To make 10 mL of 25 mM sodium standard, what volume of 1 M NaCl stock should be used?

250 mL
2.5 mL
0.25 mL
0.5 mL
None of these
400 mL

1 answer

Hmmm. mM? is that milliMolar?

If so, you are diluting it 1/.025 times, or 40 times, so you need 1 part stock, 39 parts water.

1/40 th of 10 ml is 10ml/40= .25ml stock

check my thinking