SEARCH
You are in browse mode. You must login to use MEMORY

   Log in to start

level: Oxidation and Reduction, and Electrolysis

Questions and Answers List

level questions: Oxidation and Reduction, and Electrolysis

QuestionAnswer
What does Oxidation mean?-Reaction with Oxygen -Adding Oxygen to a Substance -Removing Electrons
What does Reduction mean?-Removing Oxygen -Adding Electrons
Take Fe²O³ + 3CO ---> 2Fe + 3CO² Which is here Reduced, and Oxidised [Terms of Oxygen]-Iron Oxide becomes Iron. Iron Oxide is Reduced -Carbon Monoxide becomes Caron Dioxide. Carbon is Oxidised
What does a Redox Reaction mean?-Simply means Oxidation and Reduction takes place in the Same Reaction
What is an Oxidising Agent?-This is something that takes Electrons, therefore being Reduced -This is something that Loses Oxygen, therefore being Reduced
What is an Reducing Agent?-This is something that Loses/Gains Electrons, therefore being Oxidised -This is something that Gets Oxygens, therefore being Oxidised
What do Half Equations show?-Simply show how Electrons move in a Reaction
Using Fe + 2H+ ---> Fe²+ + H² -Which one is the Oxidising Agent [Being Reduced] -Which one is the Reducing Agent [Being Oxidised]-Iron here is being the Reducing Agent. This is because it Loses electrons to the Hydrogen Ions. [Fe = Fe²+ + 2e-] -Hydrogen here is being the Oxidised Agent. This is because it Gains Electrons from the Iron atom [2H+ + 2e- --> H²]
Using Cu²+ + Mg ----> Cu + Mg²+ -Which element has been Reduced?1. Find out if each Element has Gained, or Lost Electrons by using Half Equations. [Cu²+ + 2e- ---> Cu] [Mg ---> Mg²+ + 2e-] 2. Reduction is Gaining Electrons, and in this case, its Copper.
What is Electrolysis? What happens?-This is simply Breaking down a Substance using Electricity -An Electric Current goes Through an Electrolyte, making it Decompose. -The Positive Ions, called Cations, go towards the Cathode, which is a Negative Electrode, making the Cations Reduced [Gain Electrons] -The Negative Ions, called Anions, go towards the Anode, which is a Positive Electrode, making the Anions Oxidised [Loses Electrons] -As the Ions become Uncharged, they becomes Discharged from the Solution
What is an Electrolyte?-Simply a Molten/Dissolved Ionic Compound
What is an electrochemical Cell?-This is a Circuit, that is made up of the -Anode -Cathode -Electrolyte -Power Source [Cell, Battery] -Wires connecting the 2 electrodes
Why can't Ionic Solids be Electrolysed? Why can Molten Ionic Compounds?-This comes back to the fact that the Ions are in Fixed Positions, and so Cant Move. No Movement = No Electricity -Molten Ionic Compounds can, because the Ions can move Around. Movement of Charged Particles = Current = Electricity
What happens at the Cathode, and Anode?-The Positive Metal Ions gain Electrons [Reduced] to become Atoms at the Cathode [Cathode is Negative] -The Negative Ions lose Electrons [Oxidised] to become Atoms at the Anode [Anode is Positive]
Given an Example of what would happen with Lead Bromide in terms of Electrolysis.-You would see Beads of Molten Leads being formed at the Cathode [Pb²+ + 2e- ---> Pb] Lead is being Reduced -You would see Brown Vapour, signifying Bromide Gas at the Anode. [2Br- ---> Br² + 2e-] Bromine is being Oxidised
What would be at the Cathode and Anode for: -Lead Iodide [PbI²] -Potassium Chloride [KCl] -Aluminium Oxide [Al²O³] Also give the Half Equations for each ElementLead Iodide: -Lead would be at Cathode [Pb²+ + 2e- --->Pb] -Iodine would be at Anode [2I- ---> I² + 2e-] Potassium Chloride -Potassium would be at Cathode [K+ + e- -->K] -Chloride would be at Anode [2Cl- ---> Cl² + 2e-] [Chlorine Gas] Aluminium Oxide: -Aluminium would be Cathode [Al³+ + 3e- ---> Al] -Oxygen would be at Anode [2O²- ---> O² + 4e-]
Is there any pattern with Electrolysis with Molten/Dissovled Ionic Compounds?-Yes -Metals /G1-2 go to the Cathode -Non-Metals go to the Anode
What can happen else in Electrolysis in Aqueous Solutions?-The Hydrogen Ions [H+] and the Hydroxide Ions [OH-] will also Form. -This change is Reversible
So what will happen if Electrolysis happens in an Aqueous Solution?-Not only will the Compound split in its Ions, but the Water will -The cathode will have the Metal Ions, and the Hydrogen Ions. -Hydrogen Gas will be made if the Metal is more Reactive than Hydrogen [Sodium] -A Solid layer of Pure Metal will be made, if Less Reactive than Hydrogen [Copper or Silver] -The Anode will have Molecules of Halide Ions [G7] if they are Present -If there is no Halide Ions, Oxygen will be made from the Hydroxide Ions
-What happens when Sodium Chloride is Dissolved in Water, and is being used for Electrolysis? How can you be sure of this?-4 Ions will appear. Na+, Cl-, OH- and H+ -Sodium is more Reactive than Hydrogen, so the Cathode will see Hydrogen Gas be made [2H+ + 2e- ---> H²] -This can be proven, by using the Squeaky Pop Test -Chlorine is a Halide Ion, so the Anode will see Chlorine Gas be made [2Cl- ---> Cl² + 2e-] -This can be Proven by using litmus Paper. Litmus Paper will become White if Chlorine is Present. [If Red for a moment, its because Chlorine is Acidic]
How can you set up an Electrochemical Cell? [Copper Sulphate]-Get 2 Inert Electrodes [Platinum or Carbon] and clean using Sandpaper -Make sure you don't touch it, as you can give Grease to it -Place both of the Electrodes into a Beaker that has your Electrolyte -Connect the Electrodes to a Cell/Battery via Wires
What happens to an Aqueous Solution of Copper Sulphate when Electrolysis takes place?-4 Ions appear. Cu²+, SO⁴²-, H+ and OH- -Copper is less Reactive than Hydrogen, so the Cathode sees Copper Metal being Formed. This coats the Cathode [Cu²+ + 2e- ---> Cu] -No Halide Ions are here, so Oxygen and Water is made. [4OH- --> O² + 2H²O + 4 e-] -This can be proven as Oxygen can Relight a Glowing Splint
What are Special about Non-Inert Electrodes-They can Decompose into the Electrolyte -Copper Electrodes are an Example
What happens if you use Copper Electrodes in an Electrolysis Reaction, using an Aqueous Solution of Copper Sulphate? What happens to the Masses?-Everything will seem the same, until you notice the Mass of the Anode Decreasing, and the Mass of the Cathode Increasing. -This is because Copper from the Anode, is Transferred to the Cathode -This can happen because the Electrical Supply makes the Electrons rip Away from the Copper atoms, in the Anode making them enter the Solution as Cu²+ -And then it gets Attracted to the Negative Electrode, which is the Cathode and it makes them back to Copper Atoms. -And Since Copper is less Reactive than Hydrogen, it will Stay There.