Question

state the observation for the following , also give equation for same .

1 ) copper is exposed to air . continued written 2,3,4,5 questions in the above image ​

Answer 1

Answer:

The dissolution of CaO will produce free calcium and hydroxyls (OH-), thus generating a highly basic solution, and a precipitate, Ca(OH)2 or calcium hydroxide, the mineral portlandite (also known as slaked lime), which is relatively insoluble in water (a solubility of 1.73 g/L at 20C, according to the infallible Wikipedia). Thus the initial dissolution reaction looks like,

H2O + CaO → Ca(2+) + 2OH(-)

with subsequent precipitation of Ca(OH)2:

Ca(2+) + 2OH(-) = Ca(OH)2

If formation of portlandite (above reaction) is allowed to determine the pH of the final solution — and here I use a portlandite equilibrium constant (i.e., the reverse of the reaction immediately above) of 10^(-5.435) — I compute a high pH of 12.4 at 25 C.

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