4.22 - Redox Reactions in Group 7 Flashcards
In groups 1 and 2, where are reactions the most vigorous?
At the bottom
In group 7, where are reactions the most vigorous?
At the top
What are the products of these redox reactions?
Ionic solids (salts) which are usually white
What does the halogen act as in all of these reactions?
An oxidising agent
In terms of electron transfer, what does this mean?
Electrons are transferred to the halogen
What is the change in oxidation number for the halogen?
0 to -1
What is the change in oxidation number for group 1 and group 2 metals respectively?
0 to +1 for group 1, and 0 to +2 for group 2
What can a reactive halogen do?
Replace a less reactive halogen from one of its compound
What type of reaction is this?
Displacement
What can chlorine displace?
Bromine and iodine
What can bromine displace?
Iodine
What can iodine displace?
Neither chlorine nor bromine
What type of solution do these reactions occur in?
Aqueous solutions
Thus, what are reactions indicated by?
A colour change
What is a problem with this fact?
The colour changes are very discrete, and the colours vary with concentration, making decisions about reactions hard to make
What is a solution to this?
Adding an organic solvent such as cyclohexane
Why?
Because the halogens are more soluble in organic liquids and so the colours are easier to distinguish
What broad type of reaction is a displacement reaction?
Redox reactions
What are the oxidation number changes for the more and less reactive halogens?
More reactive: 0 to -1
Less reactive: -1 to 0
What is a disproportionation reaction?
One in which a single element undergoes both oxidation and reduction
What happens when chlorine reacts with water?
HCl and HClO are formed
What happens when chlorine reacts with cold alkali?
Two salts and water are formed
Finish the equation: Cl2 + 2NaOH -> … … ….
NaCl + NaClO + H2O
What happens when chlorine reacts with hot alkali?
Two products and water are formed
Finish the equation: 3Cl2 + 6NaOH -> … … …
5NaCl + NaClO3 + 3H2O
