Group 7, The Halogens Flashcards
A student was reacting different halide ions with silver nitrate solution and studying the precipitates formed. Why did the student not bother testing fluoride ions?
Silver fluoride is soluble and so you don’t get a precipitate
What colour precipitate is produced when you react silver nitrate solution with iodide ions?
Pale yellow
What colour precipitate is produced when you react silver nitrate solution with chlorine ions?
White
What colour precipitate is produced when you react silver nitrate solution with bromine ions?
Cream
Give a simple ionic equation to show the reaction between silver nitrate solution and chlorine ions
Ag+(aq) + Cl-(aq) –> AgCl(s)
Give a simple ionic equation to show the reaction between silver nitrate solution and bromine ions
Ag+(aq) + Br-(aq) –> AgBr(s)
Give a simple ionic equation to show the reaction between silver nitrate solution and iodide ions
Ag+(aq) + I-(aq) –> AgI(s)
Give the reaction of chlorine with water to form chloride and chlorate ions
Cl2 + H2O HCl + HClO (chloric acid)
What type of reaction is that of chlorine with water? (ox, reduc etc)
Disproportionation
How could you test for the presence of chlorine?
Blue litmus turns red in the presence of chlorine (bleaches it)
Give the reaction of chlorine with water to form oxygen
2Cl2 + 2H2O –> 4HCl + O2
Give a use of chlorine in water
Forms bleach which sterilises water for swimming and drinking
Give a reaction to show the formation of bleach
Cl2 + 2NaOH –> NaClO (bleach) + NaCl + H2O
Describe and explain what you would observe if you added chlorine water to KBr
An orange solution is formed
Cl has displaced Br as it is a better oxidising agent, and so oxides Br- to Br2
Describe and explain what you would observe if you added chlorine water to KI
A brown solution is formed
Cl2 can oxidise the I- to I2
Describe and explain what you would observe if you added bromine water to KI
A brown solution is formed
Br2 can oxidise the I- to I2
Give an ionic equation to show the reaction between bromine water and KI
Br2 + 2I- –> 2Br- + I2
What kind of reaction is shown between the reaction of chlorine water and KBr
Displacement reaction
Also a redox reaction
What kind of reaction is shown between the reaction of chlorine water and KBr
Displacement reaction
Also a redox reaction
Describe and explain the trend in oxidising ability down the halogen ions
Decreases as you go down
Get larger - more shielding and so weakened nuclear attraction, resulting in the ion being less able to attract an electron (be reduced)
What type of reaction is the formation of bleach (ox/redox)?
Disproportionation
Why is dilute nitric acid added to a solution of halides in order to determine what ions are present?
to remove any other ions that could give undesired precipitates with silver nitrate
