In an experiment like the one you will complete, a student collected the followi

Question

In an experiment like the one you will complete, a student collected the following data. Use this information to complete the questions below. YOU MUST SHOW ALL CALCULATIONS. Change in Mass of Anode: -0.022 g Change in Mass of Cathode: +0.021 g Average Current: 38.7 mA Time of Electrolysis: 1865 s a) Calculate the number of Coulombs passed during this experiment. b) Calculate the number of moles of electrons passed during this experiment. c) Calculate the number of moles of Cu^2+ ions deposited. d) Using the average of the change in mass of copper from the electrodes in the electrolytic cell, calculate the molar mass of copper.

Explanation / Answer

change in mass at electrode = 0.022g

current passed = 38.7 mA = 38.7 x 10-3 A = 38.7 x 10-3 C/s

time = 1865 s

a) The amount of current passed in Coulombs is:

(38.7 x 10-3 C/s)(1865 s) = 72.175 C

The number of Coulombs passed during the experiment is 72.175 C.

b) 1 mol of e- = 1 Faraday constant = 96485 C

mol of e- produced/consumed at electrode = (72.175 C)/(1mol e/ 96485 C) = 0.000748 mol

Therefore, moles of electrons passed during the experiment = 7.48 x 10-4 mol.

c)      Cu2+(aq) + 2e- -----> Cu(s)

each mole of Cu2+ needs 2 mol of e- for deposition.

Hence, moles of Cu2+ deposited = (7.48 x 10-4 mol e-)(1 mol Cu2+/2 mol e-) = 3.74 x 10-4 mol Cu2+.

d) moles of copper deposited = 0.000374

mass of Cu deposited = 0.022 g

Therefore, molar mass = mass/ moles = 0.022g/0.000374 mol = 58.8 g/mol

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