Strontium

Strontium, Sr²⁺

Most common oxidation state: +2

M.P. 770^o

B.P. 1380^o

Density 2.60 g/cm³

Characteristics: Active metal, very similar to barium and calcium.

Characteristic reactions of Sr²⁺:

Sulfate Ion:

Soluble sulfates, including sulfuric acid, precipitate white SrSO₄:

Sr²⁺(aq) + SO₄^2-(aq) <==> SrSO₄(s)

Chromate Ion:

Although chromate ion does not give a precipitate in neutral or acid solutions of Sr²⁺, yellow SrCrO₄ precipitates from slightly basic solution:

Sr²⁺(aq) + CrO₄^2-(aq) <==> SrCrO₄(s)

Strontium chromate dissolves readily in acids, even in acetic acid. It is only slightly soluble in alcohol or alcohol-water mixtures.

Oxalate Ion:

Oxalate ion precipitates white SrC₂O₄:

Sr²⁺(aq) + C₂O₄^2-(aq) <==> SrC₂O₄(s)

Strontium oxalate is insoluble in acetic acid, but soluble in mineral acids such as HCl:

SrC₂O₄(s) + 2H⁺(aq) <==> Sr²⁺(aq) + H₂C₂O₄(aq)

Ammonium Carbonate:

Ammonium carbonate precipitates white SrCO₃.

Sr²⁺(aq) + CO₃^2-(aq) <==> SrCO₃(s)

Aqueous ammonia should also be added to ensure complete precipitation. The aqueous ammonia assures that the concentration of carbonate ion will be high enough by preventing the hydrolysis of carbonate ion to form hydrogen carbonate ion:

NH₃(aq) + H₂O(l) <==> NH₄⁺(aq) + OH^-(aq)

CO₃^2-(aq) + H₂O(l) <==> HCO₃^-(aq) + OH^-(aq)

Strontium carbonate is soluble in acid, including dilute acetic acid, in strong bases, and in aqueous ammonia.

No Reaction:

Cl^-, NH₃(aq), OH^-

Go to cation menu