What do the peaks on the graphs in figure 7-3 represent

The given graphs are Reaction Coordinate Diagrams which depict the conversion of reactants into products.

Diagram 1: Represents an exothermic reaction. These reactions proceed with the release of heat energy as a result the energy of the products is lower than the reactants.

Diagram 2: Represents an endothermic reaction. In contrast, these reactions proceed with the absorption of heat energy as a result the energy of the products is higher than the reactants.

In both diagrams, there is a peak or a hump which corresponds to the activation energy for the reaction. This is the minimum amount of energy required by the reactants as they collide to form the products.

hey there!

mass = 6.75 g

volume =   9 cm³

therefore:

d = mass / volume

d   = 6.75 / 9

d = 0.7 g/cm³

answer b