Question

The concentration of a solution of iron(II) sulfate, FeSO4, can be determined through a redox titration. A 50.00 mL sample of the solution is diluted to 250.00 mL with deionized water. A 25.00 mL aliquot is then pipetted into an Erlenmeyer where it is acidified with sulfuric acid and then titrated with a standard solution of potassium dichromate, K2Cr2O7. The reactants and products of the reaction (unbalanced) are as follows: Cr2O7^2- (aq) + Fe^2+ (aq) ? Cr^3+ (aq) + Fe^3+ (aq) a) Write the balanced half-reactions (be sure to indicate which is the oxidation and which is the reduction half-reaction), as well as the overall balanced redox equation for the reaction between the dichromate ion and iron(II) ion in acidic solution. b) Using the data provided here (and above), calculate the molarity of the original iron sulfate solution. Show your reasoning/calculations. Volume of original sample 50.00 mL Volume of diluted solution 250.00 mL Volume of diluted sample titrated 25.00 mL Standard dichromate solution, [Cr2O7^2-] 0.04353 M Initial burette reading 0.24 mL Final burette reading 23.60 mL

          The concentration of a solution of iron(II) sulfate, FeSO4, can be determined through a redox titration. A 50.00 mL sample of the solution is diluted to 250.00 mL with deionized water. A 25.00 mL aliquot is then pipetted into an Erlenmeyer where it is acidified with sulfuric acid and then titrated with a standard solution of potassium dichromate, K2Cr2O7. The reactants and products of the reaction (unbalanced) are as follows:

Cr2O7^2- (aq) + Fe^2+ (aq) ? Cr^3+ (aq) + Fe^3+ (aq)

a) Write the balanced half-reactions (be sure to indicate which is the oxidation and which is the reduction half-reaction), as well as the overall balanced redox equation for the reaction between the dichromate ion and iron(II) ion in acidic solution.

b) Using the data provided here (and above), calculate the molarity of the original iron sulfate solution. Show your reasoning/calculations.

Volume of original sample 50.00 mL
Volume of diluted solution 250.00 mL
Volume of diluted sample titrated 25.00 mL
Standard dichromate solution, [Cr2O7^2-] 0.04353 M
Initial burette reading 0.24 mL
Final burette reading 23.60 mL

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The concentration of a solution of iron(II) sulfate, FeSO4, can be determined through a redox titration. A 50.00 mL sample of the solution is diluted to 250.00 mL with deionized water. A 25.00 mL aliquot is then pipetted into an Erlenmeyer where it is acidified with sulfuric acid and then titrated with a standard solution of potassium dichromate, K2Cr2O7. The reactants and products of the reaction (unbalanced) are as follows:

Cr2O7^2- (aq) + Fe^2+ (aq) ? Cr^3+ (aq) + Fe^3+ (aq)

a) Write the balanced half-reactions (be sure to indicate which is the oxidation and which is the reduction half-reaction), as well as the overall balanced redox equation for the reaction between the dichromate ion and iron(II) ion in acidic solution.

b) Using the data provided here (and above), calculate the molarity of the original iron sulfate solution. Show your reasoning/calculations.

Volume of original sample 50.00 mL
Volume of diluted solution 250.00 mL
Volume of diluted sample titrated 25.00 mL
Standard dichromate solution, [Cr2O7^2-] 0.04353 M
Initial burette reading 0.24 mL
Final burette reading 23.60 mL

Added by Tiffany H.

Chemistry: Structure and Properties

Nivaldo Tro 2nd Edition

Instant Answer

Solved by Expert Ivan Kochetkov

01/17/2022

Step 1

Reduction half-reaction: Cr2O7^2- (aq) + 14H+ (aq) + 6e- -> 2Cr^3+ (aq) + 7H2O (l) Oxidation half-reaction: Fe^2+ (aq) -> Fe^3+ (aq) + e- Overall balanced redox equation: 6Fe^2+ (aq) + Cr2O7^2- (aq) + 14H+ (aq) -> 6Fe^3+ (aq) + 2Cr^3+ (aq) + 7H2O (l) Show more…

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The concentration of a solution of iron(II) sulfate, FeSO4, can be determined through a redox titration. A 50.00 mL sample of the solution is diluted to 250.00 mL with deionized water. A 25.00 mL aliquot is then pipetted into an Erlenmeyer where it is acidified with sulfuric acid and then titrated with a standard solution of potassium dichromate, K2Cr2O7. The reactants and products of the reaction (unbalanced) are as follows: Cr2O7^2- (aq) + Fe^2+ (aq) → Cr^3+ (aq) + Fe^3+ (aq) a) Write the balanced half-reactions (be sure to indicate which is the oxidation and which is the reduction half-reaction), as well as the overall balanced redox equation for the reaction between the dichromate ion and iron(II) ion in acidic solution. b) Using the data provided here (and above), calculate the molarity of the original iron sulfate solution. Show your reasoning/calculations. Volume of original sample: 50.00 mL Volume of diluted solution: 250.00 mL Volume of diluted sample titrated: 25.00 mL Standard dichromate solution, [Cr2O7^2-]: 0.04353 M Initial burette reading: 0.24 mL Final burette reading: 23.60 mL

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Transcript

00:01 Here we have to solve the given problem.

00:02 First we have to balance right balance half reactions.

00:10 So let's start with the reduction reaction.

00:15 Let's do it here.

00:16 So in the reduction reaction, bichromate is reduced to chromium 3 plus.

00:41 This reaction takes place in the acetic media.

00:44 That's why we add seven molecules of water to the right and 14 protons to the left.

00:52 Additionally we have to balance the charge that's why we add six electrons.

01:02 Oh so we first have to balance chromium.

01:06 Now there is same amount of chromium on each side and same amount of hydrogen and oxygen.

01:14 So we just need to balance up church.

01:18 To balance the church to make it six plus on the left we have to add six electrons.

01:26 So now let's write down the oxidation half reaction.

01:34 And oxidation, the oxidation half reaction is a formation of iron 3 plus from iron 2 plus.

01:44 So iron 2 plus loses an electron and forms iron 3 plus.

01:52 So overall that is a 6 electron reaction, so we multiply the first half reaction by 1 and the second by 6.

02:03 So now let's write down the total reaction below.

02:07 So this is bichromate plus 14 h plus plus plus 6 iron 2 plus forming 2 chromium 3 plus plus 6 iron 3 plus and plus 7 molecules of water.

02:45 Now let's see if the charge is balanced.

02:49 So 18 plus on each side here, everything is balanced.

02:55 Okay, now we here we have to calculate the malaria of the original iron sulfate solution.

03:06 So we need to know the concentration of this original iron sulfate solution...

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