A solution contains 1.694 mg of CoSO4 (MW 155.0) per mL. Calculate

a) The volume of 0.008640 M EDTA needed to titrate a 25.00 ml aliquot of this solution.

Step 1. 0.001694g * 25ml * 1/155 g/mol= 0.0002732 mol

Step 2. Volume of EDTA needed = 0.0002732 mol/ 0.008640 M = 0.03125 or 31.25 mL

Having trouble with the next section.

b)The volume of 0.009450 M Zn2+ solution needed to titrate the excess reagent after the addition of 50.00 mL of the EDTA solution to a 25.00 mL aliquot of the Co2+ solution.

I posted earlier how to solve this problem (the b part). Show your work

To find the volume of the Zn2+ solution needed to titrate the excess reagent after the addition of the EDTA solution, we need to determine how much of the excess Co2+ remains.

Step 3. The molarity of Co2+ in the 25.00 mL aliquot can be calculated as follows:
- Moles of Co2+ = 0.001694 g * 1 mol/155 g = 0.00001094 mol
- Volume of Co2+ solution in the 25.00 mL aliquot = 0.02500 L or 25.00 mL
- Molarity of Co2+ = Moles of Co2+ / Volume of Co2+ solution = 0.00001094 mol / 0.02500 L = 0.000438 M

Step 4. Since the stoichiometric ratio between Co2+ and Zn2+ is 1:1, the number of moles of Zn2+ needed to react with the excess Co2+ present in the EDTA solution is equal to the number of moles of Co2+ in the aliquot (0.00001094 mol).

Step 5. To determine the volume of the 0.009450 M Zn2+ solution needed, we can rearrange the equation for molarity:
- Molarity of Zn2+ = Moles of Zn2+ / Volume of Zn2+ solution
- Volume of Zn2+ solution = Moles of Zn2+ / Molarity of Zn2+ = 0.00001094 mol / 0.009450 M = 0.001157 L or 1.157 mL

Thus, the volume of the 0.009450 M Zn2+ solution needed to titrate the excess reagent after the addition of the EDTA solution is 1.157 mL.

To calculate the volume of 0.009450 M Zn2+ solution needed to titrate the excess reagent after the addition of 50.00 mL of the EDTA solution to a 25.00 mL aliquot of the Co2+ solution, you need to follow these steps:

Step 1: Calculate the number of moles of EDTA in the 50.00 mL aliquot.

The number of moles of EDTA can be calculated using the formula:
Moles = Concentration × Volume

Moles of EDTA = 0.008640 M × 50.00 mL = 0.432 moles

Step 2: Calculate the number of moles of Zn2+ that can be chelated by the moles of EDTA.

Since the stoichiometric ratio between Zn2+ and EDTA is 1:1, the number of moles of Zn2+ that can be chelated is the same as the number of moles of EDTA.

Moles of Zn2+ = 0.432 moles

Step 3: Calculate the volume of 0.009450M Zn2+ solution needed.

The number of moles of Zn2+ can be calculated using the formula:
Moles = Concentration × Volume

0.432 moles = 0.009450 M × Volume

Solving for Volume:
Volume = 0.432 moles / 0.009450 M = 45.82 mL

Therefore, the volume of 0.009450 M Zn2+ solution needed to titrate the excess reagent after the addition of 50.00 mL of the EDTA solution is approximately 45.82 mL.