Prepare a solution of 0.01M NaCl in 250ml and dilute this solution up to 0.0025M.

Question

Molarity  related. 

Answer 1

0.01 M NaCl means 0.01 moles of NaCl in a total volume of 1 liter. Converting this to amount needed for 250 ml (0.025 L), you get...

0.01 mole/L x 0.25 L = 0.0025 moles of NaCl required.

Converting this to grams of NaCl, you get ...

0.0025 moles NaCl x 58.44 g/mole = 0.1461 grams

To prepare this and then dilute it to 0.0025 M, you would...

Weigh out 0.15 g (15 mg) NaCl and dissolve it in a total final volume of 250 ml to make 0.01 M. Then dilute this solution by a factor of 

0.01M/0.0025M = 4. So, depending on the volume of 0.0025 M NaCl desired, you could dilute 1 ml of original solution up to a final volume of 4 ml, or 10 ml up to a final volume of 40 ml, or 5 ml up to a final volume of 20 ml, etc.