Match each sulfur-related compound or allotrope on the left with its correct physical char… — JAMB UTME

Match each sulfur-related compound or allotrope on the left with its correct physical characteristic, qualitative test, or stability range on the right.

Rhombic sulfur ( $\alpha$ -sulfur)Octahedral crystalline allotrope stable at room temperature and up to $96^\circ\text{C}$
Hydrogen sulfide ( $H_2S$ )Gas with a rotten-egg odor that turns moist lead(II) ethanoate paper shiny black
Sulfur(IV) oxide ( $SO_2$ )Gas with a choking odor that turns acidified potassium dichromate(VI) solution from orange to green
Monoclinic sulfur ( $\beta$ -sulfur)Needle-shaped crystalline allotrope stable between $96^\circ\text{C}$ and $119^\circ\text{C}$

Answer

Rhombic sulfur matches the octahedral allotrope stable up to 96°C; Hydrogen sulfide matches the rotten-egg smelling gas turning lead(II) ethanoate paper black; Sulfur(IV) oxide matches the choking gas turning acidified potassium dichromate(VI) green; Monoclinic sulfur matches the needle-shaped allotrope stable between 96°C and 119°C.

Rhombic sulfur (

\alpha

-sulfur) is octahedral and stable below

96^\circ\text{C}

. Monoclinic sulfur (

\beta

-sulfur) is needle-shaped and stable between

96^\circ\text{C}

and

119^\circ\text{C}

. Hydrogen sulfide (

H_2S

) is a gas with a rotten-egg odor that reacts with

Pb^{2+}

to form black insoluble

PbS

. Sulfur(IV) oxide (

SO_2

) has a pungent choking smell and reduces orange dichromate(VI) solutions to green

Cr^{3+}

ions.

Step-by-Step Solution

Analyze the crystal structures and thermal stability range of sulfur allotropes.

Rhombic sulfur is octahedral and stable below 96°C. Monoclinic sulfur is needle-shaped and stable between 96°C and 119°C.

96°C is the transition temperature at which the two crystalline allotropes exist in equilibrium.

Identify the qualitative gas tests and chemical properties of

H_2S

and

SO_2

H_2S

forms black

PbS

precipitate with lead(II) ethanoate paper.

SO_2

reduces orange dichromate(VI) to green

Cr^{3+}

ions.

Both gases are reducing agents, but

H_2S

forms insoluble sulfides while

SO_2

undergoes specific color-change redox reactions with dichromate ions.

Key Concept

Physical and chemical properties of sulfur allotropes, hydrogen sulfide, and sulfur(IV) oxide

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