3.2.3.1 Trends in Properties Flashcards
What are the 4 main halogens?
Fluorine
Chlorine
Bromine
Iodine
How do you usually find the halogens?
Diatomic F2 Cl2 Br2 I2
What is the trend in Boiling Points?
- Increases going down the group
- This is due to the increasing number of VdW/London forces as there is an increased number of electrons
What is the trend in electronegativity?
- Decreases going down the group
- Smaller atoms attract electrons more compared to larger ones
- Due to less shielding as they have more inner electrons
What is the trend in Atomic Radius?
- Increases going down the group
- There are more shells in the atom which increases the size of it
What is the trend in Ionisation Energies?
- Decreases going down the group
- Force of Attraction between nucleus and outermost electron decreases due to the increases in molecule size
What is Oxidation Power?
A molecule ability to gain an electron causing the reacting molecule to be oxidised
What is the trend in Oxidation Power?
- Decreases going down the group
- Molecules get larger and due to shielding so they can less easily gain an electron
How do you test for Oxidation Power?
-Displacement reaction between halides and a diatomic halogen
-All halogens will displace a halide if it is below it in the periodic table
Does Cl2 displace KBr
Yes - produces Br2 which is an orange solution
Does Br2 displace KCl
No - Cl has a greater oxidisation ability
Does Cl2 displace KI
Yes - produces I2 which is a brown solution
Does Br displace KI
Yes - produces I2 which is a brown solution
Does I2 displace KBr or KCl
No
What is Reducing Power?
A molecule ability to lose an electron causing the reacting molecule to be reduced
What is the trend for Reducing Power?
- Increases going down the group
- Molecules get larger and due to shielding so they can m,ore easily lose an electron
How to test for Reducing Power?
- You can test them via a reaction with sulfuric acid
What happens in the reaction with NaF/NaCl with H2SO4?
NaF/Cl + H2SO4 –> NaHSO4 + HF/Cl
O.S of halide and sulfur remain the same (-1 and +6)
What happens in the reaction with NaBr with H2SO4?
NaBr + H2SO4 –> NaHSO4 + HBr
Further redox reaction due to higher reducing power
2NBr + H2SO4 –> 2H2O+ SO2 + Br2
O.S of Bromide goes from -1 to 0 and Sulfur goes from +6 to +4
What happens in the reaction with NaI with H2SO4?
NaI + H2SO4 –> NaHSO4 + HI
2HI + H2SO4 –> 2H2O+ SO2 + I2
Reacts again to form H2S which smells like rotten eggs
6HI + SO2 –> H2S + 3I2 + 2H2O
What is the procedure to test for Halides?
- Add Dilute Nitric Acid to remove any ions which might interfere with the reaction
- Add a few drops of AgNO3
- A precipitate is formed
What is the result of Fluorine with Silver Nitrate?
No precipitate
What is the result of Chlorine with Silver Nitrate?
White precipitate
What is the result of Bromine with Silver Nitrate?
Cream precipitate
What is the result of Iodine with Silver Nitrate?
Yellow precipitate
What is the trend when you add Ammonia to a Halide?
-Decreases in solubility
-Each halide has a different solubility
