# 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