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Chapter 6: Problem 47

Are the following processes exothermic or endothermic? a. When solid \(\mathrm{KBr}\) is dissolved in water, the solution gets colder. b. Natural gas \(\left(\mathrm{CH}_{4}\right)\) is burned in a furnace. c. When concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is added to water, the solution gets very hot. d. Water is boiled in a teakettle.

Short Answer

Expert verified
a. Endothermic b. Exothermic c. Exothermic d. Endothermic

Step by step solution

01

a. Solid KBr is dissolved in water#{tag_content}#The solution gets colder when solid \(\mathrm{KBr}\) is dissolved in water. A process that causes the surrounding environment to become colder is likely absorbing heat, which indicates that this is an endothermic process.

b. Natural gas is burned in a furnace#{tag_content}#Burning natural gas, or \(\mathrm{CH}_{4}\), in a furnace is a combustion reaction. Combustion reactions involve combining a fuel source with oxygen and releasing energy in the form of heat and light. Since the reaction releases heat, it is an exothermic process.
02

c. Concentrated H2SO4 is added to water#{tag_content}#When concentrated sulfuric acid, \(\mathrm{H}_{2} \mathrm{SO}_{4}\), is added to water, the solution gets very hot. This indicates that heat is being released during this process. Since heat is being released, it is an exothermic process.

d. Water is boiled in a teakettle#{tag_content}#Boiling water involves adding energy in the form of heat to increase the temperature of the water until it reaches its boiling point and turns into steam. Since the process requires an input of energy in the form of heat, it is an endothermic process.

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Most popular questions from this chapter

Given the following data: $$ \begin{array}{ll}{\mathrm{NO}_{2}(g) \longrightarrow \mathrm{NO}(g)+\mathrm{O}(g)} & {\Delta H=233 \mathrm{kJ}} \\ {2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g)} & {\Delta H=-427 \mathrm{kJ}}\end{array} $$ $$ \mathrm{NO}(g)+\mathrm{O}_{3}(g) \longrightarrow \mathrm{NO}_{2}(g)+\mathrm{O}_{2}(g) \quad \Delta H=-199 \mathrm{kJ} $$ Calculate the bond energy for the \(\mathrm{O}_{2}\) bond, that is, calculate \(\Delta H\) for: $$ \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{O}(g) \qquad \Delta H=? $$

The reaction $$ \mathrm{SO}_{3}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}(a q) $$ is the last step in the commercial production of sulfuric acid. The enthalpy change for this reaction is \(-227 \mathrm{kJ} .\) In designing a sulfuric acid plant, is it necessary to provide for heating or cooling of the reaction mixture? Explain.

A piston performs work of \(210 . \mathrm{L} \cdot\) atm on the surroundings, while the cylinder in which it is placed expands from \(10 . \mathrm{L}\) to 25 \(\mathrm{L}\) . At the same time, 45 \(\mathrm{J}\) of heat is transferred from the surroundings to the system. Against what pressure was the piston working?

Consider a balloon filled with helium at the following conditions. $$ \begin{array}{l}{313 \mathrm{g} \mathrm{He}} \\ {1.00 \mathrm{atm}} \\ {1910 . \mathrm{L}} \\ {\text { Molar Heat Capacity }=20.8 \mathrm{J} / \mathrm{C} \cdot \mathrm{mol}}\end{array} $$ The temperature of this balloon is decreased by \(41.6^{\circ} \mathrm{C}\) as the volume decreases to \(1643 \mathrm{L},\) with the pressure remaining constant. Determine \(q, w,\) and $\Delta E(\text { in } \mathrm{kJ} \text { ) for the compression of }$ the balloon.

The combustion of 0.1584 g benzoic acid increases the temperature of a bomb calorimeter by \(2.54^{\circ} \mathrm{C}\) . Calculate the heat capacity of this calorimeter. (The energy released by combustion of benzoic acid is 26.42 \(\mathrm{kJ} / \mathrm{g} .\) ) A \(0.2130-\mathrm{g}\) sample of vanillin \(\left(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}_{3}\right)\) is then burned in the same calorimeter, and the temperature increases by $3.25^{\circ} \mathrm{C}$ . What is the energy of combustion per gram of vanillin? Per mole of vanillin?
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