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.
moles CoSO4 = 0.001694mg/ 155 g/mol
= 1*10^-6 mol
Moles EDTA = 1*10^-6mol/0.025L
= 0.000436 mol/L (in 25 mL)
This is where I got stuck.
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 have several issues with a).
That's 1.694 mg CoSO4; when you convert that to 0.001694 that is now g/mL and not mg. Second where you have 1*10^-6 mol you threw away the other 3 places. The 1.695 is to four places and you should have 4 places in the answer.
So 1.694E-3 g/mL x 25 mL x (1 mol/155.0g) = 2.732E-4 mols EDTA needed.
M = mols/L and L = mols/M =
2.732E-4/0.008640 = ?L and convert to mL if needed.
To calculate the volume of 0.008640 M EDTA needed to titrate a 25.00 ml aliquot of the CoSO4 solution, you have already determined the number of moles of CoSO4 present in the aliquot.
Now, you can use the stoichiometry of the reaction between CoSO4 and EDTA to determine the moles of EDTA needed to react with the CoSO4.
The balanced equation for the reaction is:
CoSO4 + EDTA -> Co(EDTA) + SO4
From the balanced equation, we can see that 1 mole of CoSO4 reacts with 1 mole of EDTA.
So, the moles of EDTA needed is also 1*10^-6 mol.
To calculate the volume of 0.008640 M EDTA solution required, you can use the formula:
Molarity = moles/volume
rearranging the formula:
volume = moles/Molarity
Plugging in the values, we have:
volume = (1*10^-6 mol) / (0.008640 mol/L)
volume = 1.16*10^-4 L
Since the given solution is in mL, we convert the volume to mL:
volume = 1.16*10^-4 L * 1000 mL/L
volume = 0.116 mL
Therefore, the volume of 0.008640 M EDTA solution needed to titrate a 25.00 mL aliquot of the CoSO4 solution is 0.116 mL.
For part b) - In order to determine the volume of 0.009450 M Zn2+ solution needed to titrate the excess EDTA after the addition of 50.00 mL of the EDTA solution to a 25.00 mL aliquot of the Co2+ solution, we need to consider the balanced equation between EDTA and Zn2+.
The balanced equation for the reaction between EDTA and Zn2+ is:
Zn2+ + EDTA -> Zn(EDTA)2-
From the balanced equation, we can see that 1 mole of Zn2+ reacts with 1 mole of EDTA.
We already determined that the moles of EDTA in the solution is 1*10^-6 mol.
Therefore, the moles of Zn2+ required is also 1*10^-6 mol.
To calculate the volume of 0.009450 M Zn2+ solution needed, we can use the same formula as before:
volume = moles/Molarity
volume = (1*10^-6 mol) / (0.009450 mol/L)
volume = 1.06*10^-4 L
Converting to mL:
volume = 1.06*10^-4 L * 1000 mL/L
volume = 0.106 mL
Therefore, the volume of 0.009450 M Zn2+ solution needed to titrate the excess EDTA after the addition of 50.00 mL of the EDTA solution to a 25.00 mL aliquot of the Co2+ solution is 0.106 mL.