What weights of.....?

Question

What weights of Bovine Serum Albumin (molecular weight 66,000) are required to give solutions of 10ml and 100ml volumes containing 1μmole of BSA?

dont kno where to start.....how do i calculate

Answer 1

Suspected trick question. The volumes included are irrelevant. You know the molecular weight (66000 Da) and you know how many micromoles you need total in each solution. What does it matter if the one micromole is in 1 ml or 10K gallons? You know it only contains one micromole. Divide the molecular weight by 10^6 and you're done. (or you have not stated the problem correctly)

Answer 2

To answer your question in the way you asked it:
A micromole is an amount and so there is the same amount of albumin in each.
1 micromole of albumin is the molecular weight divided by a million = 0.066g. This is dissolved in 10ml for the first solution and the same amount dissolved in 100ml for the second.

In practice, for accuracy, you would dissolve 6.6g in 1 litre for the first solution and take 100ml of this solution and dilute it to 1 litre for the second.

Answer 3

The volumes do matter if you are asked for the final molarity - are you? You are asked to make a solution where 1μmole is contained in 10ml and another where 1μmole is contained in 100ml, so their molarities are different.

In each case you need 66000/1000000g of substance, as the previous answer said, but in one case you dissolve it in 10ml and the other you dissolve it in 100ml. Are you sure the question doesn't ask you for the final molarity? If so, convert your weight to be how much would be in 1l instead of the volumes you are given.

Answer 4

Do you mean 1 umole or 1 uM (one is an amount the other a concentration).

If you are looking for the amount then moles = Mass / MWt. So Mass= moles x MWt. (1 umole = 10-6 M)

If you want the concentration then conc = moles / volume (in dm3) (don't forget 1 dm3 = 1000ml)

so you work out the number of moles = 1 uM X vol
then mass = moles x Mwt.