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Chapter 6: Problem 48

Are the following processes exothermic or endothermic? a. the combustion of gasoline in a car engine b. water condensing on a cold pipe c. \(\mathrm{CO}_{2}(s) \longrightarrow \mathrm{CO}_{2}(g)\) d. \(\mathrm{F}_{2}(g) \longrightarrow 2 \mathrm{F}(g)\)

Short Answer

Expert verified
a. The combustion of gasoline in a car engine is an exothermic process. b. Water condensing on a cold pipe is an exothermic process. c. \(CO_{2}(s) \longrightarrow CO_{2}(g)\) is an endothermic process. d. \(F_{2}(g) \longrightarrow 2 F(g)\) is an endothermic process.

Step by step solution

01

a. Combustion of gasoline in a car engine

Combustion is a chemical reaction that occurs between a fuel and an oxidant, producing heat and light in the form of a flame. In this process, the chemical potential energy stored within the gasoline is converted into thermal energy. Since heat is released during combustion, this process is exothermic.
02

b. Water condensing on a cold pipe

When water condenses, it changes from its gaseous state (water vapor) to its liquid state. This phase transition is accompanied by the release of energy in the form of heat. Therefore, the condensation of water on a cold pipe is an exothermic process.
03

c. CO2(s) → CO2(g)

The process described here is the sublimation of solid carbon dioxide (CO2) into gaseous carbon dioxide. During sublimation, energy is absorbed by the solid CO2 to break the intermolecular forces holding the solid structure together, resulting in a transition to the gaseous state. Thus, this process is endothermic because it requires an input of energy (heat) for the phase change to occur.
04

d. F2(g) → 2 F(g)

The given reaction represents the dissociation of a diatomic fluorine molecule (F2) into two separate fluorine atoms (F). Breaking the chemical bond between the two fluorine atoms requires an input of energy since chemical bonds store energy. Therefore, this process is endothermic.

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Most popular questions from this chapter

For the process $\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{O}(g)\( at 298 \)\mathrm{K}\( and \)1.0 \mathrm{atm},\( \)\Delta H$ is more positive than \(\Delta E\) by 2.5 \(\mathrm{kJ} / \mathrm{mol}\) . What does the 2.5 \(\mathrm{kJ} / \mathrm{mol}\) quantity represent?

The preparation of \(\mathrm{NO}_{2}(g)\) from \(\mathrm{N}_{2}(g)\) and \(\mathrm{O}_{2}(g)\) is an endothermic reaction: $$ \mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{NO}_{2}(g)(\text { unbalanced }) $$ The enthalpy change of reaction for the balanced equation (with lowest whole- number coefficients) is \(\Delta H=67.7 \mathrm{kJ}\) . If $2.50 \times 10^{2} \mathrm{mL} \mathrm{N}_{2}(g)\( at \)100 .^{\circ} \mathrm{C}$ and 3.50 atm and \(4.50 \times\) \(10^{2} \mathrm{mL} \mathrm{O}_{2}(g)\) at $100 .^{\circ} \mathrm{C}$ and 3.50 atm are mixed, what amount of heat is necessary to synthesize the maximum yield of \(\mathrm{NO}_{2}(g) ?\)

A serving size of six cookies contains 4 g of fat, 20 of carbohydrates, and 2 g of protein. If walking 1.0 mile consumes 170 kJ of energy, how many miles must you walk to burn off enough calories to eat six cookies? Assume the energy content of fats, carbohydrates, and proteins are 8 kcallg, 4 kcallg, and 4 kcallg, respectively.

Write reactions for which the enthalpy change will be a. \(\Delta H_{\mathrm{f}}^{\circ}\) for solid aluminum oxide. b. the standard enthalpy of combustion of liquid ethanol, $$ \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l) . $$ c. the standard enthalpy of neutralization of sodium hydroxide solution by hydrochloric acid. d. \(\Delta H_{\mathrm{f}}^{\circ}\) for gaseous vinyl chloride, $\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{Cl}(g)$ e. the enthalpy of combustion of liquid benzene, $\mathrm{C}_{6} \mathrm{H}_{6}(l)$ f. the enthalpy of solution of solid ammonium bromide.

What is incomplete combustion of fossil fuels? Why can this be a problem?
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