Public Review Acids and Bases June 2005 13. A solution of which ph would make red litmus paper turn blue? 2 4 6 8 14. Which is the most recent definition of an acid? Arrhenius Brønsted)Lowry modified Arrhenius operational 15. If their concentrations are equal, which solution will show the highest electrical conductivity? H 3 BO 3 (aq) HCl (aq) H 2 CO 3 (aq) H 2 C 2 O 4 (aq) 16. Which substance, when added to H2SO4(aq), would produce a precipitate and make the solution less acidic? Ca(NO 3 ) 2 LiNO 3 NaOH Sr(OH) 2 17. The table below lists four unknown acids. The ph of a 0.10 mol/l solution for each acid is given. Which conjugate base would have the lowest K b? W (aq) X (aq) Y (aq) Z (aq) 18. What is the K a expression for KMnO 4 (aq)? 19. In the equilibrium below, which two species act as BrønstedLowry bases? H 3 BO 3 and H 2 BO 3 H 3 BO 3 and H 2 S HS and H 2 BO 3 HS and H 2 S
20. What is the poh of a solution if the ph is 2.0? 0.01 0.02 2.0 12.0 21. What is a substance of known purity and molecular mass used to prepare a solution with a precise concentration? buffer indicator primary standard standard solution 22. What is the ph of a 0.050 mol/l Cu(OH) 2 solution? 1.00 1.30 12.70 13.00 23. Which best describes [OH ] and [H 3 O + ] in a sample of pure water at 25.0 o C? 24. The data below was obtained from a titration of acetic acid with sodium hydroxide to the equivalence point. What most likely caused the result in trial 3? All the acid was removed from the pipette. Four drops of indicator was used instead of two. The pipette was rinsed with water before use. The reaction flask was rinsed with water. 25. Which indicator should be used to detect the equivalence point in a titration of hydrofluoric acid with sodium hydroxide? bromocresol green methyl red orange IV thymolphthalein 26. Which titration could result in ph = 4.0 at the equivalence point? 27. What is the [OH ] for an aqueous solution with ph = 3.25? 1.8 x 10 11 mol/l 5.6 x 10 4 mol/l 0.51 mol/l 1.0 mol/l
52.(a) Calculate the ph of a 0.025 mol/l solution of nitrous acid given the Ka for HNO 2 (aq) is 7.2 10 4. (b) (c) The concentration of a solution of arsenic acid, H 3 AsO 4 (aq) is determined by titrating it with sodium hydroxide, NaOH(aq). (i) Write the equation for the overall reaction. (ii) Draw and label a titration curve for the complete titration. A titration was performed by adding 0.115 mol/l NaOH(aq) to a 25.00 ml sample of H 2 SO 4 (aq). Using the data below, calculate the concentration of H 2 SO 4 (aq). (d) The table below shows the results of tests performed on four 0.10 mol/l unknown solutions. Use this data to determine which solution is NaOH(aq) and which is NaCl(aq). Justify your answer. (e) A piece of magnesium is placed in both hydrochloric acid, HCl (aq), and acetic acid, CH 3 COOH (aq), according to the information below. Compare both reactions in terms of reaction rate and amount of hydrogen gas produced. Justify your answer. June 2006 13. Which describes an Arrhenius base? donates H + ions donates OH ions produces H + ions in aqueous solution produces OH ions in aqueous solution 14. In which reaction is water behaving as a BronstedLowry acid? 15. Which is the conjugate acid of HS (aq)? H 3 O + (aq) H 2 S(aq) OH (aq) S 2 (aq)
