submit when you are finished with questions carefully, some questions have molar Question 31 Which of the following is evidence that a chemical reaction has occurred? O A solid is formed in the reaction. zzes O All of these are evidence that a chemical reaction has occured. Modules O Gas bubbles are observed in the reaction. Chat O The temperature of the reaction goes up by 20 degrees. gle Drive O A color change is noticed in the reaction vessel. Previous Ma ions

The boxes shown below represent a set of initial conditions for the reaction: Draw a quantitative molecular picture that shows what this system looks like after the reactants are mixed in one of the boxes and the system reaches equilibrium. Support your answer with calculations. Consider an equilibrium mixture of four chemicals (A, B, C, and D, all gases) reacting in a closed flask according to the foll owing equation: A+BC+D a. You add more A to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is re-established? Justify your answer. b. You have the original set-up at equilibrium, and add more D to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is re-established? Justify your answer.

. Before two molecules can react, chemists envision that the molecules must first collide with one another. Is collision among molecules the only consideration for the molecules to react with one another?

. Explain what it means that a reaction has reached a state of chemical equilibrium. Explain why equilibrium is a dynamic state: Does a reaction really “stop” when the system reaches a state of equilibrium? Explain why, once a chemical system has reached equilibrium, the concentrations of all reactants remain constant with time. Why does this constancy of concentration not contradict our picture of equilibrium as being dynamic? What happens to the rates of the forward and reverse reactions as a system proceeds to equilibrium from a starting point where only reactants are present?