### Preparing dilutions using a stock solution of known concentration.

Note that the concentrations of the solutions shown on the left are millimolar (mM). This means there would
be 6.023 x 10^{20} molecules of ONP if you had a liter of the stock solution

Todetermine the volume of 2.5 mM ONP stock solution to use to create the dilutions shown on the left, employ
the following formula:

## C_{s}V_{s}=C_{f}V_{f}

_{}

C_{s }= concentration of the stock solution
V_{s }= volume of the stock solution |
C_{f }= concentration of the final solution
V_{f }= volume of the final solution |

Begin by making a 0.225 mM ONP solution. Assume your final solution volume (V_{f} ) will be 10 ml. How
much 2.5 mM ONP stock is needed? How much buffer?

1. Solve the equationf for **V**_{s }. **Click here**
to check you formula.

2. Plug in the numerical values for the other variables. **Click
here** to check your calculation.

3. Determine how much buffer to add to get a final volume of 10 ml. **Click
here** to check your calculation.

To test your understanding of these calculations try calculating the amount of pH 7.7 buffer and 2.5 mM ONP
stock solution to use to make the 0.175, 0.124, 0.075, and 0.025 mM solutions. **Click
here **to test you calculations.

**Back to making standard curves.**