This document describes an experiment using a lemon battery to power a digital clock. It explains that the battery works via a chemical reaction between the zinc and copper electrodes in the lemon juice, salt water, or cola electrolytes. Salt water and cola worked to power the clock because they contain ions that allow electricity to flow. Distilled water did not work because it lacks dissolved ions and cannot conduct electricity between the electrodes to power the clock.

2. Introduction
This model of the chemical reactionsmakes several predictionsthat were examined in experiments publishedby
Jerry Goodisman in 2001. Goodisman notes that numerousrecent authors propose chemical reactionsfor the
lemon battery that involvedissolutionof the copper electrode into the electrolyte. Goodismanexcludes this
reaction as being inconsistentwith the experiments, and notes that the correct chemistry, which involvesthe
evolutionof hydrogen at the copper electrode, has been known for many years.

3. Introduction
This model of the chemical reactions makes several predictions that were examined in
experiments published by Jerry Goodisman in 2001. Goodisman notes that numerous recent
authors propose chemical reactions for the lemon battery that involve dissolution of the copper
electrode into the electrolyte. Goodisman excludes this reaction as being inconsistent with the
experiments, and notes that the correct chemistry, which involves the evolution of hydrogen at the
copper electrode, has been known for many years. When the electrolyte was modified by adding
zinc sulfate (ZnSO4), the voltage from the cell was reduced as predicted using the Nernst equation
for the model. The Nernst equation essentially says how much the voltage drops as more zinc
sulfate is added.This model of the chemical reactions makes several predictions that were
examined in experiments published by Jerry Goodisman in 2001. Goodisman notes that numerous
recent authors propose chemical reactions for the lemon battery that involve dissolution of the
copper electrode into the electrolyte. Goodisman excludes this reaction as being inconsistent with
the experiments, and notes that the correct chemistry, which involves the evolution of hydrogen at
the copper electrode, has been known for many years. When the electrolyte was modified by
adding zinc sulfate (ZnSO4), the voltage from the cell was reduced as predicted using the Nernst
equation for the model. The Nernst equation essentially says how much the voltage drops as more
zinc sulfate is added.

4. This model of the chemical reactions makes several predictions that were examined in experiments
published by Jerry Goodisman in 2001. Goodisman notes that numerous recent authors propose chemical
reactions for the lemon battery that involve dissolution of the copper electrode into the electrolyte.
Goodisman excludes this reaction as being inconsistent with the experiments, and notes that the correct
chemistry, which involves the evolution of hydrogen at the copper electrode, has been known for many
years. When the electrolyte was modified by adding zinc sulfate (ZnSO4), the voltage from the cell was
reduced as predicted using the Nernst equation for the model. The Nernst equation essentially says how
much the voltage drops as more zinc sulfate is added.
The Nernst equation prediction failed for strongly acid electrolytes (pH < 3.4), when the zinc electrode
dissolves into the electrolyte even when the battery is not providing any current to a circuit. The two
oxidation-reduction reactions listed above only occur when electrical charge can be transported through
the external circuit. The additional, open-circuit reaction can be observed by the formation of bubbles at
the zinc electrode under open-circuit. This effect ultimately limited the voltage of the cells to 1.0 V near
room temperature at the highest levels of acidity.The Nernst equation prediction failed for strongly acid
electrolytes (pH < 3.4), when the zinc electrode dissolves into the electrolyte even when the battery is not
providing any current to a circuit. The two oxidation-reduction reactions listed above only occur when
electrical charge can be transported through the external circuit. The additional, open-circuit reaction can
be observed by the formation of bubbles at the zinc electrode under open-circuit. This effect ultimately
limited the voltage of the cells to 1.0 V near room temperature at the highest levels of acidity.

5. Energy source
• The energy comes from the chemical change in the zinc (or
other metal) when it dissolves into the acid. The energy does
not come from the lemon or potato. The zinc is oxidized inside
the lemon, exchanging some of its electrons with the acid in
order to reach a lower energy state, and the energy released
provides the power. In current practice, zinc is produced by
electron winning of ZnSO4 or pyrometallurgic reduction of zinc
with carbon, which requires an energy input. The energy
produced in the lemon battery comes from reversing this
reaction, recovering some of the energy input during the zinc
production.

6. Material Required
• Distilled Water, Coldrink, Salt Water
• Distilled Water, Coldrink, Salt Water
•
• • Connecting Wire
•
• • Copper And Zinc Strips
•
• • Digital Clock• Connecting Wire
• • Copper And Zinc Strips
• • Digital Clock

7. Procedure
• Assemble a “connection pair” by connecting the wire carefully
thread the wire’s exposed metallic end through the holes on the
plate. Gently twist wire to secure it to the plate.
• • Afterwards, connect the black wire from the LCD clock
(negative) to one of the zinc plate. Then connect red wire from
LCD clock (positive) to piece of copper plate. Now all the
components are connected
• • Insert the copper and zinc plates into salt water such that the
metallic strips do not touch each other. The clock now starts to
work.
• • Repeat this experiment with distilled water & coldrink.

8. Observation
• As soon as we connect the wires and put the key on electricity
generated by the fruit juice flows through the clock, making the
clock run in case of salt water and coldrink. The clock does not
work when the rods are immersed in distilled water as no
current flows.

9. Result/Conclusion
• The metal strips and liquid make a simple battery that creates the
electricity to operate the clock. Salty water and coldrink work as a
device called electrochemical cell. It converts the chemical energy
stored in the metal strips into strips into electrical energy.
• A cell works because of the chemical properties of the metals inside
(in this case the copper and zinc). The different properties cause tiny
particles charged with electricity (ions) to move between the two
strips of metal. This flow is an electric current. The liquid which
conduct electricity contains the particles that allow the current to
flow, but it stops the metals touching. Electric current also flows
along the wire between the zinc and copper strips & the clock. This
current makes the clock run.

10. • SALT WATER: The ions present in common salt sodium chloride
dissociate into ions of sodium and chloride. These ions are
responsible for conduction of electricity. Potential is provided by
copper and zinc rods.
• DISTILLED WATER: There is absence of ions in distilled water
therefore the distilled water doesn't conduct electricity and hence the
clock doesn’t work. Though the H+ and OH- but the pH is 7 therefore
the ion dissociation is not enough only 10-7M H+ is present in
distilled water. so this can not conduct electricity.
• COLDRINK: The coldrink too contains ions which dissociate to
conduct electricity

11. References:
• NCERT
• • Principles of physical chemistry (Puri Sharma)
• • hometrainingtools.com
• • Wikipedia, the free encyclopedia
• • google
•