Question

Hello, i had an experiment during my chemistry class, mixing HCl,BaCl2, and unknown sample.
it made a precipitation.

I need to find: 1) mass of sulfate in unknown sample 2) % of sulfate in unknown sample 3) identity of unknown sample Possible Cations: Na, K, Cd, or NH4
possible equation with +1 cation: BaCl2+M2SO4 -> BaSO4 + 2MCl
possible equation with +2 cation: BaCl2+ MSO4 -> BaSO4+ MCl2

Here are some data:
mass of unknown sample: 0.329g
mass of crucible: 10.990g
mass of crucible +BaSO4 : 11.532
mass of BaSO4: 0.542g

Answer 1

Ooh, I am not that into chemistry yet. I know @Mashy is a great chemist or physicist. I forgot, but I think she can help. c;

Answer 2

Sorry I could not 100% answer your question. Welcome to OpenStudy. :)

Answer 3

@kewlgeek555 Thank you though :)

Answer 4

a) i am a HE
b) I m into physics.. not chemistry :P
@kewlgeek555

Answer 5

You have the mass of BaSO_4 and you know that for each barium molecule there is one sulfate molecule (in a 1:1 ratio)

Answer 6

So if you calculate the molecular mass (A_r) of BaSO_4 then you can calculate the number of moles of BaSO_4, since they're in 1:1 for every mole of BaSO_4 there is that same amount of Ba^2+ and that same amount again of SO4^2-
Then just back calculate to find how much sulfate is in the unknown

Answer 7

@Silent_Sorrow Thank you for your help, so i got 0.00232 mol SO4. I'm stuck with how to find sulfate in the unknown

Answer 8

So go mass(unkown) - mass(sulfate in unkown) = mass(cation in unknown)
then go mass(cation in unknown)/amount(sulfate) which will give you a molar mass, then match it to one of the cations

Answer 9

how do you find mass of sulfate in unknown?

Answer 10

the amount (of moles) of sulfate for BaSO_4 is the same as in the unknown
This makes the assumption that the unknown was the only possible source of sulfate ions.

Answer 11

Also when you find the molar mass for the unknown cation I just mentioned, if none of them have that molar mass, try dividing the calculated one by two which will give you the molar mass for a 1+ cation.

Answer 12

okay, so i got 0.106g of mass of cation in unknown. and like you mentioned,
0.106g (mass of cation) / 0.00232mol (moles of sulfate) = 45.699 which does not match with any of it. so i divide that by 2 gives me 22.845 which is close to Na.

Answer 13

@Silent_Sorrow Am i on right track?

Answer 14

Yup, that's the exact answer I got!

Answer 15

@Silent_Sorrow jesus christ you're my live savior !!!!!!!!!!!!! seriously!!! this report was due tmrw and i was very close to give up but you saved me and my grade !!! Thank you so much :D

Answer 16

life*

Answer 17

You're most welcome, I remember doing that experiment at school :)

Answer 18

@Silent_Sorrow :D hopefully see you around when im lost again hehe
you're the best!