CH 12 Flashcards
(15 cards)
How does oxidizing power vary down the halogen group?
Decreases ↓ the group: F₂ > Cl₂ > Br₂ > I₂
Why does oxidizing strength decrease down the group?
Atomic size increases, outer electrons are farther from the nucleus → less attraction for electrons = weaker oxidizing ability.
How do halogens react with hydrogen?
They form hydrogen halides: H₂ + X₂ → 2HX (e.g., H₂ + Cl₂ → 2HCl)
Which halogen reacts most vigorously with hydrogen?
Fluorine reacts explosively, chlorine in sunlight, bromine needs heating, iodine reacts partially when strongly heated.
Why does reactivity decrease down the group in hydrogen reactions?
Bond strength of H–X increases and halogen reactivity decreases.
Which hydrogen halide is most thermally stable?
HF > HCl > HBr > HI
Why does thermal stability decrease down the group?
H–X bond weakens due to larger atomic size → easier to break with heat.
Which halide ion is the strongest reducing agent?
I⁻ > Br⁻ > Cl⁻ > F⁻
Why does reducing ability increase down the group?
Larger ions lose electrons more easily due to lower nuclear attraction.
What happens when AgNO₃ is added to halide ions?
Precipitates: Cl⁻ = white (AgCl), Br⁻ = cream (AgBr), I⁻ = yellow (AgI)
How to distinguish between AgCl, AgBr, AgI?
Use NH₃: AgCl dissolves in dilute, AgBr in conc., AgI doesn’t dissolve.
What happens when halides react with conc. H₂SO₄?
NaCl → HCl gas; NaBr → HBr + Br₂ + SO₂; NaI → HI + I₂ + H₂S
Which halides act as reducing agents in this reaction?
Br⁻ and I⁻ reduce H₂SO₄ to SO₂, H₂S, or S.
How does chlorine disinfect water?
Cl₂ + H₂O ⇌ HCl + HOCl; HOCl ⇌ H⁺ + OCl⁻
What is the role of HOCl and OCl⁻?
Both are oxidizing agents that kill bacteria by destroying cell structures.
