HW: Collision Theory and Energy of Reactions

1. Lab Scenario Nancy placed 20 drops of 1M HCl into a test tube, and then placed 20 drops of 3M HCl into a second test tube. She then cut a magnesium strip into 1 cm strips. She placed a strip into each test tube at the same time. Which test tube should she expect for the magnesium to react faster and ultimately disappear first? Explain your answer. 2. Oliver poured 25 mL of hydrogen peroxide into a beaker. He noticed that nothing was happening in the beaker, or so it seemed to the naked eye. He then added manganese dioxide to the beaker and noticed an immediate reaction and saw bubbles and fizz. What was the role of manganese dioxide in this experiment? it was acting as a catalyst it increased the concentration of the hydrogen peroxide it warmed the hydrogen peroxide Use the graph below to answer questions 3-4. 3. Which number indicates the activation energy? 1 2 3 4 4. Which number indicates the overall change in energy? 1 2 3 4 5. Graph B shows the energy involved in the following chemical reaction: H2 + I2 →2HI Label the reactants and products in graph B. Use the words "reactants" and "products." reactants products 6. Using the graph from question #5, answer the following questions. How much energy is contained in the reactants in this reaction? ~3.2kcalHow much energy is contained in the products in this reaction?~1.5kcalWhat is the activation energy in this reaction? ~0.8kcalIs this an endothermic reaction or an exothermic reaction? exothermic reactionAccording to your answer above, does that mean the reaction absorbs energy or releases energy? releases energyWhat is the overall change in enthalpy (energy)? (Be sure to include the + or - sign). ~ -1.7 kcal 7. Use the graph from question #5 to answer this question. Explain how a catalyst would affect the activation energy. 8. Which of the following factors would slow down the rate of a reaction? adding a catalyst decreasing the concentration increasing the surface area cooling the temperature 9. True or False? Sort the following statements as true or false. True Reactants must have enough energy when colliding in order to form product Reactants need to be in the correct orientation when colliding in order to form product A larger surface area means that more molecules are exposed More molecules means higher chance of collisions False Most collisions produce reactions A catalyst is needed at all times in order for a collision to occur There are less collisions when molecules move faster 10. What are the correct units for molarity? mol g mol 11. Calculate the molarity. Consider significant digits. a) Calculate the molarity of KI solution that contains 3.75 moles in a volume of 5.3 L: 0.71Mb) Calculate the molarity of BaS solution that contains 0.82 moles in a volume of 510 mL: 1.6 M