2.1.5 Redox Flashcards
What’s oxidation a gain of (1) and a loss of (2)
Gain of oxygen
Loss of hydrogen
Loss of electrons
What’s reduction a loss of (1) and a gain of (2)
Loss of oxygen
Gain of hydrogen
Gain of electrons
What happens to magnesium as it burns in oxygen
What happens to the oxygen
Gets oxidised (gains oxygen & loses 2e-)
Oxygen gets reduced (gains 2e-)
Why are they called redox reactions
As oxidation can’t occur without a reduction also occurring
How do we show electrons gained/lost in redox
By splitting the full equation into 2 half equations
1 shoes oxidation
1 shows reduction
What electrons are always on the left of the arrow in half equations
The gaining electron
What reactions are redox in disguise
Displacement reactions
What does an ionic equation show
The ions that take part
4 halogens and their halides
Fluorine, F2 - Fluoride, F-
Chlorine, Cl2 - Chloride, Cl-
Bromine, Br2 - Bromide, Br-
Iodine , I2 - Iodide, I-
What do group 7 elements switch between in redox
The halogen form and halide form
How can we decide which species is being oxidised or reduced if the reactions doesn’t involve oxygen/hydrogen
By observing the electron transfer
What are the 6 oxidation state rules
- Elements always zero
- Group 1,2,3 metals always charge an ion
- Hydrogen is +1 except when with group 1,2,3 metals (is -1)
- Oxygen is -2 except when peroxide (is -1)
- In neutral compounds the OS must add up to 0
- In more complex ions the oxidation state must add up to the charge on the ion
What must OS state add up to in neutral compounds
0
What must the OS add up to in more complex ions
The charge of the ion
What has happened to the element if the OS state goes up
Oxidised
If the OS goes down what happens to the element
It’s reduced
What’s a reducing agent
Gives away electrons (electron donor)
What’s an oxidising agent
Removes electrons (electron acceptor)
What must an oxidising agent become itself
Reduced
What must a reducing agent become itself
Oxidised
How can a half equation be made
Splitting a full equation
5 rules for half equations
- Balance atoms undergoing redox
- Balance oxygens by adding water
- Balance hydrogens by adding H+
- Balance charges by adding/subtracting electrons
- Add state symbols
When half equation reactions are carried out, what conditions are used and why
Under acidic aqueous conditions
Acid provides H+ ions
Aqueous medium provides water
What makes up a full redox equation
A reduction half-equations being added with an oxidation half-equation
What must cancel out when making a full redox equation
The electrons when the 2 are added together
What should you do if number of electrons doesn’t match
Multiply to find a common number
What’s oxidised and reduced in a MASH reaction
Metal - oxidised
Hydrogen - reduced
What do we use to tell us oxidation number
Roman numerals
What do compounds ending -ate contain
Oxygen and another element
