Chapter 4 (4.3 Redox) Flashcards
Oxidation numbers of an uncombined element, combined oxygen, combined hydrogen, combined fluorine
Uncombined element= 0
Combined oxygen= -2
Combined hydrogen= +1
Combined fluorine= -1
The oxidation number exceptions
- when bounded to fluorine oxygen has an oxidation number of +2. In peroxides (hydrogen peroxide H2O2) oxygens oxidation number is -1
- when bonded to metals in hydrides hydrogen has an oxidation number of -1
Oxidation numbers in compounds
Overall charge is zero
Sum of oxidation numbers must equal 0
Define oxidation number
A measure of the number of electrons that the atom uses to bond with atoms of another element
Oxidation numbers in molecular ions
They have to add up the the charge of that ion
What does the Roman numeral mean in the name of the chemical
It represents the oxidation number
Eg in transition metals it shows which type foe example wether it’s fe3+ or fe2+
Eg in oxyanions (negative ions that contain an element and oxygen)
Define reduction
Loss of oxygen
Gain of electrons
Define oxidation
Gain of oxygen
Loss of electrons
What is a reducing and oxidising agent
Reducing agent = donated its electron
Oxidising agent = removed electrons from the other substance
What is oxidation and reduction in terms of oxidation numbers
Reduction = decrease in oxidation number
Oxidation = increase in oxidation number
How you construct a redox equation using half equations
Ensure the electrons have the same number in front, if not times the whole equation for them to match
Join the two equations and cancel any common things
Extra steps for constructing redox equation
- if reaction is carried out in acidic conditions and H+
- for alkaline add OH-
- if H and O are needed add H2O
What is disproportionation
When the same element gets both oxidised and reduced
