Which type of graph is best used to show the percentage of reactant molecules that collide during a reaction?
scatter plot
circle graph
stem and leaf plot

Circle Graph

Explanation:

A scatter plot shows distribution of some numbers or properties versus another property. So it should be used for analysis of distribution or probability of something.

Stem and leaf plot are used when we have to show splitting of a stem ( a number) into leaves (another numbers).

So for percentage of reactant molecules colliding cannot be represented by scatter plot or stem and leaf plot.

In a circle graph or pie chart, we divide a circle (considering it to be 100%) into different parts based on fraction or percentage of each component.

For percentage of reactant molecule, we can divide the whole circle into two parts. One part showing the percentage of non reacting molecules and other part showing the percentage of reactant molecules undergoing collision.