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Redox Chemistry

Pearson
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Electrochemistry is the study of chemical reactions which involve the flow of electrons. We often refer to these as redox reactions, standing for reduction and oxidation. Remember that when you have reduction, you also have oxidation. They occur together. We can see electrochemical reaction happening. Here I have a solution of copper sulfate and I have iron powder. Let's see what happens when I put the iron powder into the solution of copper sulfate. The iron powder is a black powder. So you can see in the reaction that the black powder is turning to a shiny solid. So in this reaction, which species is being reduced? So in this reaction, the copper ions are being reduced to metallic copper. When we look at the equation, we have added iron solid to a solution containing copper ions, and we obtain a copper solid. That's the solid that's forming in the beaker. So what we can say is the copper ions are picking up electrons and being reduced to copper solid. So the copper, in this case, is reduced. Likewise, the iron solid is oxidized to iron 2 plus. So remember, in these electrochemical reactions, when something is oxidized, something else is reduced. The couple together. We always have one with the other. We can use the table of reduction potentials in our textbook to determine if a chemical reaction will occur. So let's see what happens with the reverse reaction. Up here, I have a solution of iron sulfate, so iron 2+ ions in solution, and I have copper metal. Let's see what happens when I place this copper into the iron solution. You can see that no reaction is occurring. So the reverse reaction in this case does not happen. We can explain this using the table of reduction potentials. So looking at the table of reduction potentials, the reduction potential of copper is plus 0.33 v. The reduction potential of iron is -0.44 v. So copper, in this case, has a higher reduction potential. It preferentially wants to be reduced. Thus, the iron will be oxidized. So we can use these table of reduction potentials to determine if a reduction will occur. So let's see what happens when I add this zinc metal to the hydrochloric acid solution. You can see that the reaction is bubbling. We are producing hydrogen gas. So the zinc metal is being oxidized to zinc ions, and the hydrogen is forming hydrogen gas. If we look at the table of reduction potentials, we can see that the hydrogen preferentially wants to be reduced. So we're forming hydrogen gas, and the zinc is oxidized to zinc ions. We talk about electrochemical reactions, we often talk about oxidizing agents and reducing agents. The oxidizing agent is something that causes a species to be oxidized, and a reducing agent is something that causes a species to be reduced. So let's see the reaction when I take this copper metal and put it into a beaker containing silver nitrate solution. So you can see that when I place this copper into the solution, the color of the metal is changing. So which species is the reducing agent in this reaction? So in this reaction, the copper metal is the reducing agent. It's causing the silver ions to be reduced to silver metal, which you can see on the strip of copper here. They're depositing there on the surface. So remember that the agents are the reactants, and they're causing something to be reduced or oxidized.
Electrochemistry is the study of chemical reactions which involve the flow of electrons. We often refer to these as redox reactions, standing for reduction and oxidation. Remember that when you have reduction, you also have oxidation. They occur together. We can see electrochemical reaction happening. Here I have a solution of copper sulfate and I have iron powder. Let's see what happens when I put the iron powder into the solution of copper sulfate. The iron powder is a black powder. So you can see in the reaction that the black powder is turning to a shiny solid. So in this reaction, which species is being reduced? So in this reaction, the copper ions are being reduced to metallic copper. When we look at the equation, we have added iron solid to a solution containing copper ions, and we obtain a copper solid. That's the solid that's forming in the beaker. So what we can say is the copper ions are picking up electrons and being reduced to copper solid. So the copper, in this case, is reduced. Likewise, the iron solid is oxidized to iron 2 plus. So remember, in these electrochemical reactions, when something is oxidized, something else is reduced. The couple together. We always have one with the other. We can use the table of reduction potentials in our textbook to determine if a chemical reaction will occur. So let's see what happens with the reverse reaction. Up here, I have a solution of iron sulfate, so iron 2+ ions in solution, and I have copper metal. Let's see what happens when I place this copper into the iron solution. You can see that no reaction is occurring. So the reverse reaction in this case does not happen. We can explain this using the table of reduction potentials. So looking at the table of reduction potentials, the reduction potential of copper is plus 0.33 v. The reduction potential of iron is -0.44 v. So copper, in this case, has a higher reduction potential. It preferentially wants to be reduced. Thus, the iron will be oxidized. So we can use these table of reduction potentials to determine if a reduction will occur. So let's see what happens when I add this zinc metal to the hydrochloric acid solution. You can see that the reaction is bubbling. We are producing hydrogen gas. So the zinc metal is being oxidized to zinc ions, and the hydrogen is forming hydrogen gas. If we look at the table of reduction potentials, we can see that the hydrogen preferentially wants to be reduced. So we're forming hydrogen gas, and the zinc is oxidized to zinc ions. We talk about electrochemical reactions, we often talk about oxidizing agents and reducing agents. The oxidizing agent is something that causes a species to be oxidized, and a reducing agent is something that causes a species to be reduced. So let's see the reaction when I take this copper metal and put it into a beaker containing silver nitrate solution. So you can see that when I place this copper into the solution, the color of the metal is changing. So which species is the reducing agent in this reaction? So in this reaction, the copper metal is the reducing agent. It's causing the silver ions to be reduced to silver metal, which you can see on the strip of copper here. They're depositing there on the surface. So remember that the agents are the reactants, and they're causing something to be reduced or oxidized.