A 1.362 g sample of an iron ore that contained Fe_3O_4 was dissolved in acid and all the iron was reduced to Fe^2+. the solution was then acidified with H_2SO_4 and titrated with 39.42 mL of 0.0281 M KMnO_4 , which oxidized the iron to Fe^3+.
Net ionic equation
5Fe^(2+)+MnO_4^-+8H^+→5Fe^(3+)+Mn^(2+)+4H_2O
a) what was the percentage by mass of iron in the ore?
b) what was the percentage by mass of Fe_3O_5 in the ore
You have the balanced equation.
moles MnO4^- = M x L
Using the coefficients in the balanced equation, convert moles MnO4^- to moles Fe.
Now convert moles Fe to grams Fe. g = moles x molar mass.
%Fe = (mass Fe/mass sample)*100 = ??
Convert mass Fe to mass Fe3O4. (I assume that is Fe3O4 and not Fe3O5.)
%Fe3O4 = (mass Fe3O4/mass sample)*100 = ??
To determine the percentage by mass of iron in the ore and the percentage by mass of Fe3O4 in the ore, we need to use the given information and follow a series of steps:
Step 1: Calculate the number of moles of KMnO4 used in the titration.
Given:
- Volume of KMnO4 solution used: 39.42 mL
- Concentration of KMnO4 solution: 0.0281 M
To find the number of moles of KMnO4, we can use the formula:
moles = concentration × volume
moles KMnO4 = 0.0281 M × (39.42 mL / 1000 mL)
Convert the volume from mL to L by dividing by 1000.
Step 2: Use the stoichiometry of the balanced reaction to determine the number of moles of iron (Fe2+) reacted.
From the balanced reaction:
5Fe2+ + MnO4- + 8H+ → 5Fe3+ + Mn2+ + 4H2O
The stoichiometry tells us that 5 moles of Fe2+ react with 1 mole of KMnO4.
moles Fe2+ = 5 × moles KMnO4
Step 3: Calculate the number of moles of Fe in the sample.
Since the sample was completely dissolved in acid and all the iron was reduced to Fe2+, the moles of Fe2+ derived from the reaction in Step 2 is the same as the moles of Fe in the sample.
moles Fe = moles Fe2+
Step 4: Determine the mass of Fe in the sample using the molar mass of Fe.
The molar mass of Fe is 55.845 g/mol.
mass Fe = moles Fe × molar mass Fe
Step 5: Calculate the percentage by mass of iron in the ore.
percentage by mass of Fe = (mass Fe / mass of sample) × 100
Step 6: Determine the number of moles of Fe3+ produced.
From the balanced reaction:
5Fe2+ + MnO4- + 8H+ → 5Fe3+ + Mn2+ + 4H2O
The stoichiometry tells us that 5 moles of Fe2+ produce 5 moles of Fe3+.
moles Fe3+ = moles Fe2+
Step 7: Calculate the mass of Fe3+ in the sample using the molar mass of Fe.
The molar mass of Fe3+ is (55.845 g/mol) × 3 = 167.535 g/mol.
mass Fe3+ = moles Fe3+ × molar mass Fe3+
Step 8: Calculate the mass of Fe3O4 in the sample using the relationship between Fe and Fe3O4.
From the balanced reaction:
5Fe2+ + MnO4- + 8H+ → 5Fe3+ + Mn2+ + 4H2O
The stoichiometry tells us that 1 mole of Fe3O4 produces 5 moles of Fe3+.
moles Fe3O4 = moles Fe3+ / 5
Step 9: Calculate the mass of Fe3O4 in the sample using the molar mass of Fe3O4.
The molar mass of Fe3O4 is (55.845 g/mol) × 3 + 16.00 g/mol = 231.535 g/mol.
mass Fe3O4 = moles Fe3O4 × molar mass Fe3O4
Step 10: Calculate the percentage by mass of Fe3O4 in the ore.
percentage by mass of Fe3O4 = (mass Fe3O4 / mass of sample) × 100
By following these steps, one can calculate both the percentage by mass of iron in the ore and the percentage by mass of Fe3O4 in the ore.
To determine the percentage by mass of iron in the ore, we need to first calculate the number of moles of iron reacted with the KMnO4 solution during titration.
Step 1: Convert the mass of the iron ore to moles.
1.362 g of the iron ore contains iron.
Since we don't know the molar mass of the iron ore, we will assume it corresponds to Fe3O4.
The molar mass of Fe3O4 = (3 x atomic mass of Fe) + (4 x atomic mass of O)
The atomic mass of Fe is 55.845 g/mol, and the atomic mass of O is 16.00 g/mol.
Molar mass of Fe3O4 = (3 x 55.845) + (4 x 16.00) = 231.532 g/mol
Number of moles of Fe3O4 = mass of Fe3O4 / molar mass of Fe3O4
Number of moles of Fe3O4 = 1.362 g / 231.532 g/mol
Step 2: Calculate the moles of Fe reacted with KMnO4.
From the balanced equation, we know that 5 moles of Fe react with 1 mole of KMnO4.
Number of moles of Fe = 5 × (moles of Fe3O4) = 5 × (1.362 g / 231.532 g/mol)
Step 3: Calculate the mass of Fe.
Mass of Fe = Number of moles of Fe × molar mass of Fe
Mass of Fe = (5 × (1.362 g / 231.532 g/mol)) × 55.845 g/mol
Now that we have the mass of Fe, we can determine the percentage by mass of iron in the ore.
Percentage by mass of iron in the ore = (Mass of Fe / Mass of the iron ore) × 100
To calculate the percentage by mass of Fe3O5 in the ore, we need to calculate the mass of Fe3O5 and use the same formula as above.
The balanced equation for the reaction between Fe3O5 and KMnO4 is:
5Fe2+ + MnO4- + 8H+ → 5Fe3+ + Mn2+ + 4H2O
Note: Fe3O5 is not a commonly occurring compound, so we will assume that it is formed by the reaction.
Step 1: Calculate the moles of KMnO4 used in the titration.
Moles of KMnO4 = concentration of KMnO4 × volume of KMnO4 solution
Moles of KMnO4 = 0.0281 M × 0.03942 L
Step 2: Calculate the moles of Fe3O5 reacted with KMnO4.
From the balanced equation, we know that 1 mole of KMnO4 reacts with 5 moles of Fe3O5.
Number of moles of Fe3O5 = (moles of KMnO4) / 5
Step 3: Calculate the mass of Fe3O5.
Mass of Fe3O5 = Number of moles of Fe3O5 × molar mass of Fe3O5
Now that we have the mass of Fe3O5, we can determine the percentage by mass of Fe3O5 in the ore using the same formula as above:
Percentage by mass of Fe3O5 in the ore = (Mass of Fe3O5 / Mass of the iron ore) × 100