The graph shows the potential energy diagram for an unknown chemical change. a graph is shown with an inverted graph curve. the curve starts at a higher position on the left side and ends at a lower position on the right side. the higher left side position has reactants written below it and the lower right side position has products written below it. the y axis of the graph has the title potential energy with kj written in parentheses. there is an arrow pointing upwards which is parallel to the y axis. the x axis of the graph has reaction pathway along with an arrow pointing towards the right. which chemical change could the graph represent? photosynthesis in plants combustion of propane gas electrolysis of sodium chloride adding heat to decompose calcium carbonate

The graph can be pictured as shown in figure

As shown in figure the energy of reactants is more than the energy of products

Thus the enthalpy of reaction will be negative or we can say that as the energy of products is less than the energy of reactants the reaction is exothermic

Now let us consider each of the given reaction system

a) photosynthesis: in this process plants convert carbon dioxide and water to glucose in presence of sunlight. so the reaction is endothermic in nature, Hence the graph could not be of photosynthesis

b) combustion : combustion is burning of substance in presence of oxygen and this is with the release of energy in the form of light or heat

Thus this is an exothermic reaction. Hence graph can be of combustion of propane

c)  Electrolysis of NaCl: this process also requires energy thus it is an endothermic reaction. Hence the graph could not be of this reaction.

d) Heat to decompose calcium carbonate: thus again it is an endothermic reaction.Hence the graph could not be of this reaction.

it is the most commonly accepted one