Reactions of halogens

Question 1

trend in reactivity in group 7

Answer 1

decreases down the group

opposite to group 1

Question 2

what halogens produce when they react with metals

Answer 2

compounds

metal halides

(sodium + chlorine -> sodium chloride)
sodium burns with an orange flame and forms white sodium chloride

Question 3

an example of a metal halide reaction

Answer 3

iron + chlorine -> iron chloride

iron burns to form a dark purple solid

Question 4

halide ions

Answer 4

have a 1- charge

compounds of metals or hydrogen with halogens

Question 5

Explain the trend in reactivity going down the group

Answer 5

• decreases
• the less easily an electron is gained the less reactive it is

going down group 7:

• outer shell gets further from the nucleus
• more shielding by inner electrons

-force of attraction between positive nucleus and negative outer shell electrons weakens

• electrons are gained less easily
• atom is less reactive

Question 6

Hydrogen reacts vigorously with bromine vapour to produce hydrogen bromide gas:

H2 (g) + Br2 (g) -> 2HBr (g)

What pH solution does it form when it dissolves in water?

Answer 6

acidic solution

hydrogen halides all dissolve in water to produce acidic solutions

Question 7

Cold iron wool burns in fluorine but hot iron wool reacts slowly with iodine vapour

Explain why iodine is less reactive than fluorine

Answer 7

• outer shell in iodine is further from the nucleus
• more shielded by inner electrons than fluorine
• attractive force is weaker as there is more distance between the positive nucleus and the negative outer electrons
• this causes iodine to gain electrons less easily than fluorine does

Question 8

Aluminium powder reacts vigorously with iodine to produce aluminium iodide, AlI3

Write a balanced equation for the reaction

Answer 8

2Al + 3I2 -> 2AlI3

Question 9

Describe how hydrochloric acid is formed

Answer 9

H2 + Cl2 -> 2HCl
hydrogen + chlorine -> hydrogen chloride

• hydrogen and chlorine molecules collide
• covalent bonds that hold the atoms together break
• hydrogen and chloride atoms form a covalent bond
• forms hydrogen chloride

-when hydrogen chloride dissolves in water the molecules break up into atoms

• H+ and Cl-
• H+ ions make the solution acidic

-hydrochloric acid is formed