16. Which is the net ionic equation for the neutralization of CH 3 COOH(aq) with NaOH(aq)? CH 3 COO (aq) + H + (aq) + OH (aq) º CH 3 COO (aq) + H 2 O(l) CH 3 COOH(aq) + NaOH(aq) º H 2 O(l) + NaCH 3 COO(aq) CH 3 COOH(aq) + OH (aq) º H 2 O(l) + CH 3 COO (aq) H + (aq) + OH (aq) º H 2 O(l) 17. Which is the strongest acid and strongest base in the equilibrium below? HY(aq) + Z (aq).. HZ(aq) + Y (aq) K = 7.8 18. According to BrönstedLowry theory, which best represents the selfionization of water? H 2 O(l) º 2 H + (aq) + O 2 (aq) H 2 O(l) º H+(aq) + OH (aq) 2 H 2 O(l) º H3O+(aq) + OH (aq) 2 H 2 O(l) º 2 H2(g) + O 2 (g) 19. Why is the ph of 0.10 mol/l H 3 PO 4 (aq) higher than the ph of 0.10 mol/l HCl(aq)? HC1(aq) ionizes to a greater extent. HC1(aq) is a weaker acid. H 3 PO 4 (aq) has more hydrogen atoms. H 3 PO 4 (aq) is amphoteric in water. 20. What is the poh of 0.050 mol/l NaOH(aq) at 25 o C? 1.00 1.30 12.70 13.00 21. What is the [H3O+] of a solution with ph = 2.81? 6.5 10 12 mol/l 1.5 10 3 mol/l 6.5 10 2 mol/l 1.5 10 11 mol/l 22. Which will cause [H 3 O + ] to decrease and K W to remain constant for the equilibrium below? 2H 2 O(l) + energy > H 3 O + (aq) + OH (aq) adding a strong acid adding a strong base decreasing temperature increasing temperature 23. Which pair represents a possible buffer? HCl(aq) and Cl (aq) HCl(aq) and NaOH(aq) H 2 CO 3 (aq) and HCO 3 (aq) H 2 CO 3 (aq) and NH 3 (aq) 24. The ph values of 0.10 mol/l solutions of four unknown acids are given below. Which conjugate base has the lowest K b? A (aq) B (aq) C (aq) D (aq)
25. What occurs to the indicator equilibrium below when the indicator, HIn, is added to 0.10 mol/l Hcl(aq)? 26. Which is used in a titration to determine the concentration of an acid or base? buffer pipette solution standard solution thermometer 27. If the initial ph of a solution was 11.2 and the ph at the equivalence point was 6.3, which pair was titrated? CH 3 COOH(aq) with NaOH(aq) HCl(aq) with NH 3 (aq) NaOH(aq) with CH 3 COOH(aq) NH 3 (aq) with Hcl(aq) 28. Which was most likely titrated to produce the curve below? CH 3 COOH(aq) H 2 CO 3 (aq) K 2 SO 3 (aq) Na 3 PO 4 (aq) 52.(a) Calculate the ph of a 0.15 mol/l solution of HCN(aq) if K a is 6.2 10 10. (b) (c) (d) (e) Determine the BrönsredLowry acidbase neutralization reaction that occurs when CH 3 COOH(aq) is added to Na 2 SO 3 (aq). Indicate which side of the reaction is favoured. A cup of herbal tea turns from red to pink when a slice of lemon is added to it. Drops of tea remaining in the cup turn purple as the cup is being washed with soapy water. What causes the colour changes observed? What is the ph of a solution formed by mixing 30.0 ml of 0.100 mol/l KOH with 70.0 ml of 0.200 mol/l HCl(aq)? Samples of hydrochloric acid, of unknown concentration, were titrated with a solution of sodium carbonate. The flasks were rinsed with a sodium carbonate stock solution before the samples of hydrochloric acid were added. Explain what effect this would have on the calculated concentration of acid. June 2007 13. Which is true of acids? feel slippery have a bitter taste react with metals to produce H 2 (g) turn red litmus paper blue 14. Which defines a modern Arrhenius acid? ionizes in water to produce H + ionizes in water to produce OH reacts with water to produce H 3 O + reacts with water to produce OH
