Question #da5d4

1 Answer
Ernest Z.
Oct 25, 2016

#Δ_"r"H = "+109 kJ"#.

Explanation:

In this case, the statement of the problem gives you the answer.

However, you could also have solved the problem by looking up the standard enthalpy of formation of each of the substances.

The formula for enthalpy of reaction is

#color(blue)(bar(ul(|color(white)(a/a)Δ_rH^° = sumΔ_fH_text(products)^° - sumΔ_fH_text(reactants)^°color(white)(a/a)|)))" "#

#color(white)(mmmmmmmmm)"Ca(OH)"_2"(s)" → "CaO(s)" + "H"_2"O(g)"#
#Δ_text(f)H^°"/kJ·mol"^"-1": color(white)(l)+986.09color(white)(mmmll)"-635.0"color(white)(mll)"-241.83"#

∴ # Δ_rH = "[1(-635.0) + 1(-241.83) - 1(986.09)] kJ" = "+109.3 kJ"#

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