Chapter 9 Inorganic Chemistry – Halogens

A comprehensive set of practice flashcards covering the properties, trends, and reactions of Group 7 elements (halogens) and their compounds.

What are the colors and physical states of fluorine, chlorine, bromine, and iodine at room temperature and pressure (RTP)?

$F_2$: Yellow gas; $Cl_2$: Green gas; $Br_2$: Red/brown liquid; $I_2$: Grey solid.

Why does the boiling point of halogens increase and volatility decrease as you move down the group?

The number of electrons and molecular size increase down the group, leading to stronger temporary dipoles and increased van der Waals (intermolecular) forces, which require more energy to overcome.

Describe the trend in bond strength of the halogen molecules ($X_2$) as you move down the group.

Covalent bonds get weaker because atomic radius and shielding increase, moving the bonding pair further from the nucleus and weakening the attraction.

What is the trend in oxidizing strength among the halogens?

Oxidizing strength decreases down the group: $F_2 > Cl_2 > Br_2 > I_2$.

Why do halogens become less reactive as oxidizing agents down the group?

Increased shielding and a larger atomic radius offset the increased nuclear charge, resulting in a weaker attraction between the nucleus and an incoming electron.

What is a displacement reaction in the context of halogens?

A reaction where a more reactive halogen displaces a less reactive halogen from its halide solution (e.g., $Cl_2 (aq) + 2NaBr (aq) \rightarrow Br_2 (aq) + 2NaCl (aq)$).

In the reaction $Cl_2 + 2KBr \rightarrow 2KCl + Br_2$, identify what is oxidized and what is reduced.

Chlorine is reduced (gains electrons to become $Cl^-$) and bromide ions are oxidized (lose electrons to become $Br_2$).

How does the reactivity of halogens with hydrogen change down the group?

Reactivity decreases: Fluorine reacts explosively; Chlorine explodes in light; Bromine reacts slowly on heating; Iodine only partially reacts in an equilibrium state.

What is the trend for the thermal stability of hydrogen halides ($HX$)?

Thermal stability decreases down the group ($HF > HCl > HBr > HI$) because the $H-X$ bond length increases and bond strength decreases.

How does the reducing power of halide ions change down the group?

Reducing power increases down the group because increased shielding and atomic radius make it easier for the outer electrons to be lost.

What observations are made when silver nitrate ($AgNO_3$) is added to solutions of chloride, bromide, and iodide ions?

Chloride: white precipitate ($AgCl$); Bromide: cream precipitate ($AgBr$); Iodide: yellow precipitate ($AgI$).

Describe the solubility of silver halide precipitates in ammonia ($NH_3$).

$AgCl$ is soluble in dilute ammonia; $AgBr$ is insoluble in dilute but soluble in concentrated ammonia; $AgI$ is insoluble in both.

What are the products when concentrated sulfuric acid ($H_2SO_4$) reacts with solid sodium chloride ($NaCl$)?

$HCl$ (misty fumes) and $NaHSO_4$.

What are the additional products when concentrated $H_2SO_4$ reacts with $NaBr$ compared to $NaCl$?

$Br_2$ (red-brown gas) and $SO_2$ (choking gas) are produced because bromide is a stronger reducing agent.

What observations are unique to the reaction of concentrated $H_2SO_4$ with sodium iodide ($NaI$)?

Purple vapor ($I_2$), a yellow solid ($S$), and a bad egg smell ($H_2S$).

Define a disproportionation reaction.

A reaction in which the same element is both oxidized and reduced simultaneously.

What is the chemical equation for the reaction of chlorine with cold, aqueous sodium hydroxide ($NaOH$)?

$$2NaOH(aq) + Cl_2(g) \rightarrow NaCl(aq) + NaOCl(aq) + H_2O(l)$$

What is the product formed when chlorine reacts with hot, concentrated sodium hydroxide ($NaOH$)?

Sodium chlorate (V), $NaClO_3$, along with $NaCl$ and $H_2O$.

Why is chlorine added to water supplies?

It is toxic to bacteria, prevents reinfection, stops algae growth, and removes bad tastes, smells, and discoloration.

What is the main disinfecting agent produced when chlorine reacts with water?

Hypochlorous acid ($HOCl$).