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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: luffy on March 14, 2011, 04:47:31 pm

Title: Gravimetric Analysis Question
Post by: luffy on March 14, 2011, 04:47:31 pm: Hi, guys:
When I did the question below, my answer was different to the one given in the textbook. I just wanted to know whether or not I was completing it correctly.

A 0.500 g sample of sodium sulfate (Na₂SO₄) and a 0.500g sample of aluminium sulfate (Al₂(SO₄)₃) were dissolved in a volume of water and excess barium chloride added to precipitate barium sulfate. What was the total mass of barium sulfate produced?

Thanks in advance.
Title: Re: Gravimetric Analysis Question
Post by: huaxiadragon on March 14, 2011, 06:17:04 pm: since you only want the answer.
I'm too lazy so here's my answer

m(BaSO4)=1.8445g

I'll post the method if you want them, just ask
Title: Re: Gravimetric Analysis Question
Post by: luffy on March 14, 2011, 06:40:41 pm: Quote from: huaxiadragon on March 14, 2011, 06:17:04 pm
since you only want the answer.
I'm too lazy so here's my answer

m(BaSO4)=1.8445g

I'll post the method if you want them, just ask

Could you please show me how to do it too? I must have made an error somewhere.

Thanks.
Title: Re: Gravimetric Analysis Question
Post by: nacho on March 14, 2011, 07:17:49 pm: I got 1.8445
$n(Na_2SO_4) = \frac{0.5}{142.06} = 0.00352 mol$
$m(SO_4) in sample = 0.00352 x 96.06 = 0.338097g$

$n(Al_2(SO_4)_3)) = 0.5/342.14 = 0.001461 mol$

$n(SO_4) in sample = 0.004384 mol$
$m(SO_4) in sample = 0.004384 x 96 = 0.421143g$

n(Ba) which reacted with Soldium sulfate = 0.00353 mol
therfore m(Ba) = 0.00352 x 137.3 = 0.455836g

n(Ba) which reacted with Aluminium sulfate = 0.004384 mol
therefore m(Ba) = 0.004384 x 137. 3 = 0.60192 g
add them altogether to find the mass of BaSO4 and you get 1.8445

Edit: ceebs applying latex, also, how do i insert spaces in my latex equations?
Double edit: Btw, i used an overly-complicated long way to do this, you should just work out the total moles of $SO_4$ then with that find the total mols of Barium, then find the mass of the precipitate. Sorry
Title: Re: Gravimetric Analysis Question
Post by: huaxiadragon on March 15, 2011, 07:29:34 pm: lol just google it.

But I think that's it. havent tested it yet though.

http://www.personal.ceu.hu/tex/spacebox.htm