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Answer: Lime is a term that includes calcium oxide (CaO,
Chapter 6, Problem 137P(choose chapter or problem)
Lime is a term that includes calcium oxide (CaO, also called quicklime) and calcium hydroxide \(\mathrm{Ca}(\mathrm{OH})_{2}\), also called slaked lime]. It is used in the steel industry to remove acidic impurities, in air-pollution control to remove acidic oxides such as \(\mathrm{SO}_{2}\), and in water treatment. Quicklime is made industrially by heating limestone \(\left(\mathrm{CaCO}_{3}\right)\) above \(2000^{\circ} \mathrm{C}\):
\(\mathrm{CaCO}_{3}(s) \rightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(g)\)
\(\Delta H^{\circ}=177.8\ \mathrm{kJ} / \mathrm{mol}\)
Slaked lime is produced by treating quicklime with water:
\(\mathrm{CaO}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})\)
\(\Delta H^{\circ}=-65.2\ \mathrm{kJ} / \mathrm{mol}\)
The exothermic reaction of quicklime with water and the rather small specific heats of both quicklime \(0.946\ \mathrm{J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\) and slaked lime \(\left(1.20\ \mathrm{J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\right)\) make it hazardous to store and transport lime in vessels made of wood. Wooden sailing ships carrying lime would occasionally catch fire when water leaked into the hold. (a) If a 500-g sample of water reacts with an equimolar amount of CaO (both at an initial temperature of \(25^{\circ} \mathrm{C}\)), what is the final temperature of the product, \(\mathrm{Ca}(\mathrm{OH})_{2}\)? Assume that the product absorbs all of the heat released in the reaction. (b) Given that the standard enthalpies of formation of CaO and \(\mathrm{H}_{2} \mathrm{O}\) are -635.6 kJ/mol and -285.8 kJ/mol, respectively, calculate the standard enthalpy of formation of \(\mathrm{Ca}(\mathrm{OH})_{2}\).
Questions & Answers
QUESTION:
Lime is a term that includes calcium oxide (CaO, also called quicklime) and calcium hydroxide \(\mathrm{Ca}(\mathrm{OH})_{2}\), also called slaked lime]. It is used in the steel industry to remove acidic impurities, in air-pollution control to remove acidic oxides such as \(\mathrm{SO}_{2}\), and in water treatment. Quicklime is made industrially by heating limestone \(\left(\mathrm{CaCO}_{3}\right)\) above \(2000^{\circ} \mathrm{C}\):
\(\mathrm{CaCO}_{3}(s) \rightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(g)\)
\(\Delta H^{\circ}=177.8\ \mathrm{kJ} / \mathrm{mol}\)
Slaked lime is produced by treating quicklime with water:
\(\mathrm{CaO}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})\)
\(\Delta H^{\circ}=-65.2\ \mathrm{kJ} / \mathrm{mol}\)
The exothermic reaction of quicklime with water and the rather small specific heats of both quicklime \(0.946\ \mathrm{J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\) and slaked lime \(\left(1.20\ \mathrm{J} / \mathrm{g} \cdot{ }^{\circ} \mathrm{C}\right)\) make it hazardous to store and transport lime in vessels made of wood. Wooden sailing ships carrying lime would occasionally catch fire when water leaked into the hold. (a) If a 500-g sample of water reacts with an equimolar amount of CaO (both at an initial temperature of \(25^{\circ} \mathrm{C}\)), what is the final temperature of the product, \(\mathrm{Ca}(\mathrm{OH})_{2}\)? Assume that the product absorbs all of the heat released in the reaction. (b) Given that the standard enthalpies of formation of CaO and \(\mathrm{H}_{2} \mathrm{O}\) are -635.6 kJ/mol and -285.8 kJ/mol, respectively, calculate the standard enthalpy of formation of \(\mathrm{Ca}(\mathrm{OH})_{2}\).
ANSWER:Step 1 of 4
(a)
The given reaction quicklime with water is written as follows:
