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Chapter 6: Problem 41

Are the following processes exothermic or endothermic? a. When solid \(\mathrm{KBr}\) is dissolved in water, the solution gets coldel 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 get 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

Process a: Dissolving solid KBr in water

When solid KBr is dissolved in water, the process makes the solution colder. Since the solution cools down, it indicates that the process absorbs heat from the surroundings. Therefore, the process is endothermic.
02

Process b: Burning natural gas (CH4) in a furnace

When natural gas (CH4) is burned in a furnace, it releases a large amount of heat. This heat is what makes the furnace hot and able to heat up a home or other space. Since the process releases heat, it is an exothermic process.
03

Process c: Adding concentrated H2SO4 to water

When concentrated H2SO4 is added to water, the solution gets very hot. This is because the process releases heat, which increases the temperature of the solution. Since heat is released, this process is exothermic.
04

Process d: Boiling water in a teakettle

When water is boiled in a teakettle, heat is absorbed from the heat source to increase the water's temperature. Once the water reaches its boiling point, it continues to absorb heat in order to undergo the phase change from a liquid to a gas (steam). Since heat is being absorbed, the process of boiling water is endothermic. In summary: a. Dissolving solid KBr in water - Endothermic b. Burning natural gas (CH4) in a furnace - Exothermic c. Adding concentrated H2SO4 to water - Exothermic d. Boiling water in a teakettle - Endothermic

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Most popular questions from this chapter

For the reaction \(\mathrm{HgO}(s) \rightarrow \mathrm{Hg}(l)+\frac{1}{2} \mathrm{O}_{2}(g), \Delta H=+90.7 \mathrm{~kJ}:\) a. What quantity of heat is required to produce \(1 \mathrm{~mol}\) of mercury by this reaction? b. What quantity of heat is required to produce \(1 \mathrm{~mol}\) of oxygen gas by this reaction? c. What quantity of heat would be released in the following reaction as written? $$ 2 \mathrm{Hg}(l)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{HgO}(s) $$

Consider \(5.5 \mathrm{~L}\) of a gas at a pressure of \(3.0 \mathrm{~atm}\) in a cylinder with a movable piston. The external pressure is changed so that the volume changes to \(10.5 \mathrm{~L}\). a. Calculate the work done, and indicate the correct sign. b. Use the preceding data but consider the process to occur in two steps. At the end of the first step, the volume is \(7.0 \mathrm{~L}\). The second step results in a final volume of \(10.5\) L. Calculate the work done, and indicate the correct sign. c. Calculate the work done if after the first step the volume is \(8.0 \mathrm{~L}\) and the second step leads to a volume of \(10.5 \mathrm{~L}\). Does the work differ from that in part b? Explain.

The standard enthalpy of formation of \(\mathrm{H}_{2} \mathrm{O}(l)\) at \(298 \mathrm{~K}\) is \(-285.8\) \(\mathrm{kJ} / \mathrm{mol} .\) Calculate the change in internal energy for the following process at \(298 \mathrm{~K}\) and 1 atm: $$ \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \quad \Delta E^{\circ}=? $$ (Hint: Using the ideal gas equation, derive an expression for work in terms of \(n, R\), and \(T\).)

Given the following data $$ \begin{array}{ll} \mathrm{NH}_{3}(g) \longrightarrow \frac{1}{2} \mathrm{~N}_{2}(g)+\frac{3}{2} \mathrm{H}_{2}(g) & \Delta H=46 \mathrm{~kJ} \\ 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(g) & \Delta H=-484 \mathrm{~kJ} \end{array} $$ calculate \(\Delta H\) for the reaction $$ 2 \mathrm{~N}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 3 \mathrm{O}_{2}(g)+4 \mathrm{NH}_{3}(g) $$ On the basis of the enthalpy change, is this a useful reaction for the synthesis of ammonia?

Consider the following changes: a. \(\mathrm{N}_{2}(g) \longrightarrow \mathrm{N}_{2}(l)\) b. \(\mathrm{CO}(g)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{H}_{2}(g)+\mathrm{CO}_{2}(g)\) c. \(\mathrm{Ca}_{3} \mathrm{P}_{2}(s)+6 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 3 \mathrm{Ca}(\mathrm{OH})_{2}(s)+2 \mathrm{PH}_{3}(g)\) d. \(2 \mathrm{CH}_{3} \mathrm{OH}(l)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(l)\) e. \(\mathrm{I}_{2}(s) \longrightarrow \mathrm{I}_{2}(g)\) At constant temperature and pressure, in which of these changes is work done by the system on the surroundings? By the surroundings on the system? In which of them is no work done?
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