ES - Inorganic chemistry and the periodic table *01

Question 1

what are halogens ?

Answer 1

highly reactive, non-metals of group 7

exist at RTP as diatomic molecules

Question 2

appearance and physical state at RTP - fluorine

Answer 2

pale yellow gas

Question 3

appearance and physical state at RTP - chlorine

Answer 3

yellow-green gas

Question 4

appearance and physical state at RTP - bromine

Answer 4

red-brown liquid

Question 5

appearance and physical state at RTP - iodine

Answer 5

shiny grey solid

Question 6

what happens to volatility as you go down group 7?

- and why

Answer 6

decreases

because of the increasing instantaneous dipole - induced dipole bonds
- these increase as the size and relative mass of the atoms increase

Question 7

what is volatility?

Answer 7

a measure of how easy it is to vaporise something (turn something from a liquid to a gas)

Question 8

what do halogens exist as diatomic molecules?

Answer 8

because they’re covalent and non-polar

Question 9

do halogens dissolve easily in water?

Answer 9

no

Question 10

do halogens dissolve easily in organic solvents?

Answer 10

yes

hexane

Question 11

colour in water - chlorine

Answer 11

virtually colourless

Question 12

colour in water - bromine

Answer 12

yellow / orange

Question 13

colour in water - iodine

Answer 13

brown

Question 14

colour in hexane - chlorine

Answer 14

virtually colourless

Question 15

colour in hexane - bromine

Answer 15

orange / red

Question 16

colour in hexane - iodine

Answer 16

pink / violet

Question 17

how do the halogens react?

Answer 17

react by gaining an electron in their outer p sub-shell. They are reduced, and are acting as oxidising agents

Question 18

what happens to reactivity as you go down group 7?

- why

Answer 18

decreases

because halogen atoms become larger as you go down the group so outer electrons further away from nucleus

outer electrons are shielded more from attraction of the +ve nucleus, because more inner electrons

this makes it harder for larger atoms to attract the electron needed to form an ion. so larger atoms are less reactive

Question 19

what is a displacement reaction?

Answer 19

a reaction where one reactant replaces another reactant in a compound

Question 20

what halogens will displace halide ions?

Answer 20

a more reactive halogen will displace a less reactive halide in solution

Chlorine displaces Br- and I-

Bromine displaces I-

Iodine will not displace either

Question 21

Half equation - Cl2 + KCl

Answer 21

no reaction

Question 22

Half equation - Cl2 + KBr

Answer 22

Cl2 (aq) + 2Br- (aq) –> 2Cl- (aq) + Br2

Question 23

Half equation - Cl2 + KI

Answer 23

Cl2 (aq) + 2I- (aq) –> 2Cl- (aq) + I2

Question 24

Half equation - Br2 + KCl

Answer 24

no reaction

Question 25

Half equation - Br2 + KBr

Answer 25

no reaction

Question 26

Half equation - Br2 + KI

Answer 26

Br2 (aq) + 2I- (aq) –> 2Br- (aq) + I2

Question 27

Half equation - I2 + KCl

Answer 27

no reaction

Question 28

Half equation - I2 + KBr

Answer 28

no reaction

Question 29

Half equation - I2 + KI

Answer 29

no reaction

Question 30

what happens if a reaction takes place?

Answer 30

colour change

Bromide displaced and bromine formed reaction mixture turns orange

Iodide displaced and iodine formed reaction mixture turns brown

Question 31

How can you make colour changes easier to see?

Answer 31

shake mixture with an organic solvent (hexane) the halogen present will dissolve in the organic solution which settles out a distinct layer above the aqueous solution

Question 32

how can you test for halide ions?

Answer 32

Add dilute nitric acid to remove ions that might interfere with reaction

then add silver nitrate solution (AgNO3)

and a precipitate of the silver halide is formed

Question 33

colour of halide percipitate in w/ Ag+ - Fluoride

Answer 33

no precipitate - it dissolves

Question 34

colour of halide percipitate in w/ Ag+ - Chloride

Answer 34

white

Question 35

colour of halide percipitate in w/ Ag+ - bromide

Answer 35

Cream

Question 36

colour of halide percipitate in w/ Ag+ - iodide

Answer 36

yellow

Question 37

the precipitates can be difficult to identify - how can you make this easier?

Answer 37

add ammoina solution

Question 38

what happens when add ammonia solution to: AgCl

Answer 38

precipitate dissolves in dilute ammonia soltion to give a colourless solution

Question 39

what happens when add ammonia solution to: AgBr

Answer 39

precipitate unchanged in dilute ammonia solution

precipitate dissolves in concentrated ammonia solution to give a colourless solution

Question 40

what happens when add ammonia solution to: AgI

Answer 40

precipitate does not dissolve

Question 41

Ionic equation of silver ions and halide

Answer 41

Ag+ (aq) + X- (aq) –> AgX (s)

where X- is the halide

Question 42

risks with transporting chlorine

Answer 42

its toxic and corrosive so must be kept away from eyes and skin, and harmful if breathed in (irritates respiratory system)

must be kept away from flammable materials (is an oxisiding agent so increases fire risks)

Question 43

how is chlorine transported

Answer 43

ususally kept as a liquid under pressure in small cylinders

Question 44

uses of chlorine

Answer 44

1. important part of water treatment - adding chlorine to water sterilises it, making it safe to drink or swim in
2. it kills disease-causing microorganisms
3. if we didn’t treat drinking water in this way we’de be at risk of getting all sorts of nasty and potentially dangerous infections
4. chlorine is also used to make bleach