Question

Which piece of evidence would prove that a reaction is exothermic?

There is a phase change during the reaction.
One of the reactants is baking soda.
The reactants have more energy than the products.
There are more moles of gas in the products than in the reactants.

Answer 1

The reactants have more energy than the products.

Answer 2

The reactants have more energy than the products. If a reaction is EXOthermic, it loses energy during the reaction, so the output (products) will have less energy than the input (reactants).