Question

Which reaction is endothermic?
HCl + NaOH Right arrow. NaCl + H2O + 58 kJ
6CO2 + 12H2O + energy Right arrow. C6H12O6 + 6O2 + 6H2O
2Na + Cl2 Right arrow. 2NaCl + energy
2C2H6 + 7O2 Right arrow. 4CO2 + 6H2O + 2,502 kJ

Answer 1

An endothermic reaction is one that absorbs energy from its surroundings, indicated by a positive change in enthalpy.

Let's analyze each of the reactions given:

1. **HCl + NaOH → NaCl + H2O + 58 kJ**
- This reaction releases energy (58 kJ), making it exothermic.

2. **6CO2 + 12H2O + energy → C6H12O6 + 6O2 + 6H2O**
- This reaction absorbs energy (indicated by "energy" as a reactant), making it endothermic.

3. **2Na + Cl2 → 2NaCl + energy**
- This reaction also releases energy, making it exothermic.

4. **2C2H6 + 7O2 → 4CO2 + 6H2O + 2,502 kJ**
- This reaction releases a substantial amount of energy, making it exothermic.

Based on the analysis, the reaction that is endothermic is:

**6CO2 + 12H2O + energy → C6H12O6 + 6O2 + 6H2O**