# Need help with electrochemistry lab

• qpham26
In summary, Borek attempted to solve a homework problem involving calculating the concentration of a metal ion using the Nernst equation. He found that the answer was very small, and that the calculation may have been incorrect.
qpham26

## Homework Statement

Simplified lab procedure:

I have 3 wells (from well-plate)
one with Cu(NO3)2 and a piece of Cu(s)
one with AgNO3 and a small piece of Ag(s)
last one with Zn(NO3)2 and a piece of Zn(s)
Salt bridges are soaked with KNO3

All of the solutions above have molarity of 0.10M

A few drops of 6M NH3 (aq) was added to the well with Cu(s)

And I used the volt meter to measure the voltage between Cu and the other two
Cu and Ag : 0.521 V
Cu and Zn : 0.619 V

And they want me to calculate the concentration of Cu2+
using Nernst equation

## Homework Equations

Cu2+ + 2e- ⇔ Cu(s) Eo = 0.34V

Ag+ + e- ⇔ Ag(s) Eo = 0.80V

Zn2+ + 2e- ⇔ Zn(s) Eo = -0.76V

Ecell = Eocell - $\frac{0.0592}{n}$logQ

## The Attempt at a Solution

First question I have, so the value that we measure, is that the total Ecell ?
and let do the first case, since both are used for calculation [Cu2+]
For Zn and Cu

Zn(s) + Cu2+(aq) ⇔ Zn2+(aq) + Cu(s)
Eo = 0.76 + 0.34 = 1.1 V

And now with [Zn2+] = 0.10M and the measured Ecell I just need to plug this into the Nernst equation to get Q.

The same method would be applicable to Ag. Assuming I got the above correctly.
However, the answer I got for [Cu2+] is very small, 5 x 10^(-18)

and When I do the same thing for Ag
i got a different value 8.5 x 10^-5
So i think there is something wrong.

Last edited:
Hard to say if you are not doing any mistake without seeing exact calculations, but the logic behind things you wrote so far looks OK to me.

For Zn and Cu

0.619 = 1.10 - $\frac{0.059}{2}$log$\frac{[Zn2+}{[Cu2+]}$

I plugged it into wolfram alpha, so the answer can't have any mathematical errors.

as for Cu and Ag
Cu(s) + 2Ag+ → Cu2+(aq) + 2Ag(s)
the equation is

0.521 = 0.46 - $\frac{0.059}{2}$log$\frac{[Cu2+}{[Ag+]^2}$

qpham26 said:
0.619 = 1.10 - $\frac{0.059}{2}$log$\frac{[Zn2+}{[Cu2+]}$

Looks OK, unless I am wrong as well.

That is, it doesn't look OK - why don't you format it as a whole using LaTeX?

$$0.619 = 1.10 - \frac{0.059}{2}\log(\frac{[Zn^{2+}]}{[Cu^{2+}]})$$

Hi Borek, what doesn't look Ok beside the Latex format?
was the chemical eq. correct?
and is the Nernst eq. set up right?

I was referring to formatting only.

Borek, If the set up was right, how come i am getting 2 different answer?
does it have to do with the measurement then?

## 1. What is electrochemistry?

Electrochemistry is the study of the relationship between electricity and chemical reactions. It involves the movement of electrons to produce or drive a chemical reaction.

## 2. What is the purpose of an electrochemistry lab?

The purpose of an electrochemistry lab is to study and analyze the behavior of chemical reactions that involve electricity. This can include measuring the rate of a reaction, determining the products of a reaction, and studying the effects of different variables on the reaction.

## 3. What equipment is typically used in an electrochemistry lab?

Some common equipment used in an electrochemistry lab includes a potentiostat, electrodes, a reference electrode, a working electrode, a counter electrode, and a power supply. Other equipment such as beakers, burettes, and stirrers may also be used depending on the specific experiment being conducted.

## 4. What are some potential safety precautions to take in an electrochemistry lab?

Some safety precautions to take in an electrochemistry lab include wearing appropriate personal protective equipment, such as goggles and gloves, handling chemicals and equipment with care, and following proper disposal procedures for waste materials. It is also important to have a clear understanding of the experiment and its potential hazards before beginning.

## 5. What are some common applications of electrochemistry?

Electrochemistry has a wide range of applications, including battery technology, corrosion prevention, and wastewater treatment. It is also used in various industries such as pharmaceuticals, electronics, and food production. Additionally, electrochemistry plays a crucial role in research and development in fields such as energy storage and environmental sustainability.

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