Physical properties of halogens
Which halogen has the lowest boiling point?
A. Chlorine
B. Bromine
C. Iodine
D. Fluorine
D. Fluorine
Which reaction will occur and equation is correct?
A. I₂ + 2KCl → 2KI + Cl₂
B. Cl₂ + 2KBr → 2KCl + Br₂
C. I₂ + 2KBr → 2KI + Br₂
D. Br₂ + 2KCl → 2KBr + Cl₂
B . Cl₂ + 2KBr → 2KCl + Br₂
Which silver halide forms a cream precipitate with AgNO₃?
A. AgCl
B. AgBr
C. AgI
D. AgF
B . AgBr
Nitrogen gas is unreactive at room temperature mainly because:
A. It is non-polar
B. It has a low boiling point
C. It contains a strong triple bond
D. It has a small atomic radius
C. strong triple bond
Which statement best explains why nitrogen monoxide (NO) is formed inside car engines?
A. Nitrogen reacts with oxygen at low temperature in the atmosphere
B. Nitrogen and oxygen react due to ultraviolet radiation
C. High temperature in the engine provides enough energy to break the N≡N bond
D. Nitrogen is highly reactive under normal conditions
C. High temperature in the engine provides enough energy to break the N≡N bond
Down Group 17, the boiling points of the halogens __________ because __________ forces increase due to larger atomic size.
Down Group 17, boiling points increase because London forces increase due to larger atomic size.
Reactivity of halogens __________ down Group 17 because the ability to __________ an electron decreases.
Reactivity of halogens decreases down the group because the ability to gain an electron decreases.
Silver chloride dissolves in __________ ammonia because __________ ions are formed.
dilute
complex ions
Ammonia acts as a __________ because it accepts a __________ from an acid.
✔base
✔ proton (H⁺)
Write the equation for the oxidation of NO to NO₂ in the atmosphere.
2NO(g) + O₂(g) → 2NO₂(g)
State the physical state and colour at room temperature of:
a) Bromine
b) Iodine
a) Bromine – reddish-brown liquid
b) Iodine – grey solid
Write the balanced equation for the reaction of chlorine with hydrogen, including state symbols and reaction condition.
H₂(g) + Cl₂(g) → 2HCl(g)
Condition: UV light / sunlight
A precipitate forms with AgNO₃. It does not dissolve in dilute NH₃, but does dissolve in concentrated NH₃.
Identify the halide ion.
Bromide (Br⁻)
State the shape and bond angle of the ammonium ion, NH₄⁺
✔ Tetrahedral
✔ 109.5°
Acid rain containing nitric acid forms when __________ dissolves in rainwater and reacts with __________.
NO₂
water (H₂O)
Which hydrogen halide is least thermally stable?
A. HF
B. HCl
C. HBr
D. HI
D – HI
When solid NaCl reacts with concentrated H₂SO₄, the reaction is best described as:
A. Redox reaction
B. Neutralisation
C. Acid–base reaction only
D. Disproportionation
C . Acid–base reaction only
Write a balanced chemical equation (with state symbols) for the reaction between aqueous potassium iodide and aqueous silver nitrate.
KI(aq) + AgNO₃(aq) → AgI(s) + KNO₃(aq)
Write a balanced chemical equation, including state symbols, for the reaction between solid ammonium sulfate and solid sodium hydroxide, when the mixture is heated.
(NH₄)₂SO₄(s) + 2NaOH(s) → 2NH₃(g) + 2H₂O(l) + Na₂SO₄(s)
Explain why nitrogen oxides are classified as primary pollutants, but PAN is a secondary pollutant.
Nitrogen oxides are released directly → primary pollutants
PAN forms in sunlight from NOx + hydrocarbons → secondary pollutant
Explain why the thermal stability of hydrogen halides decreases down the group, referring to bond length and bond energy.
Bond length increases down the group
Bond energy decreases
Weaker H–X bond breaks more easily → lower thermal stability
Solid NaBr reacts with concentrated sulfuric acid producing reddish-brown fumes.
a) Name the gas observed
b) State whether H₂SO₄ is oxidised or reduced
a) Bromine (Br₂)
b) Sulfuric acid is reduced (to SO₂)
A student adds silver nitrate solution to an unknown halide solution and observes a pale yellow precipitate.
When both dilute and concentrated ammonia are added, the precipitate does not dissolve.
a) Identify the halide ion present
b) Name the silver halide formed
a) Iodide ion (I⁻)
b) Silver iodide (AgI)
Explain why the reaction between NH₄Cl and NaOH is classified as an acid–base reaction.
NH₄⁺ donates a proton
OH⁻ accepts a proton
Proton transfer → acid–base reaction
State two environmental or health effects of photochemical smog caused by nitrogen oxides.
✔ Lung and eye irritation
✔ Damage to plants
✔ Reduced visibility
✔ Acid rain formation