1.3.3 GROUP 7

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Describe the melting and boiling points of group 7
from Cl-I the points increase // VdW increase in strength as increase in n of electrons
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Describe the reactivity of group 7
decreases down due to size// attraction of nucleus is less, shielding is more// are reduced to form -1 halide ions
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What happens when halogens react with each other?
more reactive will displace the lesser // displacement seen by colour change
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What is the colour of Cl water?
colourless
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What is the colour of bromine water?
Orange
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What is the colour of iodine water?
brown
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How can two different halogens be identified in a solution?
displacement// mix reaction mixture with organic solvent HEXANE // halogen displaced will dissolve to create solvent layer
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When forming a solvent layer, what colour is Cl?
pale yellow/ green
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When forming a solvent layer, what colour is Br?
orange/red
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When forming a solvent layer, what colour is I?
violet/ pink
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When do halogens undergo disproportionation reactions?
when reacted with cold dilute alkalis solutions (NaOH/ KOH) and chlorine with water
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What happens when chlorine is related with water?
disproportionation forms HCl and HClO
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What is produced when halogens react with cold dilute alkalis?
disproportionation // produces H2O, salt and an -ate
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how can halide ions be identified? describe the reaction
silver nitrate test // dilute nitric acid to remove interfering ions // add silver nitrate solution, produces silver halide precipitate
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What colour is a fluorine silver halide ppt?
no ppt formed, soluble in water
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What colour is a chlorine silver halide ppt?
white, will dissolve in excess dilute ammonia - NH3 to form a complex ion
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What colour is a bromine silver halide ppt?
cream // dissolves in conc ammonia
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what colour is a iodine silver halide ppt?
yellow, insoluble in ammonia
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Wh is chlorine used in water treatment?
Chlorate (I) ions kill bacteria // adding Cl or chlorite ions makes water safe// sterilises and kills harmful bacteria // makes taste and smell better
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What are the disadvantages of the use of chlorine in water treatment?
chlorine gas is toxic // chlorine reacts with compounds to from carcinogenic compounds (chlorinated hydrocarbons) // ethical considerations as people have no choice
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What are the pros and cons of fluoridated water?
PROS - prevents tooth decay CONS - link to increased risk of some bone cancers// in toothpaste so not really necessary
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Card 2

Front

Describe the reactivity of group 7

Back

decreases down due to size// attraction of nucleus is less, shielding is more// are reduced to form -1 halide ions

Card 3

Front

What happens when halogens react with each other?

Back

Preview of the front of card 3

Card 4

Front

What is the colour of Cl water?

Back

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Card 5

Front

What is the colour of bromine water?

Back

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