Which of the following reactions shows that the formation of $CO _2$ releases $393.5 kJ / mol$?
A. $C (s)+ O _2(g) \rightarrow CO _2(g)+393.5 kJ$
B. $C ( s )+ O _2(g)+393.5 kJ \rightarrow CO _2(g)$
C. $C (s)+2 O (g)+393.5 kJ \rightarrow CO _2(g)$
D. $C (s)+ O (g) \rightarrow CO _2(g)+393.5 kJ$
Answer (2)
The formation of C O 2 releases 393.5 k J / m o l .
Option A correctly represents this exothermic reaction: C ( s ) + O 2 ( g ) i g h t ha r p oo n u pC O 2 ( g ) + 393.5 k J .
Options B, C, and D incorrectly represent the energy change or use incorrect chemical formulas.
The correct answer is A. A
Explanation
Understanding the Problem We need to identify the reaction that correctly represents the formation of C O 2 releasing 393.5 k J / m o l . In an exothermic reaction, energy is released as a product.
Analyzing Option A Option A: C ( s ) + O 2 ( g ) i g h t ha r p oo n u pC O 2 ( g ) + 393.5 k J . This reaction shows the formation of C O 2 and the release of 393.5 k J . This is the correct representation.
Analyzing Option B Option B: C ( s ) + O 2 ( g ) + 393.5 k J i g h t ha r p oo n u pC O 2 ( g ) . This reaction shows that 393.5 k J is added to the reactants, not released. This is incorrect.
Analyzing Option C Option C: C ( s ) + 2 O ( g ) + 393.5 k J i g h t ha r p oo n u pC O 2 ( g ) . This reaction is incorrect because it uses 2 moles of atomic oxygen instead of one mole of diatomic oxygen and also adds energy to the reactants.
Analyzing Option D Option D: C ( s ) + O ( g ) i g h t ha r p oo n u pC O 2 ( g ) + 393.5 k J . This reaction is incorrect because it uses atomic oxygen instead of diatomic oxygen.
Final Answer The correct reaction is A, which shows the formation of C O 2 and the release of 393.5 k J / m o l .
Examples
This concept is crucial in understanding energy changes in chemical reactions. For instance, when designing engines or power plants, engineers need to consider the heat released during combustion processes, like the formation of C O 2 , to optimize efficiency and prevent overheating. Knowing the energy released helps in managing the thermal output and designing appropriate cooling systems. This also applies to understanding climate change, where C O 2 emissions and their energy implications are significant.
The correct reaction showing that the formation of C O 2 releases 393.5 k J / m o l is Option A: C ( s ) + O 2 ( g ) → C O 2 ( g ) + 393.5 k J . This indicates that energy is released during the formation of carbon dioxide. Options B, C, and D incorrectly represent the reaction and energy changes.
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