Sodium arsenate

Sodium arsenate
Sodium arsenate
Are common
Systematic ; name	Sodium arsenate
Traditional names	Arsenic (ortho) sodium
Chem. formula	Na 3 AsO 4
Physical properties
Molar mass	207.89 g / mol
Density	2.835 g / cm³
Thermal properties
T. melt.	hydr. 86.3 ° C
Chemical properties
Solubility in water	19.1 15.5 ; 23.4 30 g / 100 ml
Classification
Reg. CAS number
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Reg. EINECS number
Smiles
Inchi
RTECS
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Toxicity	poisonous
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Sodium arsenate is an inorganic compound, a salt of an alkali metal of sodium and arsenic acid with the formula Na ₃ AsO ₄ , colorless crystals soluble in water form a crystalline hydrate ; poisonous.

Content

Getting

Dissolution of arsenic in sodium hydroxide solution in the presence of oxidizing agents:

{\mathsf {2As+6NaOH+5NaClO\ {\xrightarrow {}}\ 2Na_{3}AsO_{4}+5NaCl+3H_{2}O}}

{\ displaystyle {\ mathsf {2As + 6NaOH + 5NaClO \ {\ xrightarrow {}} \ 2Na_ {3} AsO_ {4} + 5NaCl + 3H_ {2} O}}}

Arsenic trioxide fusion with alkali and sodium nitrate :

{\mathsf {As_{2}O_{3}+6NaOH+2NaNO_{3}\ {\xrightarrow {400-500^{o}C}}\ 2Na_{3}AsO_{4}+2NaNO_{2}+3H_{2}O}}

{\ displaystyle {\ mathsf {As_ {2} O_ {3} + 6NaOH + 2NaNO_ {3} \ {\ xrightarrow {400-500 ^ {o} C}} \ 2Na_ {3} AsO_ {4} + 2NaNO_ {2 } + 3H_ {2} O}}}

Dissolution of arsenic pentoxide in concentrated alkali:

{\mathsf {As_{2}O_{5}+6NaOH\ {\xrightarrow {}}\ 2Na_{3}AsO_{4}+3H_{2}O}}

{\ displaystyle {\ mathsf {As_ {2} O_ {5} + 6NaOH \ {\ xrightarrow {}} \ 2Na_ {3} AsO_ {4} + 3H_ {2} O}}}

Decomposition of sodium meta arsenite :

{\mathsf {5NaAsO_{2}\ {\xrightarrow {300-550^{o}C}}\ Na_{3}AsO_{4}+2NaAsO_{3}+2As}}

{\ displaystyle {\ mathsf {5NaAsO_ {2} \ {\ xrightarrow {300-550 ^ {o} C}} \ Na_ {3} AsO_ {4} + 2NaAsO_ {3} + 2As}}}

or its oxidation:

{\mathsf {NaAsO_{2}+NaClO+2NaOH\ {\xrightarrow {}}\ Na_{3}AsO_{4}+NaCl+H_{2}O}}

{\ displaystyle {\ mathsf {NaAsO_ {2} + NaClO + 2NaOH \ {\ xrightarrow {}} \ Na_ {3} AsO_ {4} + NaCl + H_ {2} O}}}

Physical Properties

Sodium arsenate forms colorless crystals.

It is well soluble in water with partial hydrolysis by anion .

It forms crystalline hydrate Na ₃ AsO ₄ • 12H ₂ O, which melts in its own crystallization water at 86.3 ° С.

Chemical Properties

When heated, crystalline hydrate loses water:

{\mathsf {Na_{3}AsO_{4}\cdot 12H_{2}O\ {\xrightarrow {150^{o}C}}\ Na_{3}AsO_{4}+12H_{2}O}}

{\ displaystyle {\ mathsf {Na_ {3} AsO_ {4} \ cdot 12H_ {2} O \ {\ xrightarrow {150 ^ {o} C}} \ Na_ {3} AsO_ {4} + 12H_ {2} O }}}

In aqueous solutions it absorbs carbon dioxide:

{\mathsf {Na_{3}AsO_{4}+CO_{2}+H_{2}O\ {\xrightarrow {}}\ Na_{2}HAsO_{4}+NaHCO_{3}}}

{\ displaystyle {\ mathsf {Na_ {3} AsO_ {4} + CO_ {2} + H_ {2} O \ {\ xrightarrow {}} \ Na_ {2} HAsO_ {4} + NaHCO_ {3}}}}

With arsenic acid in the cold forms an acid salt crystalline hydrate:

{\mathsf {Na_{3}AsO_{4}+2H_{3}AsO_{4}+3H_{2}O\ {\xrightarrow {}}\ 3(NaH_{2}AsO_{4}\cdot H_{2}O)}}

{\ displaystyle {\ mathsf {Na_ {3} AsO_ {4} + 2H_ {3} AsO_ {4} + 3H_ {2} O \ {\ xrightarrow {}} \ 3 (NaH_ {2} AsO_ {4} \ cdot H_ {2} O)}}}

It enters into metabolic reactions:

{\mathsf {Na_{3}AsO_{4}+3AgNO_{3}\ {\xrightarrow {}}\ Ag_{3}AsO_{4}\downarrow +3NaNO_{3}}}

{\ displaystyle {\ mathsf {Na_ {3} AsO_ {4} + 3AgNO_ {3} \ {\ xrightarrow {}} \ Ag_ {3} AsO_ {4} \ downarrow + 3NaNO_ {3}}}}

It is a weak oxidizing agent:

{\mathsf {2Na_{3}AsO_{4}+4HI+3H_{2}SO_{4}\ {\xrightarrow {}}\ As_{2}O_{3}\downarrow +2I_{2}+3Na_{2}SO_{4}+5H_{2}O}}

{\ displaystyle {\ mathsf {2Na_ {3} AsO_ {4} + 4HI + 3H_ {2} SO_ {4} \ {\ xrightarrow {}} \ As_ {2} O_ {3} \ downarrow + 2I_ {2} + 3Na_ {2} SO_ {4} + 5H_ {2} O}}}

Literature

Chemistry Handbook / Editorial: Nikolsky B.P. et al. - 3rd ed., rev. - L .: Chemistry, 1971. - T. 2. - 1168 p.
Lidin R.A. and other Chemical properties of inorganic substances: Textbook. manual for universities. - 3rd ed., Rev. - M .: Chemistry, 2000 .-- 480 p. - ISBN 5-7245-1163-0 .