Unit 5 - Halogens
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State and colour of fluorine at room temperature
Pale yellow Gas
State and colour of chlorine at room temperature
Very pale green Gas
State and colour of bromine at room temperature
Red / brown Liquid
State and colour of iodine at room temperature
Purple / black Solid
State and colour of astatine at room temperature
Black Solid
Difference between hydrogen chloride and hydrochloric acid
Hydrogen chloride is a gas, and has the formula HCl(g). When hydrogen chloride dissolves in water, hydrochloric acid is formed. This has the same formula, but you can tell the difference because of the state symbol (aq), which stands for ‘aqueous’.
Why is hydrogen chloride acidic in water but not methylbenzene
When hydrogen chloride gas dissolves in a solvent like methylbenzene, the molecules do not split up. A solution of HCl in methylbenzene does not contain hydrogen ions, so it is not acid
Describe an experiment to show a more reactive halogen will displace a less reactive halogen from a solution of one of its salts
Add the halogen to the solution, a colour change will indicate a displacement. Eg. Sodium bromide (clear) + chlorine (vv pale green) would make sodium chloride (clear) + bromine (brown)
What is another term for displacement reaction
Redox
Test for the anion Cl-
Use dilute nitric acid and silver nitrate solution. A white precipitate is formed
Test for anion Br-
Use dilute nitric acid and silver nitrate solution. A cream precipitate is formed
Test for anion I-
Use dilute nitric acid and silver nitrate solution. A yellow precipitate is formed
Simple test for chlorine gas
Makes damp blue litmus paper turn red, then bleaches it white
What group is also known as the halogens
Group 7 (fluorine, chlorine etc)