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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: gggggggggg on March 01, 2010, 03:51:16 PM

Title: Concentration Calculation which involves Unit Conversion!
Post by: gggggggggg on March 01, 2010, 03:51:16 PM

I have to change: mg/100ml  :rarrow: μg/ml and then to  :rarrow: mmole/litre.

So my value is 0.00303 mg/100ml.

My method: 1mg/100ml  :rarrow: 0.01mg/ml  :rarrow: 10μg/ml .    So 1 μg/ml = 0.001 mg/ml

0.00303/0.001 = 3.0320 μg/ml

Then we do number of moles= weight/ Molecular weight(112.1126). Thus we do 3.30320/112.1126 = 0.027044 μmole/ml

Then we do 0.027044 μmole/ml X 1000 to get 27.04495 mmole/Litre.


Is this right? Somehow i feel the final value is a way off for a concentration value. Is it that i needlessly multiplied the μmole/ml by 1000? Any help would be appreciated. Thank you.


S.T.J

Title: Re: Concentration Calculation which involves Unit Conversion!
Post by: sjb on March 02, 2010, 02:06:22 AM

Quote from: gggggggggg on March 01, 2010, 03:51:16 PM

I have to change: mg/100ml  :rarrow: μg/ml and then to  :rarrow: mmole/litre.

So my value is 0.00303 mg/100ml.

My method: 1mg/100ml  :rarrow: 0.01mg/ml  :rarrow: 10μg/ml .    So 1 μg/ml = 0.001 mg/ml

0.00303/0.001 = 3.0320 μg/ml

Then we do number of moles= weight/ Molecular weight(112.1126). Thus we do 3.30320/112.1126 = 0.027044 μmole/ml

Then we do 0.027044 μmole/ml X 1000 to get 27.04495 mmole/Litre.


Is this right? Somehow i feel the final value is a way off for a concentration value. Is it that i needlessly multiplied the μmole/ml by 1000? Any help would be appreciated. Thank you.


S.T.J

μmole / ml == 10^-6 mol / 10 ^-3 litre == 10^-3 mol / litre == mmol / litre

Title: Re: Concentration Calculation which involves Unit Conversion!
Post by: gggggggggg on March 02, 2010, 07:23:15 AM

Quote from: sjb on March 02, 2010, 02:06:22 AM

Quote from: gggggggggg on March 01, 2010, 03:51:16 PM

I have to change: mg/100ml  :rarrow: μg/ml and then to  :rarrow: mmole/litre.

So my value is 0.00303 mg/100ml.

My method: 1mg/100ml  :rarrow: 0.01mg/ml  :rarrow: 10μg/ml .    So 1 μg/ml = 0.001 mg/ml

0.00303/0.001 = 3.0320 μg/ml

Then we do number of moles= weight/ Molecular weight(112.1126). Thus we do 3.30320/112.1126 = 0.027044 μmole/ml

Then we do 0.027044 μmole/ml X 1000 to get 27.04495 mmole/Litre.


Is this right? Somehow i feel the final value is a way off for a concentration value. Is it that i needlessly multiplied the μmole/ml by 1000? Any help would be appreciated. Thank you.


S.T.J

μmole / ml == 10^-6 mol / 10 ^-3 litre == 10^-3 mol / litre == mmol / litre

Thanks for the response m8.

1)But was i right up to the point of getting 0.027044 μmole/ml.
2) So what you are saying is that i have to do 0.027044  X (10^-3) to get  mmol / litre?

Title: Re: Concentration Calculation which involves Unit Conversion!
Post by: sjb on March 02, 2010, 01:01:25 PM

Quote from: gggggggggg on March 02, 2010, 07:23:15 AM

Thanks for the response m8.

1)But was i right up to the point of getting 0.027044 μmole/ml.
2) So what you are saying is that i have to do 0.027044  X (10^-3) to get  mmol / litre?

I have not checked your maths, but no. If you have a solution that is x μmole/ml, then it is also x mmol/L (both quantity and volume are multiplied by 1000, so this cancels).

Title: Re: Concentration Calculation which involves Unit Conversion!
Post by: gggggggggg on March 02, 2010, 01:11:59 PM

Quote from: sjb on March 02, 2010, 01:01:25 PM

Quote from: gggggggggg on March 02, 2010, 07:23:15 AM

Thanks for the response m8.

1)But was i right up to the point of getting 0.027044 μmole/ml.
2) So what you are saying is that i have to do 0.027044  X (10^-3) to get  mmol / litre?

I have not checked your maths, but no. If you have a solution that is x μmole/ml, then it is also x mmol/L (both quantity and volume are multiplied by 1000, so this cancels).

I understand that part now. But lets ignore the math...The method up until getting to the μmole/ml value was correct no?

Title: Re: Concentration Calculation which involves Unit Conversion!
Post by: sjb on March 02, 2010, 04:18:15 PM

I assume so. I don't know where you got "0.00303/0.001 = 3.0320 μg/ml" from, though