chapter 10 - group 7, the halogens

Question 1

Give the two equations when sulphur dioxide (SO2) is formed from sulphuric acid (H2SO4) and hydrogen bromide/hydrogen iodide

Answer 1

2HBr(g) + H2SO4(l) = Br2(g) + SO2(g) + 2H2O(l)

2HI(g) + H2SO4(l) = I2(g) + SO2(g) + 2H2O(l)

Question 2

Given the equation when hydrogen sulphide (H2S) is produced when hydrogen iodide reacts with hydrogen sulphate (H2S04)

Answer 2

8HI(g) + H2SO4(l) = 4I2(g) + H2S(g) + 4H2O(l)

Question 3

Why does the melting and boiling points increase down group 7

Answer 3

The melting and boiling point increases down group 7 because the molecules become larger and they have more electrons therefore they have larger Vanderwaals forces and more energy is needed to break them. This increases the melting and boiling points of the group to halogens

Question 4

What happens to the reducing power down the halides

Answer 4

increases

Question 5

What happens to the oxidising strength down the halogens

Answer 5

Oxidising strength decreases down the halogens (F2/Cl2 are the best oxidising agents)

Question 6

Describe the trend in electronegativity down group 7

Answer 6

Electronegativity decreases down the group 7 as the atomic radius of the elements increases and shielding increases due to the number of shells present and inner electrons. The new place is therefore less able to attract the bonding pair of electrons

Question 7

write an equation for the formation of bleach from sodium hydroxide and chlorine

Answer 7

2NaOH + Cl2 = NaClO + NaCl + H2O

NaClO = bleach (sodium chlorate)

Question 8

Describe the observations and products formed when sodium or potassium chloride reacts with sulfuric acid

Answer 8

Effervescence, highly exothermic, misty steamy WHITE fumes that turn down blue litmus paper red.

HI formed along with K/NaHSO4

Question 9

Describe the observations and products formed when potassium bromide or sodium bromide reacts with sulphuric acid

Answer 9

Effervescence, highly exothermic reaction, steamy misty white fumes, turns litmus paper red

Orange vapours, choking gas

HBr, K/NaSO4, Br2, H2O, SO2

Question 10

Describe the observations and products formed when potassium iodide/sodium iodide reacts with sulphuric acid

In addition construct two equations to show how sulfur is formed

Answer 10

Effervescence, misty steamy white fumes, that turns litmus paper red

purple vapours(I2)
choking gas (SO2)
rotten egg smell (H2S)
yellow solid (S)

HI, K/NaSO4, SO2, H2O, I2, H2S, S,

two equations when sulfur is formed
KI(s) + H2SO4(l) = HI(g) + KHSO4(s/aq)
6HI(g) + H2SO4(l) = 4H2O(l) + 3I2(s) + S(s)

Question 11

Describe the appearance of flourine at room temperature and in water

Answer 11

At room temperature it is a pale green gas

Fluorine is too reactive so it doesn’t react and water. it doesn’t a fluoride ppt doesn’t form with nitric acid because AgF is soluble

Question 12

Describe the appearance of chlorine at room temperature and in water

Answer 12

At room temperature chlorine is a yellow/green gas

Chlorine in the water is a colourless/pale green colour

Question 13

Describe the appearance of bromine at room temperature and in water

Answer 13

At room temperature bromine is an orange brown liquid (l) or has orange vapours (g)

In water bromine is orange or yellow orange

Question 14

Describe the appearance of iodine at room temperature and in water

Answer 14

At room temperature iodine is a grey black solid (s)or has purple vapours(g)

In water iodine is an brown solution

Question 15

write the ionic equations for when silver nitrate reacts with a halogen

Answer 15

Ag+(aq) + X-(aq) = AGX(s)

when the halogen doesn’t dissolve in NH3

AgBr(s) + 2NH3(aq) = (Ag(NH3)2)+(aq) + Br-(aq)

AgI(s) + 2NH3(aq) = (Ag(NH3)2)+(aq) + I-(aq)