Heat of Reaction of Alkali metal with water.
Heat of Reaction of Alkali metal with water.
(OP)
Please, can someone help me out with the actual values of the Heat of Reaction of Potassium + Water, and Calcium Hydride + Water?
Thanks in advance.
Thanks in advance.





RE: Heat of Reaction of Alkali metal with water.
Data are from Perry’s, 7th ed., Table 2-220.
For potassium + water, the stoichiometric reaction (no excess water) is
K(s) + H2O(l) --> KOH(s) + ½ H2(g)
ΔHRxn, 25 C = -102.02 + 0 – 0 – (-68.32) = -33.7 kcal/mol
For potassium + water, with excess water (value is for final solution KOH in 400 H2O), the reaction is
K(s) + H2O(l) --> KOH(aq, 400H2O) + ½ H2(g)
ΔHRxn, 25 C = -114.96 + 0 – 0 – (-68.32) = -46.64 kcal/mol
For CaH2, the stoichiometric reaction (no excess water) is
CaH2(s) + 2 H2O(l) --> Ca(OH)2(s) + 2 H2(g)
ΔHRxn, 25 C = - 235.58 + 0 – (-46) – 2(-68.32) = -52.94 kcal/mol
For CaH2, the reaction with excess water is
CaH2(s) + 2 H2O(l) --> Ca(OH)2(aq, 800H2O) + 2 H2(g)
ΔHRxn, 25 C = - 239.2 + 0 – (-46) – 2(-68.32) = -56.56 kcal/mol
These reactions may be vigorous, and possibly explosive without excess water. Lots of heat (even more if the H2 ignites!). What is your application?
RE: Heat of Reaction of Alkali metal with water.