but im very sure 1 is correct

Answer 43

Ok, so you are sure that the given 500 ml isn't important?

Answer 44

it is important though, you just used it

Answer 45

I did? When.. Sorry it is late and my brain is barely functioning... lol

Answer 46

you used it for the denominator of mols / liters =M

Answer 47

Oh right, right! So the "scientific" answer would be \[1 * 10^-3\]

Answer 48

Because .5/500 is equal to that number

Answer 49

no, you need to convert that 500 on the bottom to liters

Answer 50

you had it right before, .5/.5 = 1

Answer 51

Oh right... Omg, I'm sorry for being soo slow! So the final FINAL answer would be 1, right?

Answer 52

Si!

Answer 53

Oh ok! Thank you so much for your help! I might call on you tomorrow too for another problem, I need some help on!!

Answer 54

I gave you a medal and a fan too!

Answer 55

aw thanks! good luck with that chem my friend!