Question

In the PhET Reactions & Rates (http://openstaxcollege.org/l/16PHETreaction) interactive, on the Many Collisions tab, set up a simulation with 15 molecules of A and 10 molecules of BC. Select “Show Bonds” under Options.

1. Leave the Initial Temperature at the default setting. Observe the reaction. Is the rate of reaction fast or slow?
2. Click “Pause” and then “Reset All,” and then enter 15 molecules of A and 10 molecules of BC once again. Select “Show Bonds” under Options. This time, increase the initial temperature until, on the graph, the total average energy line is completely above the potential energy curve. Describe what happens to the reaction

Short answer

1. At default temperature, the rate of reaction is slow.
2. On increasing temperature, the rate of reaction becomes fast.

Step-by-step solution

 Default temperature 

At the default temperature, the rate of reaction is slow. Molecules of A collide with BC molecules quite frequently; less molecule of them has sufficient energy to make a bond.

At default temperature, reactant molecules have low kinetic energy and low velocity, so the collision of reactant molecules are not much effective in making more bonds. Hence, the formation of product molecules occurs at a slow rate. Therefore, the rate of reaction is slow.

High temperature 

With the increase in temperature, the particle average velocity increases. The average kinetic energy of particles is also increased. The result is that the particle will collide more frequently and move around faster. This results in the encounter of more reactant particles.

Thus, on increasing temperature, the reaction rate increases because the reactant molecules collide at a faster rate at the high temperature, and their colloids result in the formation of products.

The molecule of reactants decreases when the molecule of products increases. After a while, there is ideally an equal amount of BC, AB, and C in the mixture with a slightly large amount of A.