Background: a 5.0 ml sample of a protein is in a solution of 0.5 M NaCl. This so

Question

Background: a 5.0 ml sample of a protein is in a solution of 0.5 M NaCl. This solution is placed in dialysis tubing to remove as much NaCl as possible. In                    theory, the final concentration of NaCl should be the same inside as outside of the dialusis tubing after equilibrium has been reached.                 

                    1a) If I were to put the dialysis tubing in 4.0 L of dH2O for 12hrs. What will the NaCl concentration be in mM?                 

                    1b) What would be the concentration of the NaCl be if I put the tube in 1.0 L od dH2O for 6.0 hrs. and then an additional 1.0 L of fresh dH2O for 6 hrs?

                    Any help would be gretaly appreciated

Explanation / Answer

Molar mass NaCl = 23+35.5 = 58.5g/mol
1M solution = 58.5g in 1 litre
1mM solution = 58.5/1000 = 0.0585g/litre
50mM = 50*0.0585 = 2.925g/litre

If mM is millimolar ie one thousandth mole per litre

1 mole is 23 + 35.5 = 58.5g

1 mM is 58.5 / 1000 g/l

50 mM is 50 x 58.5 / 1000 = 2.925 g/l

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