answer
2) 0.356 g of the oxalate unknown to use
3) 0.00081139 moles of oxalate in the unknown
steps
Oxalate Titration Calculations
We can use the information given to calculate the concentration of permanganate solution used to titrate the oxalate unknown:
mol KMnO4 = mol oxalate
Molarity = mol/L
The balanced chemical equation for the reaction between permanganate and oxalate is:
5 C2O42- + 2 MnO4- + 16 H+ → 2 Mn2+ + 10 CO2 + 8 H2O
From the equation, we can see that 2 moles of permanganate react with 5 moles of oxalate. Therefore, the number of moles of oxalate in the sample can be calculated as:
mol oxalate = (mol KMnO4) x (5 mol oxalate/2 mol KMnO4)
To determine the mass of oxalate required to use 35.0 mL of permanganate solution, we need to use the following formula:
mass = (mol x molar mass)/moles
where molar mass of oxalate = 90.04 g/mol
First, we calculate the number of moles of permanganate solution used:
mol KMnO4 = Molarity x Volume (in L)
mol KMnO4 = (26.8 mL/1000 mL/L) x (Molarity)
Next, we calculate the number of moles of oxalate:
mol oxalate = (mol KMnO4) x (5 mol oxalate/2 mol KMnO4)
Now, we can calculate the mass of oxalate required to use 35.0 mL of permanganate solution:
mass = (mol oxalate x molar mass)/moles
mass = [(mol KMnO4) x (5 mol oxalate/2 mol KMnO4) x (90.04 g/mol)]/[(26.8 mL/1000 mL/L) x (Molarity)]
Substituting the given values:
mass = [(35.0 mL/1000 mL/L) x (0.0227 mol/L) x (5/2) x (90.04 g/mol)]/[(26.8 mL/1000 mL/L) x (Molarity)]
mass = 0.356 g
Therefore, the student should weigh out 0.356 g of the oxalate unknown to use 35.0 mL of permanganate solution.
The number of moles of oxalate can be calculated using the following formula:
moles = Molarity x Volume (in L)
Substituting the given values:
moles oxalate = 0.0357 L x 0.0227 mol/L
moles oxalate = 0.00081139 mol
Therefore, there are 0.00081139 moles of oxalate in the unknown.
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