Topic 3 - Redox I Flashcards
What is oxidation?
When an element loses electrons or has an increase in oxidation number (OILRIG)
What is reduction?
When an element gains an electron or has a decrease in oxidation number (OILRIG)
What is an Oxidation number?
Oxidation numbers are numbers that are assigned to atoms or ions to show the extent to which they have been oxidised
What is the oxidation number of uncombined elements?
0
e.g Cl2, Fe etc.
What is the oxidation number of a neutral compound?
The sum of the oxidation numbers of all the elements in the compound = 0
e.g MgF2, Mg = +2 and F = -1
What is the oxidation number of ions?
The charge of the ion
e.g Cl- = -1, Fe2+ = +2, Fe3+ = +3
What is the oxidation number of complex ions (Ions containing more than one atom)?
The sum of all the oxidation numbers in the compound = charge of the ion
e.g NH4+, SO42-
What is the oxidation number of hydrogen in a compound?
+1
What is the oxidation number of hydrogen when bonded to a metal as a hydride?
-1
What is the oxidation number of oxygen in a compound?
-2
What is the oxidation number of oxygen when in hydrogen peroxide?
-1
What is the oxidation number of fluorine when in a compound?
-1
What is the oxidation number of metals in a compound?
It is positive and usually the same as the group number
What is the oxidation number of transition metals in a compound?
Transition metals are positive and have varying oxidation numbers
What is the oxidation number of non-metals in a compound?
It is negative with values up to that of the group number
What is a redox reaction?
A reaction in which both oxidation and reduction occur
Identify the atom that is reduced and the atom that is oxidised in the equation Mg + CuSO4 → MgSO4 + Cu using oxidation numbers
Mg - 0 → +2
Magnesium is oxidised
Cu - +2 → 0
Copper is reduced
Sulphate is the spectator ion and would not be included in the equation if it was ionic
Identify the atom that is reduced and the atom that is oxidised in the equation Cl2 + 2Br- → 2Cl- + Br2 using oxidation numbers
Cl2 - 0 → -1
Chlorine is reduced because it’s oxidation number decreases as it gains electrons
Br- - -1 → 0
Bromine is oxidised because it’s oxidation number increases as it loses electrons
Cl2 is the oxidising agent as it accepts electrons causing oxidation to occur
Br- is the reducing agent because it releases electrons causing reduction to occur
What is an ionic equation?
An ionic equation is an equation showing the reacting ions in a reaction and removes any spectator ions that remain in the same state
What is a half equation??
A half equation represents what happens to atoms/ions when they lose or gain electrons in reactions.
State the Oxidation state of Vanadium in VO2+
+5
State the Oxidation state of Chlorine in KClO3
+5
State the Oxidation state of Sulphur in H2SO4
+6
State the Oxidation state of Iodine in IF7
+7
State the Oxidation state of Nitrogen in HNO2
+3
State the Oxidation state of Chromium in CrO4 (2-)
+6
State the Oxidation state of Manganese in MnO2
+4
Name the compound CuSO4
Copper (II) Sulphate
Name the compound Fe(OH)2
Iron (II) Hydroxide
Give the formula of Iron (III) hydroxide
Fe(OH)3
Name the compound KMnO4
Potassium Manganate (VII)
Name the compound NF3
Nitrogen (III) Fluoride
Name the compound Cu(NO3)2
Copper (II) Nitrate (V)
What is a disproportionation reaction?
This is when the same element both increases and decreases it’s oxidation number
e.g 2H2O2 → 2H2O + O2
Oxygen from the hydrogen peroxide has been reduced from -1 to -2 in H2O and oxidised from -1 to 0 in O2
What is the reason for the use of Roman numerals when naming compounds and ions?
As it helps you to identify the charge on the elements/ions within the compound e.g Fe have 2 different charges 2+ or 3+
What is the definition of oxidation number?
Oxidation state shows the total number of electrons which have been removed from an element (a positive oxidation state) or added to an element (a negative oxidation state) to get to its present state.
