Easy Chem help

[andy456]

Yeah its from heinmann... I just couldn't figure it out...
I hate empirical formulas

[andy456]

Ok, so i would just like to know if my working out is right.

What mass of barium chloride will remain after a 15.0g sample of the hydrated salt BaCl2.2H2O is heated to drive off all the water.

n(BaCl2)= 15.0/208.246
           = 0.07203019506mol
n(BaCl2)/n(H2O)= 2/1
n(H2O)= 0.1440603901mol

m(H2O)= 0.1440603901 x 18.01534
          = 2.595296908g

15.0g-2.595296908g
= 12.4g

[xD_aQt]

I got 12.8 g

[andy456]

How'd you work it out then???

[S2paramore]

I agree with xD_aQt. Your working doesn't seem to be correct.

I think it should be:

M(BaCl2 . 2 H2O) = 208.226 + 36.04 = 244.266 g/mol
n(BaCl2 . 2H2O) = 15.0 / 244.266 = 0.0614 mol
n(BaCl2 . 2H2O)= n(BaCl2)= 0.0614 mol
Mass BaCl2 = 0.0614 x 208.226 = 12.8 g

[Edmund]

I think the equation should look like this:



And have the same working as S2paramore/xD_aQt

[andy456]

Alright, i got another one:

For a 0.20M solution of potassium sulfate, K2SO4, calculate the amount, in mole, of:
-Potassium ions
-Sulfate ions
-oxygen atoms

Any help would be great

[fady_22]

It doesn't give enough information, skip it (it doesn't give you the volume of solution!).

[cindyy]

how come it doesnt give the volume :S that is so weird ...

[cindyy]

i have the solutions in front of me now, and this is what is written in the solution:

a   n(K2SO4) = C × V = 0.20 × 0.250 = 0.050 mol
        n(K+) = 2 × n(K2SO4) = 2 × 0.050 = 0.10 mol
b   n(SO42-) = n(K2SO4) = 0.050 mol
c   n(S) = n(K2SO4) = 0.050 mol


but doesnt give the volume in the Q

[andy456]

I hate my textbook... Thats like the 5th mistake so far.....
Thanks for your help though guys

[cindyy]

yeah i am using heinmann as well! but i actually quite like it, and i havent found any mistakes so far :S

[andy456]

Where did you get the solutions from???

[superflya]

yeah i am using heinmann as well! but i actually quite like it, and i havent found any mistakes so far :S

there a quite a few questions in the heinemann book with dodgy wording.

Where did you get the solutions from???

look around they were posted up a while back, use the search tool at the top right of ur window.

[cindyy]

ill give you solutions for chapter 3, your doing that now right?