12.2 Reactions Of Group 17 Elements Flashcards
The rate of reaction ___ down the group 17
Decreases/becomes less vigorous because of the electronegativity of atoms
What is the evidence for the oxidising power of the halogens?
We can also judge the relative reactivity or oxidising power by looking at the displacement reactions with other halide ions in solutions. More reactive halogen can displace the less reactive halogen from a halide solution of the less reactive halogen.
The colours of halogen molecules and solution are difficult to identify positively in displacement reactions. How is this problem solved?
The halogens dissolve in the colourless liquid Cyclohexane, which is immiscible in water.
What is thermal stability?
The resistance of a compound to breakdown by heating
What is the bond energy decrease down group 17?
It is because elements with more electron shells have a longer bond length. the longer the bond lengthens, the less energy required to break it
The reactions of halide ions with sulphuric acid produces one or more toxic gases so they must be
Performed with great care in a fume cupboard
How to prepare hydrogen chloride
By dropping sulphuric acid slowly on crystals of sodium chloride. This will produce NaHSO4 and hydrochloric acid
Why cannot we use the same reaction that is used to produce hydrogen chloride in order to produce hydrogen bromide or hydrogen iodide?
Increasingly easy to compose hydrogen halides going down the group. When this happens the halide part of molecule in hydrogen bromide and hydrogen iodide is oxidised. Concentrated sulphuric acid is a relatively strong oxidising agent.
How does the oxidising of hydrogen halides happen?
First hydrogen bromide and hydrogen iodide formed in the same way as hydrogen chloride.
Then they oxidised with sulphuric acid to form iodine/bromine plus sulphur dioxide plus water.
Oxidation of iodine can also form sulphur or hydrogen sulphide instead of sulphur dioxide
What are some observations that can be made in the reactions of halide ions with sulphuric acid?
Sulphur is seen as a yellow solid
Hydrogen sulphide has a strong smell of bad eggs
Iodine is produced as purple vapour
What is disproportionation of chloride atoms
Redox reaction that happens when chlorine reacts with alkali. Some chlorine reduce and some oxidised in the same reaction
How does chlorine react with cold alkali(15 degrees)
Cl2+2NaOH—> NaCl+ NaClO+H2O
How does chlorine react with cold alkali(15 degrees)
Cl2+2NaOH—> NaCl+ NaClO+H2O
How does chlorine react in hot alkali?
Cl2+NaOH—> NaCl+ NaClO3+3H2O
The chemical equation for chlorination of water
Cl2(aq)+H2O—> HCl+ HClO
Why does the chlorination of water kill bacteria?
Chloric acid sterilises water by killing bacteria. Some of the chloric acid dissociates to produce ClO- which also acts as a sterilising agent
