Group II - Halogens

Question 1

what does halogen mean?

Answer 1

salt maker : this is because they react with most metals to form salts

Question 2

why does their reactivity decrease down the group?

Answer 2

as the atom gets bigger, an eighth electron will be further from the attractive forces of the nucleus. this makes it harder for the atom to gain this electron

Question 3

reaction with water observation

Answer 3

the halogens dissolve in water and also react with it, forming solutions that behave as bleaches

chlorine solution is pale yellow

bromine solution is orange

iodine solution is yellow/ brown

Question 4

equations for halogens and water

Answer 4

chlorine + water —> hydrochloric acid + chloric (I) acid

Cl,2 + H,2O —> HCl + HClO

Question 5

metals and halogens: observations

Answer 5

form salts with all metals.

with a metal such as iron, brown fumes of iron (III) chloride form

Question 6

metals and halogens - equations

Answer 6

fluorine forms salts called fluorides

chlorine forms salts called chlorides

bromine forms salts called bromides

iodine forms salts called iodides

Question 7

displacement reactions: halogens

Answer 7

• more reactive halogen will displace a less reactive halogen from a solution of salt
• chlorine displaces bromine from sodium bromkde, the colourless solution turns orange when chlorine is added due to the formation of bromine
• chlorine displaces iodine from sodium iodide solution, the colour solution turns brown when chlorine is added due to the formation of iodine

Question 8

uses of halogens

Answer 8

• fluorides - in toothpaste
• fluorine compounds: in teflon pans
• chlorine: purifies water
• chlorine compounds: household bleaches
• iodine solution: an antiseptic

Question 9

chlorine, bromine and iodine colours

Answer 9

at room temp: chlorine is pale green

bromine is red brown

iodine is a black solid (brown in solutions)

Question 10

states at room temp

Answer 10

fluorine : gas

chlorine: gas
bromine: liquid
iodine: solid

Question 11

why is chlorine used in the treatment of drinking water?

Answer 11

it purifies water

Question 12

which halogen has medical uses?

Answer 12

iodine as an antiseptic

Question 13

fluorine is used to make a plastic material called teflon - what is teflon used for?

Answer 13

coating pans to make them non-stick

Question 14

what can hydrogen do with halogens?

Answer 14

react to form hydrogen halides (hydrogen chloride…. hydrogen bromide)

Question 15

what happens when hydrogen chloride is dissolved in water?

Answer 15

the HCl molecules split up into H plus and Cl minus ions and form a solution called hydrochloric acid

this process is called dissociation

it is acidic because it contains H+ ions

Question 16

properties of halogen

Answer 16

• low boiling points

- poor conductors of heat and electricity