To fill in the equation McVc=MdVd, you need to determine the values for each variable.
1. Mc: Mc represents the concentration of the original standard phosphate solution. In this case, the given concentration is (1.e-002M) potassium dihydrogen phosphate, KH2PO4. Therefore, Mc = 1.e-002 M.
2. Vc: Vc represents the volume of the concentrated standard phosphate solution transferred to the volumetric flask. According to the instructions, you need to pipet 0.50 mL of the standard phosphate solution into a 100 mL volumetric flask. Hence, Vc = 0.50 mL.
3. Md: Md represents the new diluted concentration. Since you are diluting the standard phosphate solution, the new concentration needs to be calculated. In this case, the diluted concentration will be the concentration of the original solution after dilution. So, Md will be the concentration you calculate using the dilution formula.
4. Vd: Vd represents the total volume of the diluted solution. In this case, you are adding the concentrated standard phosphate solution (Vc = 0.50 mL) to a 100 mL volumetric flask, and then diluting it with distilled water. Therefore, Vd will be the final volume of the solution in the volumetric flask, which is 100 mL.
To calculate Md, you can use the dilution formula:
McVc = MdVd
Using the values we found earlier:
(1.e-002 M)(0.50 mL) = Md(100 mL)
Solving for Md:
Md = (1.e-002 M)(0.50 mL) / (100 mL)
Simplifying the equation:
Md = 0.00005 M
Therefore, the new diluted concentration (Md) is 0.00005 M.