Endothermic Reaction Chemistry Example 3

Follow the full solution, then compare it with the other examples linked below.

Example 3

medium
Photosynthesis absorbs 2803 kJ per mole of glucose. Is it endothermic or exothermic? What is the sign of ฮ”H\Delta H?

Solution

  1. 1
    The problem states that photosynthesis **absorbs** 2803 kJ of energy per mole of glucose produced.
  2. 2
    A reaction that absorbs energy from its surroundings is classified as **endothermic**.
  3. 3
    For endothermic reactions, the enthalpy change is positive: ฮ”H=+2803โ€‰kJ/mol>0\Delta H = +2803\,\text{kJ/mol} > 0. The overall reaction is: 6CO2+6H2Oโ†’lightC6H12O6+6O2ฮ”H=+2803โ€‰kJ6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{light}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \quad \Delta H = +2803\,\text{kJ}

Answer

Photosynthesis is endothermic. ฮ”H=+2803โ€‰kJ/mol\Delta H = +2803\,\text{kJ/mol} (positive).
Photosynthesis requires a continuous input of light energy to convert low-energy molecules (CO2\text{CO}_2 and H2O\text{H}_2\text{O}) into high-energy glucose. Because the products store more energy than the reactants, ฮ”H>0\Delta H > 0, confirming it is endothermic.

About Endothermic Reaction

A chemical reaction that absorbs energy (usually as heat) from the surroundings, resulting in a decrease in surrounding temperature and a positive enthalpy change (ฮ”H>0\Delta H > 0).

Learn more about Endothermic Reaction โ†’

More Endothermic Reaction Examples

Example 1 easy

Photosynthesis absorbs energy: [formula]. Why is this endothermic?

Example 2 medium

An instant cold pack contains ammonium nitrate and water. When the inner bag is broken, the temperat

Example 4 easy

Cooking an egg requires continuous heat input. Is this an endothermic or exothermic process?

Example 5 easy

An instant cold pack becomes cold when activated. Is the process inside the pack exothermic or endot

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