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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: vectrave on March 27, 2019, 03:38:05 AM

Title: Why isn't my galvanic cell making enough voltage?
Post by: vectrave on March 27, 2019, 03:38:05 AM

Hello!
I'm in kind of a pickle here. I made a galvanic cell of Lead and aluminium for a chemistry internal assessment but unfortunately, it didn't turn out so well and neither I nor my teacher has any clue why.
The E⁰ value of the cell is 1.53v. I got a maximum reading of 0.29v

If you don't have time to read here is what I think the sources of error could be:
1. I used filter paper as a salt bridge and I don't think it was thick enough to allow ions to flow through it.
2. I used around a 1M concentration of KCl to dip the salt bridge in.
3. I suspect either of the metals was not correct but this seems improbable as I got a voltage just not the correct one.
4. The solutions of AlNO3 and PbNO3 were kept in round-bottomed flasks with a glass cork in them for a few days before I decided to do the experiment.
5. I got a negative reading for the voltage which was weird.
6. I got a higher voltage reading only when I touched the aluminium rod to the salt bridge in the solution

I used the following procedure:

• I made 0.01M, 0.1M, 0.25M and 0.5M solutions of aluminium nitrate and a 0.1M solution of lead nitrate (both well dissolved) from lab equipment.
• I poured each of them into separate 50ml beakers. I then placed an aluminium rod (that was 50% submerged) into the AlNO3 beaker and a thin piece of lead (that was well sanded before each reading) that was fully submerged in PbNO3.
• I connected each of the metals to a multimeter via alligator clips
• I then prepared a salt bridge using 5x25cm strips of filter paper which were dipped in a solution of KCL of about 1M concentration. The filter strips were folded and stapled.
• I then placed the salt bridge in both the beakers and conducted the experiments.

I'm not in school right now and I don't have time to conduct the experiment again as the assessment is due very soon.

I will be hugely grateful to anyone who can help me

Title: Re: Why isn't my galvanic cell making enough voltage?
Post by: Borek on March 27, 2019, 03:50:44 AM

Al is always covered with a thin layer of an oxide, it is a very poor choice for a galvanic cell.