oxidation, reduction, redox equations Flashcards
What is oxidation?
The loss of electrons or gaining of protons
What is reduction?
The gaining of electrons or loss of protons
What is in an oxisdising agent?
A species that is an electron acceptor and removes electrons from another species
What is a reducing agent?
Species that is an electron donator and gives electrons to another species
What is a disproportionation reaction?
When a species is oxidised and reduced simultaneously
What is an oxidation state?
The hypothetical charge on an element in a compound or ion
What is the oxidation state of an element?
Always 0
What must the sum of all the oxidation states in the compound vehicle to?
0 or the overall charge on an ion
Which groups in the periodic table have fixed oxidation states and what are they?
Group 1 = +1
Group 2 = +2
Group 3 = +3
What is the oxidation state of hydrogen usually?
+1
What is the oxidation state of hydrogen in metal hydrides? (e.g., NaH)
-1
What is the oxidation state of fluorine?
always -1
What is the oxidation state of halogens? What is the rule for working out the oxidation state?
- usually -1
- unless another element in the compound is more electronegative (e.g., ICl = +1 -1)
What is the oxidation state of oxygen usually?
- 2
What is the oxidation state of oxygen in peroxides? (e.g., H2O2)
-1
How do you work out the oxidation state of an ion?
The oxidation state will be equal to the ions charge
What must the overall oxidation states in a molecular ion equal to?
The charge on the ion
What is the method for writing half equations?
- Calculate the oxidation states on each side of the equation
- Balance the elements changing the oxidation state
- Sort out the electrons
- Sort out the oxygens
- Sort out the hydrogens
- Check the total oxidation states are equal on both sides of the equation
How do you sort out the electrons when writing the half equation (step 3)?
- If the oxidation state becomes more negative, it gains electrons
- is oxidation state becomes more positive, it loses electrons
How do you sort out the oxygens writing a half equation (step 4)?
- For every oxygen gained you add one water molecule
- For every oxygen lost you remove one water molecule
How do you sort out the hydrogens when writing a half equations (step 5)?
- for every hydrogen atom gained, add one H + ion
- for every hydrogen at lost, remove one H+ ion
How do you combine half equations?
Adding equations together so that the electrons cancel out
How do you cancel out electrons when combining half equations?
Multiply each half equation to make the same number of electrons in each equation
