How would you dilute a 2 mg/mL NaCl stock standard to make 100 ml of a 50 mg/dl standard?

To dilute a 2 mg/mL NaCl stock standard to make 100 mL of a 50 mg/dL standard, you'll need to calculate the volume of the stock solution required and the volume of diluent (usually water) needed. Here's how to do it:

Step 1: Calculate the amount of NaCl needed.
To determine the amount of NaCl required in the final solution, you can use the formula:
Amount of solute = concentration × volume

In this case, the desired concentration is 50 mg/dL, and the desired volume is 100 mL. Therefore,
Amount of NaCl needed = 50 mg/dL × 100 mL = 5000 mg

Step 2: Calculate the volume of stock solution required.
To find the volume of the stock solution needed, use the formula:
Volume of stock solution = Amount of solute ÷ Concentration of stock solution

The amount of NaCl needed is 5000 mg (from Step 1), and the concentration of the stock solution is 2 mg/mL. Hence,
Volume of stock solution = 5000 mg ÷ 2 mg/mL = 2500 mL (or 2.5 mL)

Step 3: Calculate the volume of diluent (water) needed.
To find the volume of diluent required, subtract the volume of the stock solution from the desired final volume:
Volume of diluent = Desired final volume - Volume of stock solution

In this case, the desired final volume is 100 mL, and the volume of stock solution needed is 2.5 mL. Thus,
Volume of diluent = 100 mL - 2.5 mL = 97.5 mL

So, to dilute a 2 mg/mL NaCl stock standard to make 100 mL of a 50 mg/dL standard, you would mix 2.5 mL of the stock solution with 97.5 mL of water (or any diluent).