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In Chemistry / High School | 2025-07-08

Which reaction is endothermic?

A. [tex]HCl + NaOH \rightarrow NaCl + H _2 O +58 kJ[/tex]
B. [tex]6 CO _2+12 H _2 O +[/tex] energy [tex] \rightarrow C _6 H _{12} O _6+6 O _2+6 H _2 O[/tex]
C. [tex]2 Na + Cl _2 \rightarrow 2 NaCl +[/tex] energy
D. [tex]2 C _2 H _6+7 O _2 \rightarrow 4 CO _2+6 H _2 O +2,502 kJ[/tex]

Asked by mkolenda26

Answer (1)

Endothermic reactions absorb energy.
Examine each reaction to see if energy is absorbed or released.
6 C O 2 ​ + 12 H 2 ​ O + energy → C 6 ​ H 12 ​ O 6 ​ + 6 O 2 ​ + 6 H 2 ​ O is the only reaction that absorbs energy.
Therefore, the endothermic reaction is: 6 C O 2 ​ + 12 H 2 ​ O + energy → C 6 ​ H 12 ​ O 6 ​ + 6 O 2 ​ + 6 H 2 ​ O .

Explanation

Identifying Endothermic Reactions We need to identify the endothermic reaction from the given options. An endothermic reaction is one that absorbs energy from its surroundings. This is usually indicated by the presence of 'energy' on the reactant side of the equation or a negative enthalpy change.

Analyzing Each Reaction Let's examine each reaction:

H Cl + N a O H → N a Cl + H 2 ​ O + 58 k J : This reaction releases energy (58 kJ) on the product side, so it is exothermic.

6 C O 2 ​ + 12 H 2 ​ O + e n er g y → C 6 ​ H 12 ​ O 6 ​ + 6 O 2 ​ + 6 H 2 ​ O : This reaction absorbs energy on the reactant side, so it is endothermic.

2 N a + C l 2 ​ → 2 N a Cl + e n er g y : This reaction releases energy on the product side, so it is exothermic.

2 C 2 ​ H 6 ​ + 7 O 2 ​ → 4 C O 2 ​ + 6 H 2 ​ O + 2502 k J : This reaction releases energy (2502 kJ) on the product side, so it is exothermic.

Conclusion The second reaction, 6 C O 2 ​ + 12 H 2 ​ O + e n er g y → C 6 ​ H 12 ​ O 6 ​ + 6 O 2 ​ + 6 H 2 ​ O , is the only one that absorbs energy. Therefore, it is the endothermic reaction.


Examples
Endothermic reactions are crucial in many real-world applications. For example, the process of photosynthesis in plants, where carbon dioxide and water are converted into glucose and oxygen using sunlight (energy), is an endothermic reaction. Similarly, melting ice requires energy input from the surroundings, making it an endothermic process. Understanding endothermic reactions helps us analyze and optimize various chemical and physical processes in industries and everyday life.

Answered by GinnyAnswer | 2025-07-08