Investigating in the effect of ion concentration in electrolytes on the potential difference in a voltaic cell
Introduction
When two electrodes made of different metals are connected together in a voltaic cell, the chemical energy present is converted into electrical energy and an electromotive force is generated. This force, called the electrode potential, is normally measured under standard conditions, which is 298K, 1 mol dm-3 solution for the electrolyte. However when one measures the electrode potential in a voltaic cell, the conditions are often not at standard.
The concentration of ions in the electrolyte solution affects the number of collisions the ions would have with the electrode. If the concentration increases, then probability of an ion coming into contact with the electrode increases.
This experiment will mainly focus on the effect of changing ion concentration in electrolytes on the potential difference generated. Three different combinations of metals and electrolytes will be used to assess the general effect.
Purpose
The purpose of this investigation is to determine whether the concentration of ions in the electrolyte in a voltaic cell will affect the potential difference.
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Hypothesis
If the concentration of ions in the electrolyte increases, then so will the potential difference in the voltaic cell.
When two electrodes are connected in a voltaic cell, the electrode potential depends not only on the nature of the electrodes themselves, but also on the number of ions available in the electrolyte. If there are more ions available, then the appropriate oxidation or reduction reaction would have more chance of occurring.
Apparatus
* Iron electrode, 3cm x 2cm
* Copper electrode, 3cm x 2cm
* Iron (II) Sulfate solution – 0.2 mol dm-3, 400ml
* Copper (II) Sulfate solution – 0.2 mol dm-3, 400ml
* Zinc Sulfate solution – 0.2 mol dm-3, 400 ml
* Electronic voltmeter
* Connecting wires with alligator clips x 2
* Beakers, 50ml±1x 2
* Distilled water, 1 litre
* Salt bridge (coffee filter paper saturated with potassium nitrate).
* Measuring cylinder – 25ml±0.3, x 2
Variables
Independent
* Electrolyte content
* Electrolyte concentration
Dependent
* Voltage
Controlled
* Type of electrode
* Volume of electrolyte
Method
1. Connect the copper and iron electrode to the voltmeter by using the connecting wire. Attach the electrodes to the wires by alligator clips.
2. By using a measuring cylinder, measure out 50 ml of iron (II) sulfate and pour it into a beaker. Do so for copper (II) sulfate as well. Ensure that both electrolytes are of the same concentration.
