# Redox Titration help

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#1
If anyone could please help me with these questions on a redox titration involving potassium permanganate and potassium oxalate, it would be greatly. appreciated.

1st titration:
Primary standard =0.05M K2(C2O4).H2O (250 ml)
10 ml of primary standard into conical flask, sulfuric acid added and heated. KMnO4 titrated against the oxalate solution.
volume of KMnO4 needed to reach endpoint of titration = 10.03 ml

1) Calculate how many moles of K2(C2O4).H2O are present in 2.3 g.
Molecular mass of K2(C2O4).H2O = 184 g2.3 g/184 g = 0.0125 mol
2) Calculate the molar concentration of the K2(C2O4).H2O standard solution you prepared.
0.0125 mol/0.25 L = 0.05 M
3) Calculate how many moles of K2(C2O4).H2O are present in 10 mL of the standard solution you prepared.
0.05 moles in 1000 mL0.05 moles/100 in 1000 mL/1000.0005 moles in 10 mL

1) Write out the balanced equation showing what happens to K2(C2O4).H2O upon addition of H2SO4 and heating.
K2(C2O4) + H2SO4 → H2C2O4 + K2SO4Oxalate reacts very slowly at room temperature so the solutions are titrated hot to make the procedure practical.
2) Write a balanced equation and indicate the ratio for the reaction of (COOH)2 with KMnO4.
5 (COOH)2 + 2 KMnO4 + 3 H2SO4 = 10 CO2 + 2 MnSO4 + K2SO4 + 8 H2O 5 : 2 : 3 : 10 : 2 : 1 : 8
4) Calculate how many moles of KMnO4 are present in the average volume at the end-point.
5 x 10^-4/5 moles x 2 = 2 x10^-4

5) Calculate the molar concentration of the KMnO4 solution used.
2 x 10-4/10.03 mL = 0.02 M
1) Calculate the concentration in grams per liter (g L-1) of the (COOH)2 xH2O solution you prepared.

2) What happens to (COOH)2 xH2O when it dissolves in water?

2nd titration:
Preparation of a solution of oxalic acid:
Volume needed to reach endpoint of titration = 10 ml

2) Calculate how many moles of KMnO4 are present in the average volume at the end-point.

3) Calculate how many moles of (COOH)2 are present in the 10 mL solution you pipetted in the conical flask.

4) Calculate the molar concentration of (COOH)2 in the solution used.

5) Convert the concentration of (COOH)2 from molarity (mol L-1) to grams per litre (g L-1).

6) The calculated concentration in grams per litre is less than that calculated in Part 3. The difference is due to the waters of crystallization. What was the mass of water per litre?

7) Use the molecular weight of H2O to determine the value of “x” in (COOH)2 xH2O.

0
5 years ago
#2
(Original post by elef95)
If anyone could please help me with these questions on a redox titration involving potassium permanganate and potassium oxalate, it would be greatly. appreciated.

1st titration:
Primary standard =0.05M K2(C2O4).H2O (250 ml)
10 ml of primary standard into conical flask, sulfuric acid added and heated. KMnO4 titrated against the oxalate solution.
volume of KMnO4 needed to reach endpoint of titration = 10.03 ml

1) Calculate how many moles of K2(C2O4).H2O are present in 2.3 g.
Molecular mass of K2(C2O4).H2O = 184 g2.3 g/184 g = 0.0125 mol 2) Calculate the molar concentration of the K2(C2O4).H2O standard solution you prepared.
0.0125 mol/0.25 L = 0.05 M 3) Calculate how many moles of K2(C2O4).H2O are present in 10 mL of the standard solution you prepared.
0.05 moles in 1000 mL0.05 moles/100 in 1000 mL/1000.0005 moles in 10 mL 1) Write out the balanced equation showing what happens to K2(C2O4).H2O upon addition of H2SO4 and heating.
K2(C2O4) + H2SO4 → H2C2O4 + K2SO4Oxalate reacts very slowly at room temperature so the solutions are titrated hot to make the procedure practical.
2) Write a balanced equation and indicate the ratio for the reaction of (COOH)2 with KMnO4.
5 (COOH)2 + 2 KMnO4 + 3 H2SO4 = 10 CO2 + 2 MnSO4 + K2SO4 + 8 H2O 5 : 2 : 3 : 10 : 2 : 1 : 8 4) Calculate how many moles of KMnO4 are present in the average volume at the end-point.
5 x 10^-4/5 moles x 2 = 2 x10^-4 5) Calculate the molar concentration of the KMnO4 solution used.
2 x 10-4/10.03 mL = 0.02 M 1) Calculate the concentration in grams per liter (g L-1) of the (COOH)2 xH2O solution you prepared.
You know the mass and volume of solution used, no? 2.3 g in 250ml

2) What happens to (COOH)2 xH2O when it dissolves in water?
It separates the oxalic acid from the water of crystallisation.

2nd titration:
Preparation of a solution of oxalic acid:
Volume needed to reach endpoint of titration = 10 ml

2) Calculate how many moles of KMnO4 are present in the average volume at the end-point.

3) Calculate how many moles of (COOH)2 are present in the 10 mL solution you pipetted in the conical flask.

4) Calculate the molar concentration of (COOH)2 in the solution used.

5) Convert the concentration of (COOH)2 from molarity (mol L-1) to grams per litre (g L-1).

6) The calculated concentration in grams per litre is less than that calculated in Part 3. The difference is due to the waters of crystallization. What was the mass of water per litre?

7) Use the molecular weight of H2O to determine the value of “x” in (COOH)2 xH2O.

The second question is pretty much the same as the first ...
0
#3
Calculate the concentration in grams per liter (g L-1) of the (COOH)2 xH2O solution you prepared:
Is it just 9.2 g/L?

When I'm calculating the molecular mass of (COOH)2 xH2O, do i just count the (COOH)2 since i dont know how much water molecules there are?
0
5 years ago
#4
(Original post by elef95)
Calculate the concentration in grams per liter (g L-1) of the (COOH)2 xH2O solution you prepared:
Is it just 9.2 g/L?

When I'm calculating the molecular mass of (COOH)2 xH2O, do i just count the (COOH)2 since i dont know how much water molecules there are?
a) yes
b) no
0
#5
Thank you.
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