Advanced Applications of Chemical Reactions

KEY Name:____________________ Per:______ Unit 8 Outline- Advanced Applications of Chemical Reactions Study Guide 1. According to the collision theory, what 3 things must happen in order for two molecules to react? - collide -collide with enough energy - with the correct alignment 2. Using the collision theory, explain if the following would increase/ decrease the rate of reaction and why: 2 HCl(aq) + Mg(s) 🡪 MgCl2(aq) + H2(g) a. Increase temp: Increase reaction, molecules collide more often & more energy due to greater velocity b. Increase HCl: Increase reaction, more collisions because more reactants to collide with c. Increase pressure: Pressure only affects gases. This one is tough & more difficult than will be on your test. Pressure wouldn’t affect the reactants directly because none of them are gases. One of the products is a gas, so it might cause the gas particles to collide more with the reactants and could slow down the reaction. d. Remove MgCl2 : Increase reaction, less products means less chance for them to interfere with collisions occurring between reactants e. Add H2 : Decrease, more products mean they interfere more with reactants and the reactants would collide less. 3. Identify the following on the graphs (with # or letter): 1 a. Reactantsb. Products- 2 c. Activation energy (number/letter & amount in Joules)- (300 Joules) d. e. Is this reaction exothermic or endothermic? What is the ΔH for this reaction? Endothermic How much energy is absorbed or released. …C on graph (200 Joules) 4. Explain how a catalyst affects the activation energy in a chemical reaction. (Also, show on the above graph what a catalyst might do). Speeds it up by lowering the activation energy. (see line on graph) 5. What is the importance of the activation energy in a chemical reaction? Amount of energy needed for a reaction to occur. 6. Using your references, calculate the heat of reaction (ΔH = ) for the following reaction: H2 (g) + Cl2 (g) 🡪 2HCl (g) Reactants: (Bonds broken) Products (Bonds formed) 1 H-H 435 kJ x 1 = 435 kJ 2 H-Cl 439 kJ x 2 = 878 kJ 1 Cl-Cl 243 kJ x 1 = 243 kJ Total = 678 kJ energy in solve for ΔH = Total = 878 kJ energy out (Bonds broken- bonds formed)… 678 KJ- 878 KJ = -200 KJ Write the heat Equation: H2 (g) + Cl2 (g) 🡪 2HCl (g) + 200 KJ (write it on the product side because heat exits the reaction, is a product) a. b. c. d. e. Draw in the other side of the graph Label on the graph where the bonds are breaking Label on the graph where bonds are forming Label the ΔH on the graph Is this endothermic or exothermic? EXO… More energy being released than used to break bonds. 7. Use the Le Chatelier’s principle to predict how the system at equilibrium would shift and why: CO (g) + 3 H2 (g) 🡨 🡪 CH4 (g) + H2O (l) + 113 J Stresses: a. adding CO Shifts 🡪 to use up extra CO b. Removing water Shifts 🡪 to make more H2O c. Adding pressure Shifts 🡪 reduce pressure because only 1 gas particle is made going in the forward direction, while going in the reverse produces 4 gas particles. d. Adding heat Shifts 🡨 use up heat 8. Use the following unbalanced equation to answer the questions below: 1 SiO2(s) + 4 HF(g) 🡪 1 SiF4(g) + 2 H2O(l) a. What is the mole ratio between: SiO2 & H2O ? 1 mole SiO2 2 mole H2O SiO2 & HF? 1 moleSiO2 4 mole HF b Given 3 moles of HF, how many moles of H2O are produced? 3 mol HF 2 mol H2O 4 mol HF 1.5 mol H2O c. Given 10 grams of silicon dioxide how many grams of HF are needed? 10 g SiO2 mol SiO2 4 mol HF 20.01 g HF 60.09 g SiO2 1 mol SiO2 1 mol HF = 13 g HF 2CuO + 2SO2 9. 2CuS + 3O2 🡪 a. If 100 g of CuS are available, how much sulfur dioxide (grams) can be produced? 100 g CuS 1 mol CuS 2 mol SiO2 64 g 95.62 g CuS 2 mol CuS 1 mol SO2 = 66.93 g SO2 b. In a lab, you produced 60 grams of sulfur dioxide as described in the reaction above. I.What is the theoretical yield (from calculations above)? 66.93 g (stoich answer) II. What is the actual yield (aka experimental yield) (given above)? III.Calculate the percent yield (equation on lab)? 60 g (lab results) 60/ 66.93 = .896 x 100= 89.6%