U N I T T E S T P R A C T I C E

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1 South Pasadena Honors Chemistry Name 4 Salts and Solutions Period Date U N I T T E S T P R A C T I C E You may use a pencil, eraser, and scientific calculator to complete the test. You will be given a periodic table. The solubility rules are listed at the end of the test. No other resources are allowed. Please transfer your answers for Multiple Choice and Matching questions onto the Answer Document. Work for these questions will not be graded. However, sufficient and appropriate work must be shown for the Free Response questions in order to receive full credit. SECTION 1: A, B, or C. Determine whether each description refers to an acidic, basic, or neutral solution. (1 point each) (A) (B) (C) 1. Is purple with cabbage juice. Acidic Basic Neutral 2. Has a ph > 7.0. Acidic Basic Neutral 3. Often tastes bitter. Acidic Basic Neutral 4. Lye (drain cleaner). Acidic Basic Neutral 5. A solution of HNO 3. Acidic Basic Neutral 6. [H ] = [OH ]. Acidic Basic Neutral SECTION 2: TRUE/FALSE. (1 point each) Evaluate the statement in column 1. If it s TRUE, fill in bubble A. If it s FALSE, fill in bubble B. Evaluate the statement in column 2. If it s TRUE, fill in bubble C. If it s FALSE, fill in bubble D. If column 2 is the correct explanation for column 1, then bubble E. If both columns are TRUE, but column 2 is the correct explanation, bubble ACE. If both columns are TRUE, but column 2 is not the correct explanation, bubble AC. If column 1 is TRUE and column 2 is FALSE, bubble AD. If column 1 is FALSE and column 2 is TRUE, bubble BC. If column 1 is FALSE and column 2 is FALSE, bubble BD. Column 1 Column 2 7. CN is a base BECAUSE it cannot donate an H. AC (True True Incorrect Explanation) 8. An aqueous solution of potassium chloride BECAUSE the salt dissolves completely in solution. is a non-electrolyte BC (False True) 9. Ammonia will turn green/blue in red cabbage juice AC (True True Incorrect Explanation) BECAUSE its conjugate acid is NH 4.

2 SECTION 3: MULTIPLE CHOICE. Select the best answer choice for each question. (1 point each) 10. The solution shown to the right can be considered (A) Unsaturated (B) Saturated (C) Supersaturated (D) It cannot be determined 11. According to the solubility curve, approximately how many more grams of potassium nitrate can be dissolved in 40 g water at 70 C than at 40 C? (A) 28 g (B) 50 g (C) 70 g (D) 130 g 12. Beaker A contains a saturated solution of NaCl dissolved in 50 g water, while Beaker B contains a saturated solution of NaCl in 100 g water. If solutions for both beakers are at the same temperature, which of the following is greater in Beaker B than in Beaker A? I. The ratio of the mass of dissolved NaCl to the mass of water. II. The mass of solute particles. III. The molar mass of water. (A) I only. (B) II only. (C) II and III only. (D) I, II, and III. 13. In which of these conditions is CO 2 LEAST soluble in water? (A) Temperature = 10 C Pressure = 1.0 atm (B) Temperature = 10 C Pressure = 4.0 atm (C) Temperature = 50 C Pressure = 1.0 atm (D) Temperature = 50 C Pressure = 4.0 atm 14. Which one of these compounds is least soluble in water? (A) Hexane (non-polar) (B) Nitrous acid (C) Potassium carbonate (D) Sucrose, C 12 H 22 O 11 (polar) 15. Which one of these compounds does not dissolve in water? (A) Ammonium phosphate (B) Calcium carbonate (C) Potassium chromate (D) Zinc nitrate 16. What is the concentration of a solution made by dissolving 12 grams NaOH in enough water to make 0.50 L of solution? Molar mass of NaOH = 40 g/mole (A) 0.60 M (B) 0.30 M (C) 1.2 M (D) 6.0 M 17. List the following solutions with an unknown solute in increasing concentration. X: g solute in a 500 ml solution Y: g solute in a 250 ml solution Z: g solute in a 250 ml solution (A) X < Y < Z (B) X < Z < Y (C) Y < X < Z (D) Y < Z < X 18. A 100 ml sample of a solution with a concentration of 5.00 M is diluted by adding 300 ml of distilled water. The new concentration will be (A) 1.25 M (B) 1.66 M (C) 15.0 M (D) 20.0 M

3 19. If 50 ml of a 200 ml sample of 0.10 M sodium chloride solution is spilled, what is the concentration of the remaining solution? (A) M (B) M (C) 0.10 M (D) 0.20 M 20. Which of the following substances is a base? (A) Ca(OH) 2 (B) C 2 H 5 OH (C) H 2 SO 4 (D) HC 2 H 3 O A property of acids is that they (A) feel slippery. (B) neutralize water. (C) taste bitter. (D) taste sour. 22. According to Svante Arrhenius, acids are substances that (A) decrease the [H ] (B) decrease the [OH ] (C) increase the [H ] (D) increase the [OH ] 23. Each of the following can describe an aqueous solution with a strong electrolyte EXCEPT: (A) The solute dissociates completely into ions. (B) The solute is a covalent compound (C) The solute is a strong acid. (D) The solution contains a large amount of ions. 24. A substance that turns cabbage juice blue and only slightly lights up a light bulb is a: (A) strong acid (B) strong base (C) weak acid (D) weak base 25. A solution has an [H ] = M. What is the [OH ]? (A) M (B) M (C) M (D) M 26. What is the hydrogen ion concentration, [H ], of a solution in which the poh is 9? (A) M (B) M (C) M (D) M 27. Which of the following solutions may have a ph = 8.0? (A) Ammonia (B) Pool acid (C) Rubbing alcohol (D) Vinegar 28. In the reaction below, which is the conjugate acid? CH 3 NH 3 OH CH 3 NH 2 H 2 O (A) CH 3 NH 3 (B) OH (C) CH 3 NH 2 (D) H 2 O 29. Which is the following is NOT a correct conjugate acid-base pair? (A) CH 3 COOH / CH 3 COO (B) H 2 CO 3 / HCO 3 (C) H 3 O / OH (D) NH 4 / NH Which of the following solutions is expected to have the lowest ph? (A) M HNO 2 K a = (B) M HC 2 H 3 O 2 K a = (C) M HOCl K a = (D) M HCN K a = Which of the following is the correct expression for K a for the dissociation of weak base ammonia? NH 3 (aq) H 2 O (l) NH 4 (aq) OH (aq) [NH 3 ] (A) [NH 4 ][OH ] (B) [NH 3][H 2 O] [NH 4 ][OH ] (C) [NH 4 ][OH ] [NH 3 ] (D) [NH 4 ][OH ] [NH 3 ][H 2 O]

