Honors Chemistry Unit 4 Exam Study Guide Solutions, Equilibrium & Reaction Rates

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1 Honors Chemistry Unit 4 Exam Study Guide Solutions, Equilibrium & Reaction Rates Define the following vocabulary terms. Solute Solvent Solution Molarity Molality Colligative property Electrolyte Non-electrolyte Freezing-point depression Boiling-point elevation Solubility Saturated Unsaturated Supersaturated Collision theory Rate Activation Energy Reversible reaction Chemical equilibrium Dynamic Equilibrium constant LeChatelier s Principle Conceptual Review 1. Write the equation for molarity and identify each variable. 2. Write the equation for molality and identify each variable. 3. Write the equation for freezing point depression and identify each variable. 4. Write the equation for boiling point elevation and identify each variable.

2 5. How many particles would each of the following compounds produce in solution? a. CaCl 2 b. C 12H 22O 11 c. CH 4 d. NaCl e. C 6H 12O 6 f. Al 2O 3 6. Describe why an ionic compound affects the colligative properties of a solution more than a covalent compound. 7. Describe the difference between a saturated, unsaturated and supersaturated solution. 8. Describe how you can determine if a solution is saturated, unsaturated, or supersaturated using a solubility curve. 9. Describe collision theory and why the rate of a reaction is dependent upon it. 10. List the 5 factors that affect reaction rates and describe how they affect the reaction rate: a. b. c. d. e.

3 11. List the conditions necessary for chemical equilibrium. 12. Describe how the forward and reverse reaction rates are related once a reaction reaches equilibrium. Draw a graph to describe this relationship when a system is at equilibrium. 13. Describe how activation energy of the forward and reverse reactions and ΔH are related. 14. Describe how the equilibrium constant, K eq, can predict if the products or reactants are favored at equilibrium. 15. Describe the relationship between K eq and temperature for both an endothermic and exothermic reaction.

4 16. Describe LeChatelier s Principle and fill in the following charts. Stress Reactant/Product / Equilibrium Shift Concentration Reactant Reactant Product Product Stress Exothermic/Endothermic / Equilibrium Shift Temperature Endothermic Endothermic Exothermic Exothermic Stress / Equilibrium Shift Pressure Practice Questions & Calculations 1. Calculate the boiling point of a solution of 27g of C 6H 12O 6 in 1000g of water. (K b = C/m) 2. Calculate the freezing point of an aqueous solution of 65.2g CaCl 2 in 400g of water. (Kf = 1.86 C/m)

5 Use the following solubility curve to answer questions Which salt is most soluble at 60 C? 4. What mass of KNO 3 must be dissolved in 100g of water at 20 C to create a saturated solution? 5. A solution of Potassium Bromide, KBr, is made by dissolving 40 grams of the salt in 100g of water at 25 C. How much more salt must be added to create a saturated solution? 6. What mass of NaClO 3 must be dissolved in 500g of water to create a saturated solution at 80 C?

6 For questions 7-13, place a check mark on the line when the situation will cause an increase in the reaction rate. 7. Changing temperature of the reactants from 75 C to 150 C. 8. Grinding a solid into fine particles before reacting it. 9. Diluting a solution before adding another reactant. 10. Allowing a gas to expand and take up more volume. 11. Adding a catalyst. 12. Changing the concentration of the reactants from 0.1 M to 0.5M. 13. Mixing two chemicals together and then placing the reaction vessel in the freezer. 14. Given the following equation, describe the relationship between the rate of formation of CO 2 and the rate of disappearance of C 8H 18. 2C 8H 18 (l) + 25O 2 (g) 16CO 2 (g) + 18H 2O (l) Use the data in the table for the following balanced reaction to answer questions What is the rate of disappearance of HCl in the initial 100 seconds? 16. What is the rate of disappearance of HCl between 400 and 600 seconds? 2HCl Cl2 + H2 Concentration of HCl (mol/l) Time (s) What is the rate of disappearance of HCl between 200 and 300 seconds? 18. What concentration of Cl 2 will remain after 500 seconds? 19. What concentration of H 2 will remain after 200 seconds?

7 20. For the reaction MgSO 4 (aq) + 2 NaCl (aq) MgCl 2 (aq) + Na 2SO 4 (aq), Δ[NaCl]/Δt was found to be 4.32 M/s after 300 seconds where Δ[NaCl] is the change in concentration of sodium chloride. Determine the Δ[MgCl 2]/Δt for the reaction at the same time. Use the following graph to answer questions H2O H2 + ½ O2 21. Which line represents H 2O? 22. Which line represents H 2? 23. Which line represents O 2? 24. Calculate the ΔH (energy of the reaction) if the activation energy in the forward direction is 250kJ and the activation energy of the reverse reaction is 475kJ. 25. Why is chemical equilibrium described as dynamic? 26. Identify where this reaction reaches equilibrium on the following graph.

8 27. What causes a change in K eq? 28. Given the following equation, what conditions would favor the production of HI? 12.6 kcal + H 2 (g) + I 2 (g) 2HI (g) 29. Given the following reaction that is exothermic, what changes will favor the production of N 2? N 2 (g) + 3H 2 (g) 2NH 3 (g) Using LeChatelier s Principle, complete the following chart for the balanced reaction. NH 3 (g) + HCl (g) NH 4Cl (s) + energy (heat) Stress Equilibrium Shift [NH 3] [HCl] [NH 4Cl] Concentration NH 3 Right s s Concentration HCl Concentration NH 4Cl Concentration NH 3 Concentration HCl Concentration NH 4Cl temperature temperature pressure pressure