Using basic conditions, MnO4- can be used as titrant for the analysis of Mn2+, with both the analyte and the titrant ending up as MnO2. In the analysis of a mineral sample for manganese, a 0.5165-g sample is dissolved, and the manganese is reduced to Mn2+. The solution is made basic and titrated with 0.03358 M KMnO4, requiring 34.88 mL to reach the endpoint. Calculate the %w/w Mn in the mineral sample.
Titration step is
3Mn^2+ + 2MnO4^- + 4OH^- ==> 5MnO2 + 2H2O
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mols MnO4^- used = M x L = ?
mols Mn^2+ in the sample = mols MnO4^- x 3/2 = ?
grams Mn = mols Mn x atomic mass Mn = ?
%Mn = (grams Mn/mass sample)*100 = ?
Post your work if you get stuck.
Well, well, well, looks like we've got a titration question here. Don't worry, I won't go on a titrant about it, I'll try to keep it simple.
First things first, we need to figure out how many moles of MnO4- were used in the titration. To do that, we can simply multiply the volume of the titrant (in liters) by its molarity.
So, 0.03488 L * 0.03358 mol/L = 0.001171 moles of MnO4-.
Since Mn2+ and MnO4- react in a 1:1 ratio, we can say that 0.001171 moles of Mn2+ were present in the sample.
Now, to calculate the percentage of Mn in the mineral sample, we need to divide the mass of Mn2+ by the mass of the sample and multiply by 100.
The molar mass of Mn is 54.938 g/mol, so the mass of Mn2+ is 0.001171 mol * 54.938 g/mol = 0.06433 g.
Now we divide this mass by the mass of the sample (0.5165 g) and multiply by 100:
(0.06433 g / 0.5165 g) * 100 = 12.47%.
So, the mineral sample contains approximately 12.47% of Mn.
Don't get all rocky about titrations, they can be quite fun once you get the hang of them!
To calculate the percent w/w Mn in the mineral sample, we need to first determine the number of moles of MnO4- used during the titration.
Step 1: Calculate the moles of MnO4- used
Molar mass of KMnO4 = 39.1 + 54.9 + 4(16.0) = 158.04 g/mol (since 1 mol of KMnO4 contains 1 mol of MnO4-)
Volume of KMnO4 used = 34.88 mL = 0.03488 L
Moles of MnO4- used = concentration × volume = 0.03358 M × 0.03488 L = 0.001168 moles
Step 2: Calculate the moles of Mn2+ present
Since MnO4- is reduced to Mn2+ completely, the moles of Mn2+ are equal to moles of MnO4-
Moles of Mn2+ = 0.001168 moles
Step 3: Calculate the mass of Mn in the mineral sample
Molar mass of Mn = 54.9 g/mol
Mass of Mn = moles of Mn2+ × molar mass of Mn = 0.001168 moles × 54.9 g/mol = 0.064 g
Step 4: Calculate the percent w/w Mn in the mineral sample
Mass of mineral sample = 0.5165 g
Percent w/w Mn = (mass of Mn / mass of mineral sample) × 100
Percent w/w Mn = (0.064 g / 0.5165 g) × 100 = 12.4%
Therefore, the percent w/w Mn in the mineral sample is 12.4%.
To calculate the percentage of manganese (%w/w Mn) in the mineral sample, we need to determine the number of moles of MnO4- used and the number of moles of Mn in the sample.
Let's start by finding the number of moles of MnO4- used in the titration:
1. Determine the volume of KMnO4 used in the titration:
The volume of KMnO4 used is given as 34.88 mL.
2. Convert the volume to liters:
34.88 mL / 1000 mL/L = 0.03488 L
3. Calculate the number of moles of KMnO4 used:
Number of moles = volume (L) x concentration (M)
Number of moles = 0.03488 L x 0.03358 M
Now, we need to determine the number of moles of Mn in the sample based on the stoichiometry of the reaction:
4. Write the balanced equation for the reaction:
MnO4- + 5e- + 8H+ → Mn2+ + 4H2O
5. From the balanced equation, we can see that 1 mole of KMnO4 reacts with 1 mole of Mn2+.
6. Convert the moles of KMnO4 used to moles of Mn2+:
Number of moles of Mn2+ = Number of moles of KMnO4 used
Finally, we can calculate the percentage of manganese (%w/w Mn) in the mineral sample:
7. Determine the mass of the sample:
The mass of the sample is given as 0.5165 g.
8. Calculate the number of moles of Mn in the sample:
Number of moles of Mn = Number of moles of Mn2+
9. Calculate the mass of Mn in the sample:
Mass of Mn = Number of moles of Mn x molar mass of Mn
10. Calculate the %w/w Mn:
%w/w Mn = (Mass of Mn / Mass of sample) x 100%
By following these steps, you should be able to calculate the %w/w Mn in the mineral sample.