Calculation problem

1. Jan 26, 2005

danne89

Hi!
How many per cent of silicon is there in a silicate mineral, if 0.567 g during analysis gave 0.484 silicon oxide.

Gratefull,
Danne

2. Jan 26, 2005

Gokul43201

Staff Emeritus
danne,

We really can not help you unless you first make an attempt. What ideas do u have ?

3. Jan 27, 2005

danne89

Oh, I'm sorry. But I've not any cloue.

4. Jan 27, 2005

dextercioby

Okay.
$$percentage \ Si =\frac{m_{Si}}{m_{compound}}\cdot 100$$

Daniel.

5. Jan 27, 2005

Gokul43201

Staff Emeritus
Ask yourself : how much Si is there in SiO2 ?

6. Jan 27, 2005

danne89

Okej, I've: % Si = Si:Si02 * 100 = 2800:60 ~= 47%

So the weight information's only purpose is to trick you? :(

7. Jan 27, 2005

dextercioby

No,its purpose is to help answer the problem's question.Reread its text and see what it needs to be done.

Daniel.

8. Jan 27, 2005

danne89

(0.567 * Si * 100):(0.484 * Si02) = (56.7 * 28):(0.484 * 60) = 1588:29.04 ~= 55%
Sorry for the amount of numbers, I'm using log-table.

9. Jan 27, 2005

dextercioby

I'm sorry,u have no reason to applogize,even after coming up,again,with a wrong answer.

Daniel.

10. Jan 27, 2005

apchemstudent

What's the unit of .484 ? grams?

11. Jan 27, 2005

dextercioby

No,MeV/c^{2}... :tongue:

Daniel.

12. Jan 27, 2005

apchemstudent

alright... I don't get 40 % when i try this problem out.

SiO2 = total weight

SiO =.484 grams

O = Total weight - .484 + (weight of O inside Silicon oxide)

Well we know how much Oxygen is in there we can easily figure out the percentage of Si....

I don't get 40 %... I think you've mistaken SiO for SiO2 (silicon oxide not dioxide)

Last edited: Jan 27, 2005
13. Jan 27, 2005

dextercioby

Of course it's $SiO_{2}$.

Daniel.

P.S.Does Silicium form oxides at +2??My guess is "no"...

14. Jan 27, 2005

danne89

% Si = (0.567 * Si * 100):(0.484 * Si*Si02) = (56.7 * 28):(0.484 * (28 + 28 + 2 * 16)) = 1587.6:(0.484 * 88) = 42.59%

Yes!! At least my slow head isn't act as a fools mind.

Last edited: Jan 27, 2005
15. Jan 27, 2005

dextercioby

Explain that part:
$$(28+28+2*16)$$

Why on Earth did u add 28 TWICE???

Daniel.

P.S.Is it $$Si_{2}O_{2}$$ ??

16. Jan 27, 2005

danne89

I add the Si and Si02 together.
Edit: Which seems to be quite idiotic now...

Last edited: Jan 27, 2005
17. Jan 27, 2005

danne89

Can I have some more hint?

18. Jan 27, 2005

dextercioby

Why would you do that for???It's only SiO_{2} in the mineral.It has the molecular mass of 60 and it's content of Si is
$$\frac{28}{60}$$

Is that enough ?

Daniel.

19. Jan 27, 2005

danne89

No. I can't solve it.

20. Jan 27, 2005

dextercioby

Okay.Here goes:
28g Si---------------------------->60g SiO_{2}
x g Si------------------------------>0.484g SiO_{2}

Find "x" and then:

x g Si-------------------------->0.567g mineral
y g Si-------------------------->100g mineral