Flashcards
Redox equations and electrode potentials
Cards in this deck (28)
- 1Define redox reactionsWhen molecules/ atoms involved in a reaction are both oxidised and reduced
- 2TOP TIP!Oxidation states and oxidation numbers are the same thing
- 3Name some of the rules that you know about oxidation numbers-Elements have ON of 0
- Monoatomic ions always have same ON as their charge
-H in metals are -1 and in non metals are +1
... - 4TOP TIP!The roman numerals in the name of a chemical shows its OXIDATION NUMBER!
- 5What are the steps to balancing redox equations in acidic conditions?1) Write out the half equations
2) Balance atoms that aren't O or H
3) Balance O by adding H2O then balance H by adding H+
4) Before combining, make sure both half equations have the same number of electrons
5) Combine half equations, cancel out species
Then you have your balanced redox equation - 6What are the additional steps for finding the balanced redox equations in alkaline conditions?1) Write out the half equations
2) Balance out the masses/ moles (If needed add H+ ions to balance H and O atoms for O...H2O)
3) Balance the charges using electons
4) Before combining, make sure both half equations have the same number of electrons
5) Combine half equations, cancel out species
Then you have your balanced redox equation
6* Add OH- to both sides of the equation ( let it react with the excess H+ to form water)
Then cancel out your extra water with some of the product water molecules - 7Try balancing the reaction when Zinc metal displaces silver ions from silver nitrate to form zinc nitrate and silver metalYou can do it!
Zn + 2Ag---> Zn2+ + 2Ag - 8TOP TIPOxidant is another way of saying oxidising agent
- 9What are the purposes of cells?The quantify the reactivity of elements.
They give you a sense of how much more/less reactive an element is - 10What is the importance of voltmeters? Why do they need to be high resistantThey measure the difference between how much force the electrons coming in have, compared to how much force is sucking the electrons away
-They need to be resistant to lower the current, so that electrons don't flow from anode to the cathode; we want the electrons to stay where they are so that the difference is charge can be measured - 11What is the purpose of the salt bridge?-To complete the circuit by connecting two half cells
-To prevent the precipitation and changes in concentration of the salts, which could affect the EMF - 12What is the EMF?This is the difference in elecrtode potential between two standard cells
- 13What is the definition of the hydrogen electrodeThis is the cell that has a standard electrode potential of 0.00V
It is used as a reference for all the other elements - 14What actually is a standard electrode potentialIt is the difference in electrode potential compared to a standard hydrogen electrode under standard conditions of 1moldm-3, 1 atm and at 25 degrees
- 15DON'T FORGET!-When writing half equations, make sure the electrons are on the left, and you equation makes sense
-Never forget the signs on your EMF! - 16What can the E cell tell you?The more positive the E cell, the stronger the oxidising agent
The more negative, the stronger the reducing agent - 17Identify the oxidising and reducing agent when Iron(ii) chloride reacts with chlorine to produce iron(iii) chlorideIron is reducing agent
Chlorine is oxidising agent - 18Iodine and Chlorine react together in a two step reaction. Identify which species is reduced and which oxidised I2 + Cl2 -> 2ICl 2ICl + 2Cl2 -> I2 Cl6It may be handy to remember that the more reactive is likely to get it's way. We know that the halogens decrease reactivity down the group so Chlorine is more reactive so it is more likely to be reduced so Iodine is more likely to be oxidised
- 19Balance the equation: Fe+ + Cl2 --> Fe+ +Cl-2Fe2+ + Cl2 -> 2Fe3+ + 2Cl-
- 20What skills does Potassium manganate have?It's little party trick is that it is able to reduce Fe2+ to Fe3+
- 21Why must potassium manganate solution be acidified?This provides a SOURCE of hydrogens to form water with the soon to be abandoned O in MnO4-
- 22TOP TIPIf you are trying to balance the number of electrons between the two half equations, but the multiplier is not a whole number.....DONT FORGET that you can use one number for one equation and another for the other
- 23Do you know how to relate the electrode potential to the position of the equilibrium?-The more positive the standard E potential the more shifted to the right the equilibrium.
Think about it.... the more positive, the more easily it forms metals, via gaining electrons so the more shifted to the right the reduction direction equation is and the less electrons built up on the electrode so the more positive - 24Explain why the standard electrode potential of Mg is negative-Magnesium has a great tendency to form positive ions than the Hydrogen atoms, so the equilibrium if shifted further to the left than the hydrogen electrode
-This means that more electrons build up on the mg electrode meaning that it is more negative - 25How can you tell which ion is easiest to convert into the metal from the standard electrode potentials?The more positive, the more shifted to the right the equilibrium, so the more easily the metal is formed
- 26How do you draw the conversion method of the standard electrode cell?Pt [H2] g / 2H+aq <-> Mg2+aq / Mg s
- 27TOP TIPThings not to forget about:
-The hydrogens when balancing
-Start off balancing with the main atom
-How to balance the charges - 28—
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- A level Chemistry Flashcards on Redox equations and electrode potentials, created by Sparkle Shine on 24/02/2018.
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