23. 1 Redox reactions

Question 1

what are the 4 definitions for oxidation and reduction

Answer 1

oxidation:
* loss of electrons
* increase in oxidation number
* gain of oxygen
* loss of hydrogen
Reduction
* gain of electrons
* deccrease in oxidation number
* gain of hydrogen
* loss of oxidation

Question 2

define an oxidising agent

Answer 2

accepts electrons from another reactant and is itself reduced

Question 3

define reducing agent

Answer 3

A reducing agent donates electrons to another reactant and is itself oxidised

Question 4

half equations show …. so that …

Answer 4

electrons so that the chanreges on both sides can balance

Question 5

What is the sum of oxidation numbers?

Answer 5

Sum of oxidation numbers = total charge

Question 6

redox equation/reaction

Answer 6

A redox reaction is made up of an oxidation half-reaction and a reduction
half-reaction.

Question 7

how to write redox equation from half-equation

Answer 7

1. Balane the electrons: multiply each half equation by whatever necissary to have the same number of electrons on both
2. merge the two and calncel out the electrons
3. cancel out any species that are on both left and right hand side eg
   16OH -> 6OH becomes 10OH->

Question 8

how to write and balance an equation from oxidation numbers

Answer 8

1. write a summary overal equation
2. assign oxidation numbers to identify the atoms that change their oxidation numbers aka the one being reduced and the one being oxidised
3. balance only the specise being oxidised and reduced by using there change in oxidation number because that should always cancel eg
   S 0 -> +6 change +6
   N +5 -> +4 change -1 so we multiply this by 6
   best way is write them both as half equations and then scale factor and then merge
4. now balance the reamining species

Question 9

p

predicting products of redox reactions

Answer 9

aqueus redox reactions often form h20
other likley products are oh- and h+

Question 10

what can we use to balance half equations?

Answer 10

e- H2O H+

Question 11

Redox half equations may need to be balanced by either:

Answer 11

Balancing the charges by adding electrons

Adding H+ ions to reduce some oxidising agents (includes the
addition of water)

Question 12

reduction of Cr +6-> +3 brings about a colour change of

Answer 12

orange to green

orange has 6 letters

Question 13

to balance a half equation first add … then finally balance with …

Answer 13

H+ then e-