Chem Talk Lab 6

In this lab we worked with conductive and non conductive solutions. We used a conductivity tester to help us determine if a solution conducted electricity. A substance that dissolves in water to make solutions that conduct electricity are called electrolytes. The solutions we tested were made of substances that were dissolved in distilled water. Only the substances that broke into charged particles when dissolved were electrolytes.

In order for a substance to conduct electricity there must be charged particles present and  they must be able to move around. Some compounds dissolve in water to form charged particles called ions. These compounds are normally made of a positively charged metal ion and a negatively charged ion to balance the charge. For example, table salt (NaCl); consists of sodium ions (Na^+) with charges of +1 and chloride ions (Cl^-) with charges of -1. When NaCl crystals dissolve in water the sodium and chloride ions separate from the crystal and become surrounded by water. Surrounded by water, the charged ions are able to move around therefore NaCl is able to conduct electricity. 

Molecular compounds do no break up into ions when they dissolve. This is because molecules do not from charged particles in a solution therefore they do not conduct electricity. Molecules that do not form ions in a solution are non-electrolytes. 

A battery is made up of two half cells. The half cell where oxidation takes place is called the anode (the negative battery electrode). The other half cell where reduction takes place is called the cathode (the positive battery electrode). 

While the battery is operating the zinc metal electrode is undergoing a reaction. The zinc ions are entering the zinc nitrate solution while the electrons are traveling through the wire. The electrons reach the copper metal electrode where reduction occurs. When electrons reach the copper cathode they enter into reduction. Copper ions from the solution combine with electrons to make neutral copper metal atoms. The copper metal electrode then increases in mass because copper metal is attaching to it. The solution was originally prepared by dissolving Cu(NO3)2 crystals in water. When the compound dissolves they are both surrounded by water molecules. As the positively charged copper ions are used up the negatively charged nitrate ions are being pushed out. They are forced to go through the salt bridge. They enter the zinc half cell where zinc ions are being created at the anode. Then there is a need for more negative ions to balance the increasing positive charge on zinc ions. 

Electricity only runs spontaneously in one direction in a battery due to the relative activities of the two metal electrodes used in the half reactions. In our lab the Zn metal atoms were converting to Zn2+ ions and from Cu2+ ions to Cu metal atoms. In the metal activity series zinc metal is more reactive than copper metal therefor zinc will react spontaneously with Cu2+ and Cu will not react spontaneously with Zn2+. 

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