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What can you conclude about these two reactions based on the chemical equations?



Reaction A: $6 CO _2(g)+6 H _2 O (\ell)+$ sunlight $\rightarrow C _6 H _{12} O _6(aq)+6 O _2(g)$

Reaction B: $2 H _2(g)+ O _2(g) \rightarrow 2 H _2 O (g)+$ energy


AReactions A and B are both exothermic.
BReaction A is endothermic, and reaction B is exothermic.
CReactions A and B are both endothermic.
DReaction A is exothermic, and reaction B is endothermic.

Verified Answer :

  • Reaction A involves absorbing "sunlight" as a reactant, making it an endothermic process.
  • Reaction B produces "energy" as an output, making it an exothermic process.
  • Therefore, the correct conclusion is that Reaction A is endothermic and Reaction B is exothermic.
  • Final answer: \(\boxed{\text{Reaction A is endothermic, and reaction B is exothermic}}\).

Explanation

  1. Analysis of Reaction Types

To determine the classification of the given chemical reactions, we must examine the role of energy within each equation.

Reaction A is given by:
\[6 CO_2(g) + 6 H_2O(\ell) + \text{sunlight} \rightarrow C_6H_{12}O_6(aq) + 6 O_2(g)\]
In this equation, "sunlight" acts as a reactant, meaning that energy must be supplied (absorbed) from the environment for the reaction to proceed. Reactions that absorb energy are classified as endothermic.

Reaction B is given by:
\[2 H_2(g) + O_2(g) \rightarrow 2 H_2O(g) + \text{energy}\]
In this equation, "energy" appears as a product, indicating that the chemical process releases energy into the surroundings. Reactions that release energy are classified as exothermic.

  1. Conclusion of Results

Based on our analysis:

  • Reaction A absorbs energy ("sunlight") to proceed, so it is endothermic.
  • Reaction B releases energy as a product, so it is exothermic.

Comparing these conclusions to the given options:

  • Reactions A and B are both exothermic (Incorrect).
  • Reaction A is endothermic, and reaction B is exothermic (Correct).
  • Reactions A and B are both endothermic (Incorrect).
  • Reaction A is exothermic, and reaction B is endothermic (Incorrect).

Thus, the correct conclusion is that Reaction A is endothermic, and reaction B is exothermic.

Examples

Photosynthesis, which is modeled by Reaction A, is a vital endothermic process where plants convert solar energy into chemical energy to create food. Conversely, the combustion of hydrogen (Reaction B) is an exothermic process, often used in rocket engines to generate powerful bursts of energy for liftoff. Understanding these energy transformations helps scientists design efficient energy storage systems and study the energetics of life-sustaining processes.

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