What is the pH of calcium oxide

Calcium oxideCaO
White dust
molar mass 56.077 g / mol

AGW1 mg / m3E (TRGS 900)
Melting point + 2613 ° C
density 3.34 g / cm3   
Water solubility (alkaline)   
converts to calcium hydroxide
GHS 05
GHS 07
Hazard classes + category 
Serious eye damage 1
Irritant effect on the skin 2
Specific target organ toxicity, one time. 3
HP rates (see also note) 
H 315, 318, 335
P 261, 280.1-3, 305 + 351 + 338
G 4
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CAS 1305-78-8Calcium oxideCalcium oxide
Calcium oxide is traded in impure form under the name "quicklime" or "burnt lime". It reacts with water to form calcium hydroxide with strong heat development. Every time water is added to calcium oxide, lime water is produced, which has an alkaline reaction.
CaO + H2O Ca (OH)2       ΔHR. = −65 kJ / mol
Ca (OH)2 + H2O Approx2+ + 2 OH + H2O
Because of this reaction, which of course also takes place immediately with body fluids, calcium oxide is classified as a hazardous substance in the same way as calcium hydroxide. A violent reaction can also be observed with the addition of acids, glycerine and a sugar solution. Calcium oxide is not soluble in ethanol. It attracts water and carbon dioxide from the air, so that it gradually breaks down into calcium carbonate.

Calcium oxide reacts with water while generating heat.
Quicklime is made by heating calcium carbonate to over 1000 ° C. In the laboratory, it can also be obtained by burning calcium:
2 Ca + O2  2 CaO
The largest proportion of calcium oxide is required for the production of mortar. It is also used as a raw material for the industrial production of artificial sand-lime bricks. Calcium oxide is approved as a food additive E 526 and acts there as an acidity regulator. In the laboratory it is suitable as a desiccant for substances and as an absorbent for carbon dioxide. Since calcium oxide reacts with water to form calcium hydroxide, it can be used for the preparation of lime water. The chemical industry needs it to produce other calcium compounds such as calcium carbide or chlorinated lime. It is used as a flotation aid in metal extraction. Calcium oxide is also needed in glass, paper, soda and sugar production.

Old lime kiln near Marchtal in the Allgäu