3. Show your work and balance the reaction equation below that illustrates the r

Question

3. Show your work and balance the reaction equation below that illustrates the redox reaction that happens in this titration experiment. (4 points) 4. From the balanced equation above what is the ratio of moles Fe2 to the moles of MnO4 5. Using your answers to questions 1 and 4 above, calculate the moles of iron that must have reacted with Mn04 to reach the endpoint in each titration trial. 6. Lastly, calculate the concentration of the unknown iron solution for each trial by dividing the number of moles of iron (question 5) by the volume (in liters) of iron solution (see first row of data table). Note that the proper units of concentration are M or mol/L and should be reported with your number here.

Explanation / Answer

3.

MnO4- (aq) + Fe2+ (aq) + H+ (aq) ------------>   Mn2+ (aq) + Fe3+ (aq) + H2O (aq)

Now,

Oxidation Number of Mn in MnO4- is given as

x + 4 (-2) = -1 or x = +7

Oxidation number of Mn = +7 , Oxidation number of O = -2 and other Oxidation numbers of other species are the charges represented by it.

Now, Change in O.N of Mn from MnO4- to Mn2+ = 7 - 2 = + 5

Change in O.N of Fe = 2 -3 = -1

So,

Fe2+ -------> Fe3+ + e-        --------- (1)

Mn7+ + 5e- -------> Mn2+     -----------(2)

So 5 e- are balance by multiplying 1 st equation with 5

5 Fe2+ --------> 5 Fe3+

Now equation is

MnO4- + 5 Fe2++ H+ --------------> Mn2+ + 5 Fe3+ + H2O

We have to balance oxygen by adding H2O so we have to multiply H2O by 4

MnO4- + 5 Fe2+ + H+ ---------------> Mn2+ + 5 Fe3+ + 4 H2O

We have to balance Hydrogen by adding H+ so we multiply H+ by 8

MnO4- + 5 Fe2+ + 8 H+ --------------> Mn2+ + 5 Fe3+ + 4 H2O       

Now everything is balanced so final reaction is

MnO4- (aq) + 5 Fe2+ (aq) + 8 H+ (aq) --------------> Mn2+ (aq) + 5 Fe3+ (aq) + 4 H2O (aq)

4.

Ratio of moles of Fe2+ to moles of MnO4- = 5 / 1 = 5 : 1

5.

Moles of iron that must have reacted with MnO4- to reach end point in two trials are

Trial 1

moles of MnO4- = 4.47 x 10^-4 moles

moles of Fe2+ reacted = (moles of MnO4-) * 5                   [because ratio of moles of Fe2+ to MnO4- = 5/1]

moles of Fe2+ reacted = 5 * 4.47 x 10^-4 = 2.235 x 10^-3 moles

Trial 2

moles of Fe2+ reacted = 5 * 4.8 x 10^-4 = 2.4 x 10^-3 moles

6.

Volume of iron solution has not been provided you can just the value of volume in the formula provided below

Trial 1

Concentration of iron solution = 2.235 x 10^-3 mol / Volume of iron solution (in L)

Trial 2

Concentration of iron solution = 2.4 x 10^-3 mol / Volume of iron solution(in L)

You only have to put the value of volume of iron solution and you will get the concentration.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.