The Effect of pH of Electrolyte on Conductivity and Voltage
How does changing the pH level of lemon juice affect the voltage and conductivity
produced in a lemon juice cell?
Many of today's devices are powered by what is called a battery. Your computers,
calculators, mobile phones, iPods, and other electronic gadgets and devices function with the
supply of energy from batteries. We use batteries everyday, yet we don't often question what
a battery is made of or consider the factors of its performance. If you have ever taken physics,
you would understand that high voltage batteries supply more energy than low voltage
batteries, but ...view middle of the document...
This will cause an electron transfer from the negative electron-gaining electrode back
to the positive electron-donating electrode. This constant movement of electrons creates an
electrical current, hence a functioning battery.
The movement of electrons within the cell can be explained by a redox reaction. In the
negative electrode, oxidation occurs. This means that the negative electrode is losing
electrons. Reduction occurs in the positive electrode, which gains electrons from the positive
electrode (Derry, 2008).
In this investigation, lemon juice is used as the electrolyte of the battery.
Oxidation occurs as zinc dissolves in the lemon electrolyte and leaves 2 moles of electrons (e) to travel through the wire to the copper electrode.
Zn Zn2+ + 2e-
Reduction occurs as the two moles of H+ ions in the electrolyte combine with the 2 moles of
electrons from the copper electrode to form a hydrogen molecule. This release of hydrogen
can be seen as bubbles when the experiment is conducted.
2H+ + 2e H2
Zn + 2H+ Zn2++ H2 (g)
Lemon juice has a low pH, meaning that it is an acid. Lemon juice contains H+ ions, which are
The Lemon Juice
charged particles responsible for conducting electricity. "The electrical conductivity is
proportional to the concentration of ions." (Derry, 2008) This theory should then support the
idea that if the concentration of the lemon juice decrease, the moles of ions will decrease,
decreasing the flow of electrons and the corresponding voltage.
According to Ohm’s Law, current is proportional to voltage. This can be shown in the
Low conductivity causes low current, and low current causes low voltage.
If the lemon juice’s pH level is increased by dilution, the conductivity and voltage
produced will decrease. The decreasing moles of ions will also decrease the lemon juice’s
conductivity. This means that electrons will not flow as freely when there is a fewer
concentration of ions in the solution. When the electron flow decreases, the voltage will also
decrease because current and voltage are directly proportional to each other.
1. Cut the lemon in half and squeeze the juice into a beaker.
2. Place a piece of muslin cloth on the funnel that is placed in another beaker.
3. Pour the lemon juice into the beaker with the flask and the muslin cloth. Make sure to
squeeze the excess lemon juice soaked in the muslin cloth. This beaker should have no
4. Pour 40ml of the filtered lemon juice into a 50 ml graduated cylinder.
5. Once you have 40 ml of the juice measured, pour it into the 200ml beaker with the zinc
and copper electrodes. The zinc and copper electrodes are to be taped to the opposite
sides of the beaker. The distance between the electrodes is to be kept constant. This is
to ensure that the ions travel the same distance throughout the entire experiment. In