A 0.750 g sample of an unknown solid is dissolved in 100 mL of water and acidfied with 25 mL of 3 M H2SO4 then titrated with a 0.0200 M KMnO4 solution. If the unknown solid requires 12.5 mL of the KMnO4 solution to reach the endpoint, what is the % sodium oxalate in the unknown solid? Assume the only compound in the unknown solid that reacts with the KMnO4 solution is sodium oxalate. Report you answer as a percentage, but do not include the percent sign, %, in your answer
You can finish balancing the equation but the following is all you need.
2MnO4^- + 5C2O4^2- ==> 10CO2 + 2Mn^2+
mols MnO4^- = M x L = ?
Using the coefficients in the balanced equation, convert mols MnO4^- to mols C2O4^2-.
Then convert mols C2O4^2- to mols Na2C2O4 (that's the same value). Convert mols Na2C2O4 to g. g Na2C2O4 = mols Na2C2O4 x molar mass Na2C2O4.
%Na2C2O4 = (grams Na2C2O4/0.750)*100 = ?
14.5
To solve this problem, we need to calculate the amount of sodium oxalate in the unknown solid and then determine its percentage.
Let's break down the steps:
Step 1: Calculate the number of moles of KMnO4 used.
To find the number of moles of KMnO4 used, we can use the equation:
Moles of KMnO4 = Volume of KMnO4 solution (in L) × Concentration of KMnO4 solution (in mol/L)
Given that the volume of KMnO4 used is 12.5 mL (or 0.0125 L) and the concentration of KMnO4 solution is 0.0200 M, we can calculate the moles:
Moles of KMnO4 = 0.0125 L × 0.0200 mol/L
Step 2: Determine the stoichiometry between KMnO4 and sodium oxalate.
The balanced chemical equation between KMnO4 and sodium oxalate is:
5 C2O4^-2 + 2 MnO4^-1 + 16 H+ → 2 Mn^2+ + 10 CO2 + 8 H2O
From the equation, we can see that 5 moles of sodium oxalate (C2O4^-2) react with 2 moles of KMnO4. Therefore, the moles of sodium oxalate can be calculated as:
Moles of sodium oxalate = (Moles of KMnO4) × (5/2)
Step 3: Calculate the mass of sodium oxalate.
The molar mass of sodium oxalate (Na2C2O4) can be found by adding up the atomic masses of each element: sodium (Na), carbon (C), and oxygen (O). The atomic masses are:
Na: 22.99 g/mol
C: 12.01 g/mol
O: 16.00 g/mol
Molar mass of Na2C2O4 = (2 × Na) + (2 × C) + (4 × O)
Having obtained the molar mass, we can now calculate the mass of sodium oxalate:
Mass of sodium oxalate = (Moles of sodium oxalate) × (Molar mass of Na2C2O4)
Step 4: Calculate the percentage of sodium oxalate.
Finally, we can determine the percentage of sodium oxalate by using the formula:
% Sodium oxalate = (Mass of sodium oxalate / Mass of unknown solid) × 100
Given that the unknown solid weighs 0.750 g, we can substitute the values and solve the equation to find the percentage of sodium oxalate.
% Sodium oxalate = (Mass of sodium oxalate / 0.750 g) × 100
By following these steps and substituting the given values, you will be able to calculate the percentage of sodium oxalate in the unknown solid.