AP Chemistry Review Packet # form B. How many grams of water are present in 1.00 mol of copper(ii) sulfate pentahydrate?

Transcription

1 AP Chemistry Review Packet #4 Warmup: Reaction Prediction 2010 form B (a) Solid copper(ii) sulfate pentahydrate is gently heated. How many grams of water are present in 1.00 mol of copper(ii) sulfate pentahydrate? (b) Excess concentrated aqueous ammonia is added to a solution of nickel(ii) nitrate, leading to the formation of a complex ion. Which of the reactants acts as a Lewis acid? (c) Methylamine (CH 3 NH 2 ) is added to a solution of hydrochloric acid. Methylamine dissolves in water to form a solution. Indicate whether this solution is acidic, basic, or neutral.

2 Mock FR

3 2011 A form B (calculator) 2. An 8.55 mol sample of methanol, CH 3 OH, is placed in a 15.0 L evacuated rigid tank and heated to 327 C. At that temperature, all of the methanol is vaporized and some of the methanol decomposes to form carbon monoxide gas and hydrogen gas, as represented in the equation below. CH 3 OH(g) CO(g) + 2 H 2 (g) (a) The reaction mixture contains 6.30 mol of CO(g) at equilibrium at 327 C. Calculate the number of moles of H 2 (g) in the tank. Calculate the number of grams of CH 3 OH(g) remaining in the tank. (iii) Calculate the mole fraction of H 2 (g) in the tank. (iv) Calculate the total pressure, in atm, in the tank at 327 C. (b) Consider the three gases in the tank at 327 C: CH 3 OH(g), CO(g), and H 2 (g). How do the average kinetic energies of the molecules of the gases compare? Explain. Which gas has the highest average molecular speed? Explain. (c) The tank is cooled to 25 C, which is well below the boiling point of methanol. It is found that small amounts of H 2 (g) and CO(g) have dissolved in the liquid CH 3 OH. Which of the two gases would you expect to be more soluble in methanol at 25 C? Justify your answer.

4 2010 A 8 H + (aq) + 4 Cl - (aq) + MnO 4 - (aq) 2 Cl 2 (g) + Mn 3+ (aq) + 4 H 2 O(l) 3. Cl 2 (g) can be generated in the laboratory by reacting potassium permanganate with an acidified solution of sodium chloride. The net-ionic equation for the reaction is given above. (a) A ml sample of M NaCl reacts completely with excess KMnO 4 (aq). The Cl 2 (g) produced is dried and stored in a sealed container. At 22 C the pressure of the Cl 2 (g) in the container is atm. Calculate the number of moles of Cl - (aq) present before any reaction occurs. Calculate the volume, in L, of the Cl 2 (g) in the sealed container. An initial-rate study was performed on the reaction system. Data for the experiment are given in the table below. Trial [Cl - ] [MnO - 4 ] [H + ] Rate of Disappearance of MnO - 4 in M s (b) Using the information in the table, determine the order of the reaction with respect to each of the following. Justify your answers. Cl - MnO 4 - (c) The reaction is known to be third order with respect to H +. Using this information and your answers to part (b) above, complete both of the following: Write the rate law for the reaction. Calculate the value of the rate constant, k, for the reaction, including appropriate units. (d) Is it likely that the reaction occurs in a single elementary step? Justify your answer.

5 4. Reaction Prediction 2009 form B (a) A barium nitrate solution and a potassium fluoride solution are combined and a precipitate forms. If equimolar amounts of barium nitrate and potassium fluoride are combined, which reactant, if any, is the limiting reactant? Explain. (b) A piece of cadmium metal is oxidized by adding it to a solution of copper (II) chloride. List two visible changes that would occur in the reaction container as the reaction is proceeding. (c) A hydrolysis reaction occurs when solid sodium sulfide is added to distilled water. Indicate whether the ph of the resulting solution is less than 7, equal to 7, or greater than 7. Explain.

6 B (no calculator) A solution of M HCl and a solution of M NaOH are prepared. A 40.0 ml sample of one of the solutions is added to a beaker and then titrated with the other solution. A ph electrode is used to obtain the data that are plotted in the titration curve shown. (a) Identify the solution that was initially added to the beaker. Explain your reasoning. (b) On the titration curve above, circle the point that corresponds to the equivalence point. (c) At the equivalence point, how many moles of titrant have been added? (d) The same titration is to be performed again, this time using an indicator. Use the information in the table below to select the best indicator for the titration. Explain your choice. Indicator ph Range of Color Change Methyl violet Methyl red 4-6 Alizarin yellow (e) What is the difference between the equivalence point of a titration and the end point of a titration? (f) On the grid provided, sketch the titration curve that would result if the solutions in the beaker and buret were reversed (i.e., if 40.0 ml of the solution used in the buret in the previous titration were titrated with the solution that was in the beaker).

7 2010 B 6. Use the information in the table below to respond to the statements and questions that follow. Your answers should be in terms of principles of molecular structure and intermolecular forces. Compound Formula Lewis Electron-Dot Diagram Ethanethiol CH 2 CH 2 SH Ethane CH 3 CH 3 Ethanol CH 3 CH 2 OH Ethyne C 2 H 2 (a) Draw the complete Lewis electron-dot diagram for ethyne in the appropriate cell in the table above. (b) Which of the four molecules contains the shortest carbon-to-carbon bond? Explain. (c) A Lewis electron-dot diagram of a molecule of ethanoic acid is given below. The carbon atoms in the molecule are labeled x and y, respectively. Identify the geometry of the arrangement of atoms bonded to each of the following. Carbon x Carbon y (d) Energy is required to boil ethanol. Consider the statement "As ethanol boils, energy goes into breaking C-C bonds, C- H bonds, C-O bonds, and O-H bonds." Is the statement true or false? Justify your answer. (e) Identify a compound from the table above that is nonpolar. Justify your answer. (f) Ethanol is completely soluble in water, whereas ethanethiol has limited solubility in water. Account for the difference in solubilities between the two compounds in terms of intermolecular forces.