An investigation to discover how the mass of deposited metal is related to the current that flows through an electrolyte.

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Sarah Lee

An investigation to discover how the mass of deposited metal is related to the current that flows through an electrolyte

An electroplating company needs to know how the mass of deposited metal is related to the current that flows through an electrolyte. I have been asked to investigate…

Possible input variables

The size of current, metal at the electrode, concentration of solution, surface area exposed to electrolyte and the time exposed the metal is exposed may effect the experiment.

Possible output variables

If I change any number of the input variables the mass of the metal deposited at the cathode and the mass lost at the anode will be affected.

My input variable

I have decided to change the current that I pass through the electrolyte.

My outcome variable

I will need to measure or observe the mass of metal deposited at the cathode.

My control variable

To make my experiment fair, I will keep the concentration of the solution, metal at the electrodes, surface area of the metal exposed to the electrolyte and the time the metal is exposed the same each time I do the experiment.

Scientific knowledge

In the electrolysis of copper solution with copper electrodes copper is deposited at the cathode. There are positively charged copper ions in the copper sulphate solution, which are then attracted to the negatively charged cathode and deposited when they combine with +2 electrons. In order for current to flow and to maintain the same number of copper ions at all times atoms of copper lose electrons, which go into the solution and flow as current. The atoms are therefore charged positive ions of copper, which are attracted to the cathode.

    The sulphate ions in the solution are negatively charged so are attracted to the anode. (However they aren’t deposited in this solution). The copper ions in the solution are positively charged and therefore attracted to the cathode, which are deposited.

If I double the current for the same amount of time the charge flowing will also double. Therefore the number of ions deposited in the time will also double therefore the mass of the deposit is also double

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Prediction

I predict that, as the current increases the mass of the deposit also increases. I predict, as the current doubles so will the deposit. This is because

Charge = time x current

If I increase the current across the solution the charge at the cathode will be greater therefore giving me more deposit.

Equipment list

I need the following to carry out a successful experiment…

Lab pack, beaker of copper sulphate solution, copper anode, copper cathode, covered wires, an ammeter, timer, scales

Recording results

I will use a table and a line graph ...

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