2. A researcher is often required to prepare solutions in the lab. Typically, a lab provides a concentrated solution. This solution must be diluted to the proper concentration. Hydrochloric acid is a common stock solution that is typically purchased at 37.0% HCl concentration (density = 1.20 g/ml). You must make 100 ml of 0.25 M HCl to do a DNA extraction experiment. How much of the 37.0% HCl concentration stock do you need to prepare this solution?

The easy to do this is to determine the molarity of the concentration HCl. That's

1.20 g/mL x 1000 x 0.37 x (1 mol/36.5g) = approx 12 M but you should be more accurate than that. Then use c1v1 = c2v2
12*v1 = 0.25*100

Solve for v1. That will give you the amount of concd HCl to pipet into a 100 mL volumetric flask and make to volume.

2.055ml

To calculate the amount of 37.0% HCl concentration stock solution needed to prepare 100 ml of 0.25 M HCl solution, we can use the formula:

M1V1 = M2V2

Where:
M1 = concentration of the stock solution (37.0%)
V1 = volume of the stock solution needed
M2 = desired concentration of the final solution (0.25 M)
V2 = desired final volume of the solution (100 ml)

Let's calculate the amount of stock solution needed:

Step 1: Convert the desired final volume from milliliters (ml) to liters (L):
V2 = 100 ml = 0.1 L

Step 2: Plug in the values into the formula and solve for V1 (volume of the stock solution needed):
M1V1 = M2V2
(0.37)(V1) = (0.25)(0.1)
0.37V1 = 0.025
V1 = 0.025 / 0.37
V1 ≈ 0.068 L

Step 3: Convert the volume from liters (L) to milliliters (ml):
V1 = 0.068 L = 68 ml

Therefore, you need approximately 68 ml of the 37.0% HCl concentration stock solution to prepare 100 ml of 0.25 M HCl solution for your DNA extraction experiment.

To find out how much of the 37.0% HCl concentration stock solution you need to prepare a 100 ml of 0.25 M HCl solution, we need to use the concept of molarity and dilution calculations.

Molarity is a measure of the concentration of a solution, defined as moles of solute per liter of solution (M = mol/L). In this case, the desired concentration is 0.25 M.

First, let's calculate the number of moles of HCl needed for the desired solution:
Molarity = moles of solute / volume of solution (in liters)

Rearranging the equation, we can find the number of moles of solute:
moles of solute = Molarity * volume of solution (in liters)

Since we need to prepare 100 ml of the solution, we convert it to liters:
Volume of solution = 100 ml = 100/1000 L = 0.1 L

Now, we can calculate the number of moles of HCl needed:
moles of HCl = 0.25 M * 0.1 L = 0.025 moles

Next, we need to calculate the mass of the HCl required using its concentration and density. The concentration is given as 37.0% HCl, so it means that 37.0 grams of HCl are present in 100 ml of the solution.

Therefore, we can calculate the mass of HCl needed for our desired moles:
mass of HCl = moles of HCl * molar mass of HCl

The molar mass of HCl is the sum of the atomic masses of hydrogen (H) and chlorine (Cl):
molar mass of HCl = (1.01 g/mol) + (35.45 g/mol) = 36.46 g/mol

Substituting the values into the equation:
mass of HCl = 0.025 moles * 36.46 g/mol = 0.9115 g

Therefore, you need approximately 0.9115 grams of the 37.0% HCl concentration stock solution to prepare 100 ml of 0.25 M HCl solution for your experiment.