# Chemistry Calculation

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#1
Hi,

Could someone please help me with this calculation as I have no idea what to do. Basically I had 5g of a soil sample diluted with 50ml of acid. I then made a 1x10-2 dilution and found the metal concentration in this dilution was 100microM. How do I find what the metal concentration in the initial sample is.

Thanks
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6 years ago
#2
(Original post by 170194)
Hi,

Could someone please help me with this calculation as I have no idea what to do. Basically I had 5g of a soil sample diluted with 50ml of acid. I then made a 1x10-2 dilution and found the metal concentration in this dilution was 100microM. How do I find what the metal concentration in the initial sample is.

Thanks
You want to multiply the dilute concentration 100microM by the dilution factor 10^2 to give you the initial concentration. Do you understand why that is?

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#3
I understand that. But is there anything else I need to do after?
0
6 years ago
#4
(Original post by 170194)
I understand that. But is there anything else I need to do after?
That gives you the metal concentration in the initial dilution. I'm not sure if the question's asking for the concentration in the initial solution or the concentration in the soil sample.

If it's the former, then that's all you have to do. If it's the latter, then use the concentration (in moldm^-3) of metal in the 50ml of acid to find the no. of mols of metal in the solution. You know that this no. of mols was contained in the 5g soil sample. So you can work out a concentration of the metal in the soil in molg^-1.:
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#5
Thanks for your help. I still don't quite understand how you find the concentration of the metal in the soil? do you find moles using Moles=c*v/1000 and then divide this by 5 to find the number of moles per 1g?
0
6 years ago
#6
(Original post by 170194)
Thanks for your help. I still don't quite understand how you find the concentration of the metal in the soil? do you find moles using Moles=c*v/1000 and then divide this by 5 to find the number of moles per 1g?
That's exactly what you need to do

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