Group 17 Halogens Flashcards

Flashcards covering the physical and chemical properties of Group 17 elements (halogens), their reactions, and their industrial and environmental significance.

What is another name for the Group 17 elements?

Halogens

What are the trends in colour and boiling point of halogens at room temperature as you go down the group?

The colours get darker, and boiling points increase.

Which halogen has the lowest melting and boiling points and is the most volatile?

Fluorine

What increases down Group 17, leading to stronger van der Waals forces?

The number of electrons and the size of the molecules increases.

Why does the reactivity of halogens decrease down the group?

It becomes harder to gain an electron due to increased electron shielding and atomic radius.

What are oxidizing agents?

Elements/compounds that gain electrons to oxidize another element/compound.

Out of chlorine, bromine, and iodine, which is the strongest oxidizing agent?

Chlorine

What is the general rule for displacement reactions involving halogens and halide ions?

A halogen will displace a halide from a solution if the halide ion is below it in the periodic table.

If chlorine is added to potassium bromide solution, what colour change will be observed?

Colourless to orange.

How do the halogens react with hydrogen, and how does reactivity vary down the group?

Fluorine reacts explosively, chlorine reacts with light/heat, bromine reacts with flame, iodine only partially reacts with constant heating.

What is thermal stability of a hydride?

How easily a hydrogen halide breaks up into its constituent elements when heated.

What is the trend in thermal stability of hydrides down Group 17, and why?

Thermal stability decreases down Group 17 due to weaker covalent bonds.

How do bond enthalpies of hydrogen halides change down Group 17, and why?

Bond enthalpies decrease down the group because the halogen size increases.

What reagents are used to test for halide ions?

Nitric acid, silver nitrate solution, and aqueous ammonia.

What precipitates are formed when silver nitrate is added to solutions containing different halide ions?

Fluoride - no precipitate, Chloride - white, Bromide - cream, Iodide - yellow.

How does the solubility of silver halide precipitates in ammonia vary?

Chloride - dissolves in dilute NH3, Bromide - dissolves in concentrated NH3, Iodide - insoluble.

What is observed when NaCl or NaF reacts with concentrated sulfuric acid?

Misty fumes of HF and HCl.

Describe the reaction of NaBr with concentrated sulfuric acid.

NaBr + H2SO4 produces HBr (misty fumes), then HBr + H2SO4 produces SO2 (choking gas) and Br2 (brown fumes).

Describe the reaction of NaI with concentrated sulfuric acid.

Nal + H2SO4 produces HI (misty fumes), then HI + H2SO4 produces SO2, which is further reduced to H2S (rotten egg smell) and I2.

What is a disproportionation reaction?

A reaction in which an element is both oxidized and reduced.

How does chlorine react with cold dilute and hot concentrated sodium hydroxide?

Chlorine reacts with cold dilute NaOH to form NaClO (bleach) and NaCl; with hot concentrated NaOH to form NaClO3 and NaCl.

Why is chlorine used in water purification?

Kills bacteria, prevents reinfection, prevents algae growth, removes tastes/smells, removes discoloration.

Why are Chlorine and chlorate ions industrially important?

Used to kill bacteria preventing disease

Describe applications and uses of PVC

It is very hard so it can be used for windows and drain pipes. Plasticiser can be added to make it more flexible

What are chlorofluorocarbons (CFCs)?

Halogenoalkanes in which all hydrogen atoms have been replaced by chlorine and fluorine.

What is the role of the ozone layer?

Absorbs UV radiation from the sun.

How do CFCs damage the ozone layer?

CFCs release chlorine free radicals which break down ozone into oxygen.