Module 2.1.5 - Redox Flashcards
What is oxidation number?
The number of electrons that an atom uses to bond with the atoms of another element
The sum of all oxidation numbers in a neutral compound is..
0
The sum of all the oxidation numbers in an ion is…
equal to the charge on that ion.
The oxidation number of any uncombined element is..
0
The oxidation number of oxygen in compounds is..
-2 (except in peroxides H2O2, O is -1)
The oxidation number of hydrogen in compounds is..
+1 (except in hydrides, bonded to a metal)
A group 1 element in an compound has a oxidation number of…
+1
A group 2 element in an compound has a oxidation number of…
+2
A group 3 element in an compound has a oxidation number of…
+3
What is the most electronegative element?
Fluorine (always -1)
What do group 7 elements have?
Varying oxidation numbers.
Assume is -1, unless asked to find
What do roman numerals represent?
the oxidation state of an element that can exist in more than one oxidation state (typical for transition metals, found in d-block)
What are oxyanions?
Negative ions containing oxygen and one or more other elements
What do the names of oxyanions normally end in?
‘-ate’
What do oxyanions aim for?
Lowest negative charge
What is the systematic name?
The word name of the compound, which can have the positive charge in roman numerals
What is redox?
A reaction where both oxidation and reduction take place?
What is oxidation?
Loss of electrons/an increase in oxidation number
What is reduction?
The gain of electrons/a decrease in oxidation number
How do you determine whether or not a reaction is redox?
- the changes in oxidation number of an element
- the transfer of electrons to/from an element
What does “OIL RIG” stand for?
Oxidation is loss (of electrons), reduction is gain (of electrons)
What do metals tend to do to form positive ions?
Lose electrons: undergo oxidation
What do non-metals tend to do to form negative ions?
Gain electrons: undergo reduction
What is an oxidising agent?
A reagent that oxidises (takes electrons from) another species; is reduced (electron acceptor)
What is a reducing agent?
A reagent that reduces (adds electrons to) another species; is oxidised (electron donor)
How do you construct a redox equation from half-equations?
Two half-equations must be combined
- multiply the half-equation(s) by a factor so number of electrons in each half-equation are the same
- add the two half-equations together, like pair of simultaneous equations
- electrons should cancel out, leaving redox equation
A2 ) How do you construct half-equations
1) Balance the element being oxidised or reduced
2) Balance the oxidation number: use ELECTRONS e-
3) Balance the charge using H+ (acid) or OH- (Alkali)
4) just add water to balance the O and H
