Calcium

Chemical reactions

Reaction of calcium with acids


Calcium metal dissolves readily in dilute or concentrated hydrochloric acid forming Ca(II) ions and hydrogen gas, H2.

Ca(s) + 2 HCl(aq) Ca2+(aq) + 2 Cl−(aq) + H2(g)


Reaction of calcium with air


At room temperature, calcium reacts with oxygen, forming a thin layer of CaO, that protects the metal from further oxidation. Calcium can be ignited and will when burning react with both oxygen and nitrogen forming calcium oxide, CaO, and calcium nitride, Ca3N2.

2 Ca(s) + O2(g) 2 CaO(s)
3 Ca(s) + N2(g) Ca3N2(s)


Reaction of calcium with carbonate ions


Calcium ions are precipitated by carbonate ions in neutral to alkaline solutions [6]:

Ca2+(aq) + CO32−(aq) CaCO3(s) [white]


Reaction of calcium with halogens


Calcium reacts readily halogens forming the corresponding dihalides. The reactions with fluorine and chlorine are exothermic while the reactions with bromine and iodine are endothermic.

Ca(s) + F2(g) CaF2(s)
Ca(s) + Cl2(g) CaCl2(s) [6]
Ca(s) + Br2(g) CaBr2(s)
Ca(s) + I2(g) CaI2(s)


Reaction of calcium with hydrogen


Calcium reacts with hydrogen, forming calcium hydride [6].

Ca(s) + H2(g) CaH2(s)


Reaction of calcium with hydroxide


Calcium ions can be precipitated by strong bases provided the concentration of calcium is sufficient.

Ca2+(aq) + 2 OH−(aq) Ca(OH)2(s)


Reaction of calcium with oxalate


Calcium ions are precipitated by oxalate ions.

Ca2+(aq) + HC2O4−(aq) CaC2O4(s) [white] + H+(aq)

The oxalate can be dissolved by mineral acids but not acetic acid.


Reaction of calcium with phosphate


Calcium ions are precipitated by phosphate ions in alkaline solutions.

5 Ca2+(aq) + 3 PO43−(aq) + OH−(aq) Ca5(SO4)3OH(s) [white]


Reaction of calcium with sulfate


Calcium ions are precipitated by sulfate ions in neutral to alkaline solutions.

Ca2+(aq) + SO42−(aq) CaSO4(s) [white]


Reaction of calcium with sulfide


Calcium ions can not be precipitated by sulfide.


Reaction of calcium with water


Calcium reacts slowly with water, forming calcium hydroxide and hydrogen.

Ca(s) + 2 H2O(l) Ca(OH)2(aq) + H2(g)


Quantitative analysis


Method 3500-Ca C Inductively Coupled Plasma Method [1]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.

Method limit of detection in water = 0.10 mg/L
Method limit of detection in soil = 100.0 mg/kg