You need 3.5L of 50mM NaCl from your 20X stock. How would you accomplish this:

20X stock __________ml
Pure Water ___________ml

From whatever number I plugged in trying to solve it, I got: 175ml of 20X stock and 3,430ml of Pure Water. Have no idea if those are right. Any help is appreciated.

I'm not sure either.

To prepare 3.5L of 50mM NaCl from your 20X stock solution, follow these steps:

Step 1: Determine the final volume of the solution.
- We want to prepare 3.5L (or 3500 ml) of the final solution.

Step 2: Calculate the volume of the 20X stock solution required.
- Since the stock solution is 20 times more concentrated than the desired final concentration, we need to dilute it.
- The formula to calculate the volume of stock solution required is:
Volume of stock solution = (Desired final volume / Stock solution dilution factor)
Volume of stock solution = (3500 ml / 20)
Volume of stock solution = 175 ml

Step 3: Calculate the volume of pure water required.
- To make up the rest of the final volume, we need to add pure water.
- The formula to calculate the volume of pure water required is:
Volume of pure water = Desired final volume - Volume of stock solution
Volume of pure water = (3500 ml - 175 ml)
Volume of pure water = 3325 ml

So, to prepare 3.5L of 50mM NaCl from your 20X stock solution, you will need:
- 175 ml of the 20X stock solution
- 3325 ml of pure water

To determine how much 20X stock and pure water you need, we can use the dilution equation:

(C1)(V1) = (C2)(V2)

Where:
C1 = Concentration of the stock solution (in this case, 20X)
V1 = Volume of the stock solution
C2 = Desired concentration of the diluted solution (in this case, 50mM)
V2 = Total volume of the diluted solution (including both the stock solution and pure water)

Let's solve the equation step by step:

1. Convert the concentration of the stock solution from 20X to molar concentration. To accomplish this, divide the stock concentration by the dilution factor. In this case, the dilution factor is 20.

20X stock concentration = 20 * C2
= 20 * 50 mM
= 1000 mM

2. Next, plug in the values into the dilution equation:

(1000 mM)(V1) = (50 mM)(3.5 L)

3. Rearrange the equation to solve for V1:

V1 = (50 mM)(3.5 L) / 1000 mM
= 1.75 L

So, you would need 1.75 L of the 20X stock solution.

To calculate the volume of pure water, subtract the volume of the stock solution from the total volume:

Volume of pure water = Total volume - Volume of stock solution
= 3.5 L - 1.75 L
= 1.75 L

Therefore, you would need 1.75 L of pure water.

Based on the calculations, your initial guess of 175 mL of 20X stock and 3,430 mL of pure water is not correct. Instead, you would need 1.75 L of the 20X stock solution and 1.75 L of pure water.