The amount of copper in a wire was determined by a redox titration using KMnO4 as the titrant. A 0.4185-g sample was dissolved in acid and the liberated Cu2+ quantitatively reduced to Cu+, using a reductor column. Titrating with 0.0250 M KMnO4 requires 41.27 mL to reach the endpoint. Determine the % w/w CuO in the sample of meteorite.
Cu wire to Cu^2+ to Cu^+. Then, assuming acid conditions,
5Cu^+ + MnO4^- + 8H^+ --> Mn^+ + 5Cu^2+ + 4H2O
mols MnO4^- used = M x L = ?
mols Cu+ titrated = moles CuO = 5*moles MnO4^-
grams CuO = mols CuO x molar mass CuO
%CuO = (grams CuO/mass sample)*100 = ?
Post your work if you get stuck.
To determine the % w/w CuO in the sample of meteorite, we can follow these steps:
Step 1: Calculate the moles of KMnO4 used.
Given:
- Volume of KMnO4 used = 41.27 mL
- Concentration of KMnO4 = 0.0250 M
First, convert the volume of KMnO4 used to liters:
41.27 mL = 41.27 mL * (1 L / 1000 mL) = 0.04127 L
Next, calculate the moles of KMnO4 used:
Moles of KMnO4 = Volume (in L) * Concentration (in M)
Moles of KMnO4 = 0.04127 L * 0.0250 M = 0.00103175 moles (approximately)
Step 2: Determine the ratio between Cu2+ and KMnO4.
The balanced equation for the reaction between Cu2+ and KMnO4 is:
10 Cu+ + 2 MnO4- + 16 H+ → 10 Cu2+ + 2 Mn2+ + 8 H2O
The stoichiometric ratio between Cu2+ and KMnO4 can be calculated as follows:
10 mol KMnO4 : 10 mol Cu2+
or
1 mol KMnO4 : 1 mol Cu2+
Step 3: Calculate the moles of Cu2+ present.
Since the stoichiometric ratio between Cu2+ and KMnO4 is 1:1, the moles of Cu2+ will be equal to the moles of KMnO4 used. Thus, the moles of Cu2+ present in the sample are 0.00103175 moles.
Step 4: Convert the moles of Cu2+ to grams of Cu2+.
Given:
- The molar mass of Cu2+ = 63.546 g/mol
Grams of Cu2+ = Moles of Cu2+ * Molar mass of Cu2+
Grams of Cu2+ = 0.00103175 moles * 63.546 g/mol = 0.065605 g (approximately)
Step 5: Calculate the grams of Cu in the sample.
Since Cu2+ is quantitatively reduced to Cu+, and the atomic weight of copper remains the same, we can assume that the mass of Cu2+ is equal to the mass of Cu. Therefore, the mass of Cu in the sample is also 0.065605 g.
Step 6: Calculate the moles of Cu in the sample.
Given:
- Molar mass of Cu = 63.546 g/mol
Moles of Cu = Grams of Cu / Molar mass of Cu
Moles of Cu = 0.065605 g / 63.546 g/mol = 0.001032 mol (approximately)
Step 7: Determine the grams of CuO in the sample.
The balanced equation for the reaction of CuO with Cu can be written as follows:
2 Cu2+ + Cu → 2 Cu+ + CuO
From the equation, we can see that for every mole of Cu, one mole of CuO is formed. Therefore, the moles of CuO in the sample will be the same as the moles of Cu, i.e., 0.001032 mol.
Step 8: Calculate the grams of CuO in the sample.
Given:
- Molar mass of CuO = 79.546 g/mol
Grams of CuO = Moles of CuO * Molar mass of CuO
Grams of CuO = 0.001032 mol * 79.546 g/mol = 0.081967 g (approximately)
Step 9: Calculate the % w/w CuO in the sample.
Given:
- Mass of the sample = 0.4185 g
% w/w CuO = (Mass of CuO / Mass of the sample) * 100
% w/w CuO = (0.081967 g / 0.4185 g) * 100 = 19.61%
Therefore, the % w/w CuO in the sample of meteorite is approximately 19.61%.
To determine the percentage by mass of CuO in the sample of meteorite, we need to understand the redox titration process and use stoichiometry to calculate the amount of CuO present.
1. Redox Titration:
- In this case, KMnO4 is used as the titrant, which is an oxidizing agent. It oxidizes Cu+ to Cu2+.
- The molar ratio between KMnO4 and CuO can be determined by the balanced chemical equation of the reaction:
16 KMnO4 + 10 CuO + 8 H2SO4 → 16 MnSO4 + 5 CuSO4 + 8 H2O + 2 K2SO4
2. Calculation Steps:
a. Find the moles of KMnO4 used in the titration:
Moles of KMnO4 = Molarity of KMnO4 * Volume of KMnO4 used (in L)
Convert the volume to liters: 41.27 mL = 41.27/1000 L
Moles of KMnO4 = 0.0250 mol/L * 41.27/1000 L
b. Use the balanced equation to find the moles of CuO:
From the equation, the stoichiometric ratio between KMnO4 and CuO is 10:1.
Moles of CuO = Moles of KMnO4 * (1/10)
c. Calculate the mass of CuO:
Mass of CuO = Moles of CuO * Molar mass of CuO
The molar mass of CuO (copper(II) oxide) is 79.55 g/mol.
d. Calculate the percentage of CuO in the sample:
Percentage by mass = (Mass of CuO / Mass of sample) * 100
The mass of the sample is given as 0.4185 g.
By following these steps, we can calculate the percentage by mass of CuO in the sample of meteorite.
Note: It is important to ensure the accuracy of the balanced chemical equation and the molar masses used for calculations.