3.2.3 GROUP 7 Flashcards
What is the name of ClO-
- chlorate l
- hypochlorite
Name ClO3 -
Chlorate (v)
Name HClO
- chloric acid
- hypochlorus acid
Name NaClO
Sodium hypochlorite
State the reaction for chlorine with water (l)
- name products
Cl2 (g) + H2O ⇌ HCl (aq) + HClO (aq)
- produces hydrochloric acid
- produces chloric (l) acid
Describe Fluorine, chlorine, bromine, iodine at room temperature
F2 = yellow grass
Cl2 = green gas
Br2 = red/brown liquid
I2 = grey solid
State and explain the trend in boiling point down the group
- increases
- molecules increase in size, with more electrons
- these result in stronger induced dipoles between molecules
- therefore stronger VdW’s between molecules
State and explain the trend in electronegativity down the group
- atomic radius increases, meaning larger distance between electrons and the nucleus, weakening electrostatic attraction
- shielding increases, so inner electrons reduce the ability to attract electrons
What type of agent are halogens?
- oxidising agents, as they gain electrons to form a full outer shell
X + e ➡️ X-
State and explain the trend in reactivity down the group
- decreases
- atomic radius increases, electrons further from the nucleus
- shielding increases
- harder to attract an electron
State and explain the trend in oxidising power down the group, how does it relate to displacement ability
- decreases
- harder to attract electrons from other species
- halogens can therefore displace the halogen below it
State the products and observations in the following:
Cl2 + 2Br- ➡️
2Cl- + Br2
- chlorine oxidises bromine and displaces it
- solution will turn from green to orange
State the products and observations in the following
I2 + 2Cl- ➡️
I2 + 2Cl- (no change)
- iodine cannot displace chlorine, as it is less reactive
What type of agent are halides
- reducing agents
- must lose an electron to form a molecule
State and explain the trend in reducing ability down the group
- increases
- atomic radius + shielding increases, outer electron further away
- electrostatic attraction decreases, electron more easily lost
- species more easily oxidised
- State the products and observations for when chloride reacts with sulfuric acid, H2SO4
(Same reaction as fluoride)
NaCl + H2SO4 ➡️ - outline changes in Sulfur’s oxidation no.
➡️ NaHSO4 + HCl (g)
- misty white fumes observed
- S oxidation no. Stays at +6
State the products and observations for when bromide reacts with sulfuric acid, H2SO4
NaBr + H2SO4 ➡️
State products formed and observations in the further reduction
- potassium dichromate colour change?
- outline changes in sulfur’s oxidation no.
NaHSO4 + HI (g)
- misty white fumes
- further reduction
Br(g) + SO2 (g) + 2H2O
- orange vapour - potassium dichromate orange to green
- S oxidation no. = +6 to +4
State the products and observations for when iodine reacts with sulfuric acid, H2SO4
NaI + H2SO4 ➡️
State products and observations for further reduction
- potassium dichromate colour change?
- outline changes in sulfur’s oxidation n.
NaHSO4 + HI (g)
- misty white fumes
I2 (g) + SO2 (g) + 2H2O
- purple vapour - potassium dichromate orange to green
- further reduction
H2S (g) + 3I2 (g) + 2H2O
- rotten egg smell
- S oxidation no. = +6 to +4 to -2
How is HBr, HCl, HF, HI (g) observed?
Misty white fumes
How is SO2 (g) observed/tested
Potassium dichromate goes orange to green
How is H2S (g) observed/tested for
Rotten egg smell
Describe and explain the steps within the procedure to test for halides
- Acidify sample using nitric acid, HNO3, to remove carbonate ions, CO3 2-
- otherwise, CO3 2- will form white ppt w/ Ag+ (false positive) - Silver nitrate, AgNO3, added
State the observation for each halide when testing for halides
Cl - = white ppt
Br - = cream ppt
I - = yellow ppt
AgF = insoluble, dissolved
State further tests and their results to confirm the presence of a specific halide
- Add excess dilute NH3
Cl- = dissolves. Br- and I- = remain insoluble - Add excess concentrated NH3
Br- = dissolves. I- = remains insoluble
