# Concenctration of a mass

1. Dec 6, 2009

### Kelly09

Hi guys,here is my question. What is the Concentration of Na2CO3 when it dissolves in a solution and forms a volume of 100 cubic cm?

Concentration= moles/volume.
I found moles using mass/atomic mass of Na2+C+03.
Then i used moles/volume to calculate concentration. Correct?

2. Dec 6, 2009

### Kelly09

Mass of Na2CO3 is 5.8g

3. Dec 6, 2009

### sjb-2812

So far so good.

4. Dec 6, 2009

### Kelly09

I found concentration to be 0.0005M. Could you confirm if this is correct?

5. Dec 6, 2009

### sjb-2812

Sounds a bit low to me, can you show your working?

6. Dec 6, 2009

### Kelly09

Concentration=moles/volume

Moles = mass/atomic mass, 5.8g/Na2C03

So 5.8/106=0.005moles.

Conc=0.05/100=0.0005M. So?

7. Dec 6, 2009

### sjb-2812

What is the definition of M here?

8. Dec 6, 2009

### Kelly09

M is concentration. There are two ways of writing it,M or mol/dm3

9. Dec 6, 2009

### sjb-2812

OK, so how many dm3 are there in your solution?

10. Dec 6, 2009

### Kelly09

0.0005mol/dm3

11. Dec 6, 2009

### Char. Limit

No... what you'd get in your calculations is 0.0005 mol/cm^3. You should change your mL (cm^3) to L (dm^3) before using it.

12. Dec 7, 2009

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