ou weigh out Potassium Permanganate,
Mass of KMnO4 (MW=158.034).......... 0.1569 g
You dissolve it completely in water.......... 46.00 mL
(a) Molarity of MnO4- solution........................... ________________ M
You pipet out your UNKNOWN............. 0.90 mL
You acidify and titrate it with your KMnO4 solution until the permanganate color persists.
Volume of permanganate solution.......... 14.61 mL
(b) Molarity of the HOOH in the UNKNOWN...................................._____________ M
mols KMnO4 = grams/molar mass
M = mols/L soln
Write and balance the equation for KMnO4 + HOOH.
In the titration, mols KMnO4 = M x L = ?
Convert mols KMnO4 to mols HOOH using the coefficients in the balanced equation.
Then M HOOH = mols HOOH/L HOOH.
To find the molarity of the MnO4- solution (part a), we can use the formula:
Molarity (M) = (moles of solute) / (volume of solution in liters)
1. Calculate the moles of KMnO4:
Moles = Mass / Molar mass
Moles = 0.1569 g / 158.034 g/mol = 0.000992 mol
2. Convert the volume of the KMnO4 solution from milliliters to liters:
Volume = 46.00 mL / 1000 mL/L = 0.04600 L
3. Now, divide the moles of KMnO4 by the volume to obtain the molarity:
Molarity = 0.000992 mol / 0.04600 L ≈ 0.02157 M
Therefore, the molarity of the MnO4- solution is approximately 0.02157 M.
Moving on to part b, figuring out the molarity of HOOH in the unknown solution:
We'll use the balanced chemical equation to help us determine the ratio between KMnO4 and HOOH:
2 KMnO4 + 3 H2O2 + 2 H2SO4 -> 2 MnSO4 + 4 H2O + 3 O2 + K2SO4
From the equation, we can see that the ratio between KMnO4 and HOOH is 2:3.
1. Calculate the moles of KMnO4 used in the titration:
Moles of KMnO4 = Molarity of KMnO4 * Volume of KMnO4 solution in liters
Moles of KMnO4 = 0.02157 M * 0.01461 L = 0.0003159 mol
2. Since the ratio between KMnO4 and HOOH is 2:3, we can calculate the moles of HOOH:
Moles of HOOH = (2/3) * Moles of KMnO4
Moles of HOOH = (2/3) * 0.0003159 mol ≈ 0.0002106 mol
3. Finally, calculate the molarity of HOOH in the unknown solution:
Molarity of HOOH = Moles of HOOH / Volume of HOOH in liters
Molarity of HOOH = 0.0002106 mol / 0.00090 L ≈ 0.234 M
Therefore, the molarity of the HOOH in the unknown solution is approximately 0.234 M.