A student needs to prepare a pure, dry sample of barium tetraoxosulfate(VI), BaSO_4, in th… — JAMB UTME

A student needs to prepare a pure, dry sample of barium tetraoxosulfate(VI), $BaSO_4$ , in the laboratory. Which of the following methods provides the most suitable procedure for obtaining this salt?

Mixing aqueous barium nitrate with aqueous sodium tetraoxosulfate(VI), filtering the precipitate, washing it with distilled water, and drying itAnswer
B
Titrating aqueous barium hydroxide with dilute tetraoxosulfate(VI) acid, evaporating the resulting solution to dryness, and crystallizing
C
Reacting solid barium carbonate with dilute tetraoxosulfate(VI) acid, filtering off the unreacted solid, and evaporating the filtrate to dryness
D
Heating barium metal directly in a stream of sulfur dioxide gas and collecting the crystalline residue

Answer

Mixing aqueous barium nitrate with aqueous sodium tetraoxosulfate(VI), filtering the precipitate, washing it with distilled water, and drying it

Barium tetraoxosulfate(VI) (

BaSO_4

) is insoluble in water. The standard laboratory procedure for preparing insoluble salts is double decomposition (precipitation), where two aqueous solutions containing the constituent ions (in this case,

Ba(NO_3)_2(aq)

and

Na_2SO_4(aq)

) are mixed. The insoluble salt precipitates immediately, is collected by filtration, washed with distilled water to eliminate spectator ions, and dried.

Step-by-Step Solution

Determine the solubility of the target salt

Barium tetraoxosulfate(VI),

BaSO_4

, is insoluble in water according to general solubility rules.

The method of salt preparation depends primarily on whether the target salt is soluble or insoluble.

Select the appropriate laboratory synthesis technique

Double decomposition (precipitation) between two soluble compounds containing the required cations and anions (

Ba^{2+}

and

SO_4^{2-}

) is required.

Insoluble salts are best prepared by combining solutions of two soluble salts to precipitate the insoluble product.

Identify the separation and purification steps

Filter the solid precipitate from the mixture, wash the residue with distilled water to remove soluble byproduct ions (

Na^+

and

NO_3^-

), and dry the solid.

Washing and drying ensure that a pure, dry sample of the insoluble salt is obtained.

Key Concept

Laboratory Preparation of Insoluble Salts by Double Decomposition (Precipitation)

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