Final answer:
Combustion and decomposition reactions are spontaneous (favorable). Photosynthesis and endothermic reactions are not spontaneous.
Step-by-step explanation:
In Chemistry, spontaneous reactions are those that favor the formation of products under the given conditions. Spontaneous reactions are usually exothermic, meaning that they release energy to the surroundings as heat. Examples of spontaneous reactions include combustion and decomposition reactions.
In the provided list of reactions, the ones that are spontaneous (favorable) are:
- Combustion
- Decomposition
Photosynthesis, on the other hand, is not spontaneous. It requires an input of energy to produce glucose and oxygen from carbon dioxide and water.
An endothermic reaction, by definition, is a non-spontaneous reaction as it requires an input of energy to proceed. So, the reaction labeled as 'Endothermic reaction' is not spontaneous either.