CHEMISTRY PROJECTClass 12th TOPIC: Electrochemical cells I am grateful to my . Certificate This is to be certify that student of class XII A has successfully completed the research on his major project (ELECTROCHEMICAL CELL) under guidance of (subject teacher for session (2015 -2016) who has been there for all the practicals ) Signature of teacher Signature of examiner throughouty project. The zinc and copper are called the electrodes.5-volt "battery". The lemon battery is described in some textbooks in order to illustrate the type of chemical reaction (oxidation-reduction) that occurs in batteries. a battery properly consists of multiple cells. connected in either parallel or series pattern. There are many variations of the lemon cell that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes. who used brine (salt water) instead of lemon juice. Batteries are used to illustrate the connection between chemistry and electricity as . Abstract An electrochemical cell is a device capable of either deriving electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy. (Actually a single "Galvanic cell". A common example of an electrochemical cell is a standard 1.) The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta. and the juice inside the lemon is called the electrolyte. The Nernst . Goodisman excludes this reaction as being inconsistent with the experiments. which involves the evolution of hydrogen at the copper electrode. When the electrolyte was modified by adding zinc sulfate (ZnSO4). Goodisman notes that numerous recent authors propose chemical reactions for the lemon battery that involve dissolution of the copper electrode into the electrolyte. has been known for many years. Batteries serve to illustrate the principles of oxidation-reduction reactions.well as to deepen the circuit concept for electricity. and notes that the correct chemistry. THEORY This model of the chemical reactions makes several predictions that were examined in experiments published by Jerry Goodisman in 2001. The fact that different chemical elements such as copper and zinc are used can be placed in the larger context that the elements do not disappear or break down when they undergo chemical reactions. the voltage from the cell was reduced as predicted using the Nernst equation for the model. sulfuric.When the battery is hooked up to an external circuit and a significant electrical current is flowing.) doesn't affect the voltage except through the pH value. etc. the voltage from the cell depended upon the acidity of the electrolyte.4). Finally.equation essentially says how much the voltage drops as more zinc sulfate is added. The two oxidation-reduction reactions listed above only occur when electrical charge can be transported through the external circuit. This effect is also predicted by the Nernst equation. The Nernst equation prediction failed for strongly acid electrolytes (pH < 3. hydrogen gas evolves as bubbles from the copper electrode. The addition of copper sulfate (CuSO4) did not affect the voltage. as predicted by the zinc oxidation reaction above. as measured by its pH. the zinc electrode loses mass. The additional. Similarly. open- . when the zinc electrode dissolves into the electrolyte even when the battery is not providing any current to a circuit. the particular acid that was used (citric. decreasing acidity (and increasing pH) causes the voltage to fall. hydrochloric. This result is consistent . circuit reaction can be observed by the formation of bubbles at the zinc electrode under open-circuit. The zinc is oxidized inside the lemon. This effect ultimately limited the voltage of the cells to 1. zinc is produced by electron winning of ZnSO4 or pyrometallurgic reduction of zinc with carbon. . exchanging some of its electrons with the acid in order to reach a lower energy state. Energy source The energy comes from the chemical change in the zinc (or other metal) when it dissolves into the acid.0 V near room temperature at the highest levels of acidity. The energy produced in the lemon battery comes from reversing this reaction. which requires an energy input. and the energy released provides the power. The energy does not come from the lemon or potato. In current practice. recovering some of the energy input during the zinc production. 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. Repeat this experiment with distilled water & coldrink. Then connect red wire from LCD clock (positive) to piece of copper plate. EXPERIMENTAL WORK MATERIAL REQUIRED DISTILLED WATER. connect the black wire from the LCD clock (negative) to one of the zinc plate. COLDRINK. Afterwards. Gently twist wire to secure it to the plate. OBSERVATION As soon as we connect the wires and put the key on electricity generated by the fruit juice . SALT WATER CONNECTING WIRE COPPER AND ZINC STRIPS DIGITAL CLOCK PROCEDURE Assemble a “connection pair” by connecting the wire carefully thread the wire’s exposed metallic end through the holes on the plate. The clock now starts to work. The liquid which conduct electricity contains the particles that allow the current to flow. Salty water and coldrink work as a device called electrochemical cell.flows through the clock. SALT WATER: The ions present in common salt sodium chloride dissociate into ions of sodium and chloride. A cell works because of the chemical properties of the metals inside (in this case the copper and zinc). Potential is provided by copper and zinc rods. making the clock run in case of salt water and coldrink. DISTILLED WATER: There is absence of ions in distilled water therefore the distilled water doesn't . but it stops the metals touching. This current makes the clock run. Result/conclusion The metal strips and liquid make a simple battery that creates the electricity to operate the clock. The different properties cause tiny particles charged with electricity (ions) to move between the two strips of metal. It converts the chemical energy stored in the metal strips into strips into electrical energy. This flow is an electric current. These ions are responsible for conduction of electricity. Electric current also flows along the wire between the zinc and copper strips & the clock. The clock does not work when the rods are immersed in distilled water as no current flows. so this can not conduct electricity. COLDRINK: The coldrink too contains ions which dissociate to conduct electricity.but the pH is 7 therefore the ion dissociation is not enough only 10-7M H+ is present in distilled water. Though the H+ and OH. Ions in coldrink are Bibliography NCERT Principles of physical chemistry (Puri Sharma) hometrainingtools.com Wikipedia.conduct electricity and hence the clock doesn’t work. the free encyclopedia google . TITLE PAGE ELECTROCHEMIST RY: . (Production of current through SELFMADE battery) .
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