Phosphate standards used to generate the calibration curve are usually made by first preparing a stock solution of known concentration, then diluting it to the required concentration.

Question

Phosphate standards used to generate the calibration curve are usually made by first preparing a stock solution of known concentration, then diluting it to the required concentration.

First prepare a stock solution that is 1.00 x 10-2 M in phosphate ion. How many g of Na3PO4 would you add to a 50 mL volumetric flask to to prepare this solution?

Second, what is this concentration in ppm of phosphate?

Answer 1

How many moles do you need to prepare the stock solution? moles = M x L = 0.01M x 0.050 L = ??

Since 0.01M in PO4^-3 is the same as 0.01M in Na3PO4, moles Na3PO4 will be the same as moles PO4^-3.
Then moles = grams/molar mass. Solve for grams Na3PO4.

Answer 2

To find out how many grams of Na3PO4 to add to prepare a 1.00 x 10-2 M (mol/L) solution in a 50 mL volumetric flask, we need to use the formula:

Molarity (M) = (moles of solute) / (volume of solution in L)

First, let's convert the volume of the flask from mL to L:
50 mL = 50/1000 L = 0.05 L

Now we can rearrange the formula to find the moles of solute:
moles of solute = Molarity (M) * volume of solution (L)

moles of solute = 1.00 x 10-2 mol/L * 0.05 L = 5.00 x 10-4 mol

Since Na3PO4 has a molar mass of 163.94 g/mol (sodium phosphate), we can calculate the mass of Na3PO4 needed:
mass of Na3PO4 = moles of solute * molar mass

mass of Na3PO4 = 5.00 x 10-4 mol * 163.94 g/mol = 0.08197 g

Therefore, you would need to add approximately 0.08197 grams of Na3PO4 to a 50 mL volumetric flask to prepare a 1.00 x 10-2 M solution.

Now, let's calculate the concentration in parts per million (ppm) of phosphate:
ppm = (mass of solute / mass of solution) * 10^6

The mass of the solute (Na3PO4) is 0.08197 g, as calculated above.

Next, we need to calculate the mass of the solution. Since the volume of the solution is given as 50 mL, we need to convert it to grams using the density of water (which is approximately 1 g/mL):
mass of solution = volume of solution * density of water

mass of solution = 50 mL * 1 g/mL = 50 g

Now, we can find the concentration in ppm:
ppm = (0.08197 g / 50 g) * 10^6 = 1,639.4 ppm

Therefore, the concentration of phosphate in the solution is approximately 1,639.4 ppm.