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Equilibrium Problems
Uploaded: A month ago
Contributor: IVANPAN0802
Category: Chemistry
Type: Assignment
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Filename:   Equilibrium HW.pdf (75.78 kB)
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Equilibrium Problems 1. Write the equilibrium expression for each of the following reactions: a. N2 (g) + 3 H2 (g) 2 NH3 (g) b. I2 (s) + Cl2 (g) 2 ICl (g) c. NO2 (g) NO (g) + ½ O2 (g) 2. Calculate Kp for the following equilibrium at 250 °C if Kc = 0.042. PCl5 (g) PCl3 (g) + Cl2 (g) 3. Given the initial partial pressure of (PPCl5) = 0.0500 atm, (PPCl3) = 0.150 atm, and (PCl2) = 0.250 atm at 250 °C for the following reaction, what must each equilibrium partial pressure be? PCl5 (g) PCl3 (g) + Cl2 (g) 4. The reaction NO (g) « N2 (g) + O2 (g) has a value of K= 2400 at 2000 K. If 0.61 g of NO are put in a previously empty 3.00 L vessel, calculate the equilibrium concentrations of NO, N2, and O2. 5. Using the same reaction as in #4, calculate the equilibrium concentrations of NO, N2, and O2 if the initial concentrations of each species are: [NO] = 0 M, [N2] = 0.850 M, [O2] = 0.560 M 6. The reaction of carbon disulfide with chlorine is as follows: CS2 (g) + 3 Cl2 (g) CCl4 (g) + S2Cl2 (g) DH = -238 kJ Predict the effect of the following changes to the system on the direction of equilibrium. A. The pressure on the system is doubled by halving the volume. B. CCl4 is removed as it is generated. C. Heat is added to the system. 7. A supply of NaOH is known to contain the contaminants NaCl and MgCl2. A 4.955 g sample of this material is dissolved and diluted to 500.00 mL with water. A 20.00 mL sample of this solution is titrated with 22.26 mL of a 0.1989 M solution of HCl. What percentage of the original sample is NaOH? Assume that none of the contaminants react with HCl. 8. A mixture of CH4 and H2O is passed over a nickel catalyst at 1000 K. The emerging gas is collected in a 5.00 L flask and is found to contain 8.62 g of CO, 2.60 g of H2, 43.0 g of CH4 and 48.4 g of H2O. Assuming that equilibrium has been reached, calculate Kc and Kp for the reaction. 9. Arrange the following 0.10 M solutions in order of increasing acidity: (i) ammonium nitrate, (ii) sodium nitrate, (iii) ammonium acetate, (iv) sodium fluoride, (v) sodium acetate. 10. Dissolved carbon dioxide in water, CO2(aq), is sometimes regarded as the diprotic acid, carbonic acid, H2CO3(aq). (Ka1 = 4.3 x 10-7, Ka2 = 5.6 x 10-11) Calculate the concentrations at equilibrium of H2CO3, HCO3-, CO32- and H3O+ in a saturated aqueous solution of CO2 in which the original concentration of H2CO3 is 0.034 M. 11. Consider the titration of 60.0 mL of 0.100 M NH3(aq) with 0.150 M HCl. Calculate the pH after the following volumes of titrant have been added: (a) 0 mL; (b) 20.0 mL; (c) 39.5 mL; (d) 40.0 mL; (e) 40.5 mL; (f) 60.0 mL. 12. A hypothetical weak acid, HA, was combined with NaOH in the following proportions: 0.20 mol of HA, 0.080 mol of NaOH. The mixture was diluted to a total volume of 1.000 L and the pH measured. (a) if pH = 4.80, what is the pKa of the acid? (b) How many additional moles of NaOH should be added to the solution to increase the pH to 5.00? 13. What volume of 0.120 M NaOH must be added to 100 mL of 0.100 M NaHC2O4 to reach a pH of 4.70? 14. A buffer solution is prepared by dissolving 1.51 g each of benzoic acid and sodium benzoate in 150.0 mL of solution. (a) What is the pH of this buffer solution? (b) Which buffer component must be added, and in what quantity, to change the buffer pH to 4.00? (c) What quantity of 2.0 M NaOH or 2.0 M HCl must be added to the original buffer to change the pH to 4.00? 15. Compound X decomposes upon heating according to the following equation: 2 X (s) Y (g) + 2 Z (g) When 5 mol of X were put in a 1 dm3 container and heated, the equilibrium mixture contained 0.6 mol of Y. What is the approximate numerical value of the equilibrium constant Kc? 16. A 0.831 g sample of SO3 is placed in a 1.00 L container and heated to 1100 K. The SO3 decomposes to SO2 and O2. At equilibrium, the total pressure is 1.300 atm. Find the values of Kp and Kc for this reaction at 1100 K. 17. (a) Calculate the percent ionization of 0.125 M lactic acid. (b) Calculate the percent ionization of 0.125 M lactic acid in a solution containing 0.0075 M sodium lactate. 18. A 0.25 M solution of a salt NaA has a pH = 9.29. What is the value for the conjugate acid Ka? 19. The Kb for methylamine (CH3NH2) at 25 °C can be found in your textbook. (a) Write the chemical equation for the equilibrium that corresponds to Kb. (b) By using the Kb value, calculate DG ° for the equilibriumin part (a). (c) What is the value of DG at equilibrium? (d) What is the value of DG when [H+] = 6.7 x 10-9 M, [CH3NH3+] = 2.4 x 10-3 M and [CH3NH2] = 0.098 M? 20. Calculate the molar solubility of the following compounds: -14 a. PbCO3 Ksp = 7.4 x 10 -12 b. Ag2CrO4 Ksp = 1.3 x 10 -11 c. La(IO3)3 Ksp = 1.2 x 10 -36 d. Fe3(PO4)2 Ksp = 1.0 x 10 21. Convert the molar solubility of each compound in problem 1 to the solubility expressed in grams /L. 22. If the carbonate ion concentration in a saturated lead(II) carbonate solution is adjusted to 0.020 M, what is the concentration of lead(II) ion in solution? How does this quantitatively demonstrate -14 LeChatelier’s Principle? Kxp for lead(II) carbonate is 7.4 x 10 2+ 2+ 23. Carbonate ion is added drop wise to a solution containing 0.30 M Ca and 0.30 M Ni . The Ksp for -9 -7 CaCO3 is 4.5 x 10 and the Ksp for NiCO3 is 1.3 x 10 . a. Which cation will precipitate first? b. What will be the concentration of the less soluble cation remaining in solution when the more soluble cation begins to precipitate? 24. What is the concentration of Co(III) ions in solution if the pH of the solution is 9.00? -45 Ksp for Co(OH)3 = 3.0 x 10 -4 -5 25. Will a precipitate form if 400 mL of 2.0 x 10 M Ca(NO3)2 is mixed with 600 mL of 1.5 x 10 M -8 KIO3? Ksp of Cd(IO3)2 = 2.3 x 10 -3 -4 26. Will a precipitate form if 300 mL of 5.0 x 10 M Ca(NO3)2 is mixed with 400 mL of 3.5 x 10 M -9 Na2CO3? Ksp of CaCO3 = 4.5 x 10 2+ 27. a. When additional Ba ions are added to a saturated Ba3(PO4)2, one observes additional precipitate from in the container. Explain this observation in terms of LeChatelier’s Principle. b. When a saturated solution of Ba3(PO4)2 is acidified, the precipitate dissolves. Explain. c. When the solution from 10 b. is treated with base, the precipitate reappears. Explain.
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