Answer the following question about BeC₂O₄(s) and its hydrate
A 0.345 g sample of anhydrous BeC₂O₄, which contains an inert impurity, was dissolved in sufficient water to produce 100.0 ml of solution. A 20.0 ml portion of the solution was titrated with KMnO₄(aq). The balanced equation for the reaction that occurred is as follows:

16 H⁺ (aq) + 2 MnO ₄ ^-(aq) + 5 C₂O₄ ^2- (aq)
→ 2 Mn²⁺(aq) + 10 CO₂(g) + 8 H₂O(l)
The volume of 0.0150 M KMnO₄(aq) required to reach the equivalence point was 17.80 ml.
(i) Identify the reducing agent in the titration reaction. (1 point)
(ii) For the titration at the equivalence point, calculate the number of moles of each of the
following that reacted. (2 points)
a) MnO₄^- (aq)
b) C₂O₄ ^2-(aq)

(iii) Calculate the total number of moles of C₂O₄ ^2- (aq) that were present in the 100.0 ml of prepared solution. (1 point)
(iv) Calculate the mass percent of BeC₂O₄(s) in the impure 0.345 g sample. (1 point)

What is your own work? Where do you have difficulties. You should Show your own Attempts before receiving help.

16 H⁺ (aq) + 2 MnO ₄ ^-(aq) + 5 C₂O₄ ^2- (aq)
→ 2 Mn²⁺(aq) + 10 CO₂(g) + 8 H₂O(l)

Oxidation reduction reaction -
Oxidation is loss of electrons so there is an increase in positive charge and decrease in negative charge when a species is undergoing oxidation.
Reduction is gain of electrons so there is decrease in positive charge or increase in negative charge  and it means species is reduced.

In this question we need to check the change in oxidation numbers -
If there is an increase in oxidation number then that species is oxidized.
If there is a decrease in oxidation number then that species is reduced.

Now  H⁺      →          H₂O is +1 on both sides.

Oxygen is -2 both sides because all these are oxides( oxalate , permanganate, carbon dioxide )  with an  oxidation number of -2.
                           
C₂O₄ ^2- (aq)          →                 CO₂(g)
In oxalate carbon O.N is +3                                                                             In carbon dioxide C O.N is +4
2X + 4(-2) = -2                                                                                                                   X + 2(-2) = 0
X= +3                                                                                                                       X= +4[/b]
So there is an increase in oxidation number of of carbon from +3 to  + 4 so  it means oxalate is oxidize.


MnO ₄ ^-(aq)              →                       Mn²⁺(aq)

In permanganate oxidation number of Mn is + 7 and in Mn⁺² oxidation number of Mn is +2 so there is a decrease  in oxidation number of manganese so it means manganese is reduced .

Quote(ii) For the titration at the equivalence point, calculate the number of moles of each of the
following that reacted. (2 points)
a) MnO4- (aq)
b) C2O4 2-(aq)

At the equivalence point in a titration, both the reactants are completely used up and only products are present in the reaction mixture.
So in a titration, equivalence  point is the amount of one reactant needed to react completely with the amount of another reactant.
Like in acid base titration- it is the amount of acid needed to neutralize the base completely or the amount of base needed to neutralize the acid completely
Exactly in the same way in a redox titration it is the amount of oxidizing agent needed  to oxidize the reducing agent completely or vice versa.
In our question permanganate ions and oxalate ions are the reacting species. Now the amount of the permanganate ions can be calculated from the information given in the question about  its molarity and its volume used to reach the equivalence point.
Volume of 0.0150 M KMnO4(aq) required to reach the equivalence point was 17.80 ml.
Molarity = moles/volume (L)
                 0.0150 M * 17.80/1000  L =0.000267 moles.
moles of permanganate  ion = molarity X volume in liters.
Using  this equation we can calculate the number of moles of permanganate needed  to oxidize oxalate ions in the 20.00 mL solutions.                                                       

Quote(iii) Calculate the total number of moles of C2O4 2- (aq) that were present in the 100.0 ml of prepared solution.

The total volume of the solution containing oxalate ion is 100ml and out of 100ml, only 20ml of the solution is titrated with permanganate solution. So the total number of permanganate ion  needed to react completely with all the oxalate ions present in 100 ml of the solution is equal to
0.0 00267 *100/20 =0.00 134 moles

Moles of MnO ₄ ^-(aq) ion = 0.00 134 moles

From the balanced chemical equation we know the ratio of the most of the permanganate ion reacting with moles of  oxalate ions.
5 moles of oxalate ion reacting with  2 moles of permanganate ions.

Using this molar ratio we can convert moles of permanganate ion calculated above to react with all oxalate ions into moles of oxalate ion by using dimensional analysis.
Moles of C₂O₄ ^2- (aq)
= ( 0.00 134 moles of MnO ₄ ^-(aq) ion ) * 5 moles of C₂O₄          ^2- (aq)/ 2 moles of MnO ₄ ^-(aq) ion )=0.00334 moles C₂O₄ ^2- (aq)

Quote(iv) Calculate the mass percent of BeC2O4(s) in the impure 0.345 g sample.

Moles of oxalate ions calculated in the given sample of beryllium oxalate using the redox titration are explained in above posts.
The chemical formula of beryllium oxalate is BeC₂O₄ and it means  1 mole of beryllium oxalate  have one mole of oxalate ions.
The total number of moles of oxalate ions calculated from titration are 0.00 334.It means the number of moles of barium oxalate in the given sample is 0.00338.Now the molar mass of beryllium oxalate is 97.03 g/mol and when we multiply the number of moles with the molar mass to calculate grams  of beryllium  oxalate in the given sample. To know the percent of beryllium oxalate in the given sample we will use  this equation
% purity = (mass of beryllium oxalate*100%)/mass of the sample.
   =   (0.324*100)/0.345 = 93.9%

What is the work of the student now.

Quote from: Jag on November 07, 2021, 04:58:17 AM
What is the work of the student now.

To understand it completely.

If finished solutions  are posted, its not a guarantee that the student understand it total. Only if small information is given in Salami style and a answer is received then it is more clear, if s( he) understand it and where are still questions.
Learning by doing is the better way.
Or is it a private lesson to one of your Student.

Quote from: Jag on November 07, 2021, 06:04:05 AM
If finished solutions  are posted, its not a guarantee that the student understand it total. Only if small information is given in Salami style and a answer is received then it is more clear, if s( he) understand it and where are still questions.
Learning by doing is the better way.
Or is it a private lesson to one of your Student.

It is for all students and not for one student.
I am going to answer many more such questions completely.