1. A student wishes to set up an electrolytic cell to plate copper onto a belt buckle. Predict the length of time it will take to plate out 2.5g of copper from a copper (II) nitrate solution using 2.5A current. At which electrode should the buckle be attached?
The second one
To predict the length of time it will take to plate out 2.5g of copper using an electrolytic cell, we need to use Faraday's Law of Electrolysis.
Faraday's Law states:
The mass of a substance produced or consumed during electrolysis is directly proportional to the quantity of electricity passed through it.
The formula for Faraday's Law is:
m = (Q * M) / (n * F)
Where:
- m is the mass of the substance (in grams)
- Q is the quantity of electricity passed through the cell (in Coulombs)
- M is the molar mass of the substance (in grams per mole)
- n is the number of moles of electrons transferred in the chemical equation
- F is Faraday's constant, approximately equal to 96,485 Coulombs per mole of electrons
In this case, we are plating out copper from a copper (II) nitrate solution. The chemical equation for this process is:
Cu2+ + 2e- -> Cu
From the equation, we can see that for every 2 moles of electrons passed through the cell, 1 mole of copper is plated out.
To find the quantity of electricity (Q), we use the formula:
Q = I * t
Where:
- I is the current (in Amperes)
- t is the time (in seconds)
We are given a current of 2.5A, and we need to solve for t.
First, we convert the mass of copper (2.5g) to moles using the molar mass of copper (63.55 g/mol):
n = 2.5g / 63.55 g/mol
Next, we can rearrange the formula for Faraday's Law to find t:
t = (n * F * M) / (Q)
Now, let's substitute the known values into the formula:
t = ((2.5g / 63.55 g/mol) * 96,485 C/mol * 63.55 g/mol) / (2.5A)
Simplifying the equation, we get:
t = 246,497 s (approximately)
Therefore, it will take approximately 246,497 seconds to plate out 2.5g of copper using a current of 2.5A.
As for which electrode the buckle should be attached to, in an electrolytic cell, the positive electrode is called the anode, and the negative electrode is called the cathode. Since we want to plate out copper onto the buckle, the buckle should be attached to the negative electrode (the cathode).