What is oxidation?
- gain of oxygen, gain of hydrogen and loss of electrons
What is reduction?
The loss of hydrogen and oxygen and gain of electrons
What is O.S of elements?
0
What is the O.S. of oxygen in a compound?
-2 except in peroxides it is -1
What is the O.S. of H ?
+1 except in metal hydrides it is -1
What is the O.S. of a neutral compound?
O
Work out the O.S. of S in SO42-?
+6
Work out the O.S. of Cr in K2Cr2O7
+6
What is the rule for O.S. in polyatomic ions?
The sum of all O.S. should equal the charge on the ion
How to write net ionic equations?
- Write the molecular equation
- Write the full ionic equation
- Cancel out spectator ions
How to calculate redox titrations for acid solutions?
- Balance for atoms other than H or O
- Balance for O by adding H20
- Balance for H by adding H+
- Balance for the charges by adding electrons
Balance the equation Fe2+ + MnO4- —FE3+ + Mn2+
What does the reactivity series tell us?
The ease the metals undergo oxidation ( top being more likely to be oxidised)
What can metals above hydrogen do?
the displace the H+ ions to form H2
What does in an increase for an oxidation state of a metal show?
The element is oxidised ( it is a reducing agent)
What are the features of electrolytic cells?
- split ionic compounds into their constituent elements through an electrical current
- has the positive electrode being the anode and the negative being the cathode
- from electrical to chemical energy
- endothermic
- non spontaneous
How is the electrical current conducted?
- electron flow in the wires and the movement of ions in the electrolyte
What are the features of the voltaic cell?
- Spontaneous redox reaction
- positive electrode is the cathode and the negative electrode is the anode
- from chemical to electrical energy
- electrons flow from anode to cathode
