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Chapter 6: Problem 23

Explain the meaning of this thermochemical equation: $$ \begin{aligned} 4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}(g) &+6 \mathrm{H}_{2} \mathrm{O}(g) \\ \Delta H=&-904 \mathrm{~kJ} / \mathrm{mol} \end{aligned} $$

Short Answer

Expert verified
The given thermochemical equation represents an exothermic reaction where 4 moles of NH_3 reacts with 5 moles of O_2, producing 4 moles of NO and 6 moles of H2O, and in the process releasing 904 kJ of heat energy per mole of O_2 reacted.

Step by step solution

01

Break Down the Reaction Components

The reaction given is 4NH_3(g) + 5O_2(g) → 4NO(g) + 6H_2O(g). This implies that 4 moles of gaseous ammonia (NH_3) reacts with 5 moles of gaseous oxygen O_2 to yield 4 moles of nitrogen monoxide (NO) and six moles of water (H_2O) in a gaseous state.
02

Understand Exothermic Reaction

The sign before ∆H is negative, which means this is an exothermic reaction. Exothermic reactions are characterized by a net release of energy, which means they give off heat.
03

Interpret the Coefficients

The coefficients (the numbers before the chemical formulas) indicate the stoichiometry of the reaction. It represents the number of moles required or produced. Thus, 4 moles of NH_3 are needed to react with 5 moles of O_2 to produce 4 moles of NO and 6 moles of H_2O according to this equation.
04

Understand Heat of Reaction

The ∆H = -904 kJ/mol shows the heat of the reaction, which means that every mole of O_2 reacts with 4/5 mole of NH_3 producing -904 kJ of heat energy. Thus, the reaction is exothermic and releases 904 kJ of energy for every mole of O_2 reacted.

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Most popular questions from this chapter

In writing thermochemical equations, why is it important to indicate the physical state (that is, gaseous, liquid, solid, or aqueous) of each substance?

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A quantity of 0.020 mole of a gas initially at \(0.050 \mathrm{~L}\) and \(20^{\circ} \mathrm{C}\) undergoes a constant-temperature expansion until its volume is \(0.50 \mathrm{~L}\). Calculate the work done (in joules) by the gas if it expands (a) against a vacuum and (b) against a constant pressure of 0.20 atm. (c) If the gas in (b) is allowed to expand unchecked until its pressure is equal to the external pressure, what would its final volume be before it stopped expanding, and what would be the work done?
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