4 SECTION 4: FREE RESPONSE. Show all your work to receive full credit. 32. Use the solubility curve to the right to answer the following questions. (a) How many grams of potassium chloride can dissolve in 80 g water at 80 C? (2 points) 50 g KCl 100 g H 2 O = x g KCl 80 g H 2 O x = 40 g KCl (b) How many grams of potassium nitrate will precipitate out when a saturated solution with 600 g water at 80 C is cooled to 50 C? (4 pts) At 80 C: 170 g KNO g H 2 O = x g KNO g H 2 O x = 1020 g KNO 3 80 g KNO 3 At 50 C: 100 g H 2 O = x g KNO 3 x = 480 g KNO 600 g H 2 O g KNO g KNO 3 = 540 g KNO 3 will precipitate out. 33. What is the concentration of a solution when mol KBr is used to prepare a 600 ml solution (4 points) n = mol V = 600 ml = L M =? [KBr] = n V = mol L = M 34. How many grams of Ca(NO 3 ) 2 is needed to prepare 120 ml of a M solution? (4 points) n =? V = 120 ml = L [Ca(NO 3 ) 2 ] = M n = V M = (0.120 L) mol = mol L Molar Mass = 1(40.08) 2(14.01) 6(16.00) = g/mol m = mol g = 2.95 g mol 35. How many ml of a 6.0 M HCl solution are needed to prepare ml of a M solution? (4 points) M conc = 6.0 M (M conc )(V conc ) = (M dil )(V dil ) V conc =? ml V conc = (M dil)(v dil ) (0.800 M)(120.0 ml) = (M conc ) (6.0 M) M dil = M V dil = ml = 16.0 ml 36. Complete the following table. No work is needed. (16 points total; 1 per box) [H ] [OH ] ph poh Acid/Base/Neutral (a) M M Acid (b) M M Base (c) M M Acid (d) M M Acid

5 37. Find the ph of a M solution of HNO 3. (6 points) HNO 3 (aq) H (aq) NO 3 (aq) Initial M 0 M 0 M Change M M M Final 0 M M M [H ] = M ph = log (0.0150) = Given a M solution of benzoic acid, HC 7 H 6 O 2. The K a of benzoic acid is (a) Write the dissociation equation for benzoic acid, and the expression for its K a. (4 points) HC 7 H 6 O 2 (aq) H (aq) C 7 H 6 O 2 (aq) K a = [H ][C 7 H 6 O 2 ] = [HC 7 H 6 O 2 ] 5 (b) Find the ph and poh of this solution. (6 points) HC 7 H 6 O 2 (aq) H (aq) C 7 H 6 O 2 (aq) Initial M 0 M 0 M Change x x x Equil x x x [H ] = x = M ph = log ( ) = 2.41 K a = [H ][C 7 H 6 O 2 ] = [HC 7 H 6 O 2 ] 5 (x)(x) (0.240 x) = x 2 = Because this is a weak acid, we can assume that x is very small compared to 0.240, so (0.240 x) x = (c) Find the % dissociation of this solution. (2 points) % dissociation = x i 100% = M M 100% = 1.6 % 39. Find the concentration of all the ions in a M solution of sodium phosphate. (4 points) Na 3 PO 4 (s) 3 Na (aq) PO 3 4 (aq) Initial M 0 M 0 M Change M M M Final 0 M M M [Na ] = M [PO 4 3 ] = M Solubility Rules for Salts Always soluble: alkali ions, NH 4, NO 3, ClO 3, ClO 4, C 2 H 3 O 2, HCO 3 Generally soluble: Cl, Br, I Soluble except with Ag, Pb 2 2, Hg 2 F Soluble except with Pb 2, Ca 2, Ba 2, Sr 2, Mg 2 2 SO 4 Soluble except with Pb 2, Ca 2, Ba 2, Sr 2 Generally insoluble: O 2, OH Insoluble except with Ca 2, Ba 2, Sr 2, alkali ions, NH 4 CO 2 3, PO 3 4, S 2, SO 2 3, CrO 2 2 4, C 2 O 4 Insoluble except with alkali ions and NH 4 Strong Acids HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 3, HClO 4, HIO 4 Strong Bases LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2 Gases that Form H 2 S (g) H 2 CO 3 (aq) CO 2 (g) H 2 O (l) H 2 SO 3 (aq) SO 2 (g) H 2 O (l) NH 4 OH (aq) NH 3 (g) H 2 O (l)