Group 7 Flashcards
Trend of electronegativty down group 7
The further down the group, the lower the electromagnetically, more shielding, further from nucleus
Trend in atomic radius down group 7
Further down, atomic radius increases
Trend in melting/boiling points down group 7
Further down, melting and boiling point increases as each molecule as more electrons, increasing Van Der Waals forces. This occurs due to them being diatoms
Trend of oxidising ability down group 7
Oxidising ability decreases down the group
Why would chlorine displace iodide ions
Chlorine is a better oxidising agent than iodine
Trend of reducing ability down group 7
Reducing ability increases as you go down the group.
Proof of the trend of reducing ability of group 7
Fluoride and chloride ions won’t reduce concentrated sulphuric acid
What is the test for halide ions
Add silver nitrate and nitric acid to a solution of the sample. Chlorine is white precipitate, bromine is cream, iodine is yellow
Why is silver nitrate solution used to identify halide ions
Silver Chloride, bromide and iodide are insoluble
Why is nitric acid used
The nitric acid reacts with, and removes, other ions that might also give a confusing precipitate with silver nitrate
Why can this test not be used for fluoride ions
Silver fluoride is soluble
Why is ammonia solution added after the silver nitrate test
To distinguish between silver bromide and silver iodide as they have similar colours
Observation with silver chloride and ammonia solution
Precipitate dissolves to give a colourless solution
Observation with silver bromide and ammonia solution
Dissolves in ->concentrated
Observation with silver iodide and ammonia solution
precipitate is insoluble in ammonia solution of any concentration
Reaction between chlorine and water without U.V. rays
Cl2 + H2O -> HClO + HCl
Why is chlorine used for water treatment
Humans are tolerant to small doses of chlorine. This allows water treatment plants to add chlorine to the process, killing microorganisms and making the water fit for human consumption.
Why would people agree with chlorine being used for water treatment
The benefits to health of water treatment by
chlorine outweigh its toxic effects
Reaction of chlorine with cold, dilute, aqueous NaOH
Cl2 + NaOH -> NaClO + NaCl + H2O
Uses of sodium hypochlorite (NaClO)
NaClO is used as bleach and for water purification
Reaction between chlorine and water with U.V. rays
2Cl2 + 2H2O -> 4HCl + O2
What is the main product when chlorine reacts with concentrated sulphuric acid and how to know it’s produced
HCl, misty why fumes with H2O in the air
What is the main product when bromine reacts with concentrated sulphuric acid and how to know it’s produced
HBr, misty white fumes with H2O in the air
Br2, brown vapour
What is the main product when iodine reacts with concentrated sulphuric acid and how to know it’s produced
HI, misty white fumes with H2O in the air
I2, purple vapour
H2S, rotten egg smell
