Group 7 Flashcards

Active recall practice for properties, displacement, reactions with sulfuric acid, and testing halide ions.

Trends & Reactivity: read all 5 questions and answers

State the trend in the boiling point of halogens down Group 7 and explain why.
Increases: molecular size and number of electrons increase, making the van der Waals forces between molecules stronger.
Why does the electronegativity of halogens decrease down Group 7?
Atomic radius and shielding increase, weakening the electrostatic attraction between the nucleus and the bonding pair of electrons.
State the trend in the oxidising ability of the halogens down Group 7.
Decreases (Fluorine is the strongest oxidising agent, Iodine is the weakest).
Why does the oxidising ability of the halogens decrease down Group 7?
Atomic radius and shielding increase, meaning the nucleus has a weaker attraction for incoming electrons, so they are gained less easily.
State the trend in the reducing ability of the halide ions down Group 7.
Increases (Iodide is the strongest reducing agent, Fluoride is the weakest).

Displacement & Redox Reactions: read all 5 questions and answers

Write the ionic equation for the reaction that occurs when chlorine gas is added to potassium bromide solution.
Cl₂(aq) + 2Br⁻(aq) → 2Cl⁻(aq) + Br₂(aq).
Describe the colour change when chlorine gas is bubbled through a solution of potassium iodide.
The colourless solution turns brown (due to the formation of iodine, I₂).
Write the ionic half-equation showing the reduction of chlorine to chloride ions.
Cl₂ + 2e⁻ → 2Cl⁻.
Why will bromine not displace chloride ions from a solution of sodium chloride?
Bromine is a weaker oxidising agent than chlorine, so it cannot oxidise chloride ions.
Which halogens can displace iodide ions from an aqueous solution of sodium iodide?
Chlorine and bromine (both are stronger oxidising agents than iodine).

Reactions with Concentrated Sulfuric Acid: read all 5 questions and answers

Write the chemical equation for the reaction of solid sodium chloride with concentrated sulfuric acid.
NaCl(s) + H₂SO₄(l) → NaHSO₄(s) + HCl(g).
What type of reaction occurs when sodium chloride reacts with concentrated sulfuric acid, and what is observed?
Acid-base reaction (no change in oxidation state); observed as steamy white fumes of HCl.
When sodium bromide reacts with concentrated sulfuric acid, orange fumes are produced. Identify these fumes and write the half-equation for their formation.
Bromine gas (Br₂); half-equation: 2Br⁻ → Br₂ + 2e⁻.
Name the gas with a choking smell produced when sodium bromide reduces concentrated sulfuric acid, and state the oxidation state of sulfur in this gas.
Sulfur dioxide (SO₂); oxidation state of sulfur is +4.
Identify the three reduction products formed (excluding water) when sodium iodide reacts with concentrated sulfuric acid.
Sulfur dioxide (SO₂ - choking gas), sulfur (S - yellow solid), and hydrogen sulfide (H₂S - rotten egg smell).

Halide Tests & Water Treatment: read all 5 questions and answers

Describe how you would test a solution for halide ions.
Add dilute nitric acid (HNO₃) to remove impurities, then add silver nitrate (AgNO₃) solution.
Describe the colours of silver chloride, silver bromide, and silver iodide precipitates.
Silver chloride: white; silver bromide: cream; silver iodide: yellow.
How can dilute and concentrated ammonia be used to distinguish between silver halide precipitates?
AgCl dissolves in dilute ammonia; AgBr dissolves only in concentrated ammonia; AgI is insoluble in both.
Write the equation for the reaction of chlorine with water in the absence of sunlight.
Cl₂ + H₂O ⇌ HCl + HClO.
Write the equation for the reaction of chlorine with cold, dilute sodium hydroxide to make bleach.
Cl₂ + 2NaOH → NaCl + NaClO + H₂O.