chapter 4 - redox reactions

Question 1

redox reaction

Answer 1

a reaction that involves the transfer of electrons from reductant to oxidant

Question 2

oxidation

Answer 2

• oxidation is loss
• reducing agents undergo oxidation
• reducing agents lose electrons (metals/ non-metal anions)
• electrons on right
• oxidising agent causes oxidation

Question 3

reduction

Answer 3

• oxidising agent undergo reduction
• oxidising agents gain electrons (non-metals/ metal cations)
• electrons on left
• reducing agents cause reduction

Question 4

oxidation numbers

Answer 4

represent charge if element were to completely lose or gain electrons
used to judge whether substance in undergoing oxidation or reduction
increase = oxidation
decrease = reduction

Question 5

oxidation number rules

Answer 5

1. pure element = 0
2. monatomic ion = charge
3. compound with O is -2 (make = 0)
   except OF2 +2 and H2O2 -1
4. compound with H is +1
   except group 1 hydrides H is -1
5. molecule, ON = 0
6. polyatomic ion = charge
7. in a compound, most electronegative atom is the negative

Question 6

balancing half equations in acidic solutions

Answer 6

1. balance all elements except H and O
2. balance O by adding H2O
3. balance H by adding H+
4. balance charge by adding electrons
   make sure they are on the correct side for the reaction
5. add state symbols

Question 7

overall redox reactions

Answer 7

1. write both
2. multiply so electron equal
3. add, cancel electrons
4. cancel H2O and H+ if they appear on both sides

Question 8

balancing half equations under alkaline conditions (obvious)

Answer 8

1. balance all elements except H and O
2. balance Hydroxide ions by adding OH-
3. balance charge by adding electrons

Question 9

balancing half equations under alkaline conditions (unclear)

Answer 9

1. balance as fro acidic
2. add OH- on both side to neutralise H+
3. combine H+ and OH- to make H2O
4. cancel H2O