15. In the reaction below, HCO3G(aq) is behaving as which type of substance? Arrhenius acid Arrhenius base BrinstedLowry acid BrinstedLowry base 16. Which is the conjugate acid and conjugate base of HPO 4 2? 17. Which 0.10 mol/l solution has the lowest [OH ]? F (aq) HCO 3 (aq) SO 2 3 (aq) SO 2 4 (aq) 18. Which describes the relationship between acid strength and Ka value? 19. Which best represents the BronstedLowry reaction between NaOH(aq) and HF(aq)? 20. What is the K w expression for the ionization of water? 21. What must occur to [H 3 O + ] in order to change the ph of a solution from 2.0 to 4.0? decrease by a factor of 2 decrease by a factor of 100 increase by a factor of 2 increase by a factor of 100 22. What is the ph of a solution with [H 3 O + (aq)] = 2.3 10 10 mol/l? 4.36 7.00 9.64 10.23 23. In the titration of an acid with a base, what substance is used for the final rinse of the pipette? acid base deionized water soap
24. Which graph illustrates the relationship between [H 3 O + (aq)] and [OH (aq)] in a solution? 25. Which substance is dibasic? 2 HPO 4 H 2 PO 4 HSO 4 H 2 SO 4 26. What does the expression below represent? 2 K a for H 2 P 2 O 7 K a for H 3 P 2 O 7 2 K b for H 2 P 2 O 7 K b for H 3 P 2 O 7 27. A 0.50 mol/l solution of an unknown acid has a ph of 1.4. Which graph shows the titration of this acid with 0.10 mol/l sodium hydroxide, NaOH?
28. Which indicator is best for the titration shown in the curve below? methyl orange orange IV thymol blue 1,3,5 trinitrobenzene 52.(a) A primary standard of Na 2 CO 3 (s) is used to determine the concentration of a hydrochloric acid solution. In the first trial a solution containing 0.5012 g of Na 2 CO 3 (s) required 21.35 ml of HCl(aq) to reach the equivalence point. (i) Based on this trial, what is the concentration of HCl(aq)? (ii) Why is it important to perform more than one trial? (b) What is happening at a molecular level, to explain why the ph of 1.0 mol/l CH 3 COOH(aq) is greater than the ph of 1.0 mol/l H 2 COOH(aq)? (c) Ethylamine is a weak base that ionizes according to the reaction below. Calculate the percent ionization of a 0.500 mol/l solution of ethylamine if its K b is 4.27 10 4. (d) The table below shows the results of tests performed on four 0.10 mol/l unknown solutions at 25 o C. Explain how this data can be used to identify which solution is NH 3 (aq), and which solution is NaOH(aq). June 2008 13. Which operationally defines an acidic acid solution? feels slippery ph is 8.0 tastes bitter turns litmus red 14. Which is considered an Arrhenius base? CH 3 OH CO2 HCN NaOH 15. According to BrinstedLowry theory, what is an acid? electron acceptor electron donor proton acceptor proton donor
16. Which is a BronstedLowry conjugate acidbase pair for the reaction below? HSO 3 (aq) and NH + 4 (aq) HSO 3 (aq) and SO 2 3 (aq) SO 2 3 (aq) and NH 3 (aq) SO 2 3 (aq) and NH + 4 (aq) 17. Which 0.100 mol/l acid solution has the lowest ph? HNO 2 (aq) H 2 CO 3 (aq) H 3 BO 3 (aq) H 3 PO 4 (aq) 18. Which represents the K w expression for water? 19. What is the poh for a 0.0150 mol/l hydrochloric acid solution? 0.0150 1.824 12.176 13.034 20. What is [H 3 O + ] of a 0.250 mol/l Ba(OH) 2 (aq) solution? 2.00 10 14 4.00 10 14 0.125 0.500 21. 100.0 ml of 0.625 mol/l HNO 3 (aq) is diluted with deionized water to a final volume of 150.0 ml. What is the ph of the resulting solution? 0.204 0.380 13.398 13.620 22. What does the expression below represent? 2 K a for CO 3 K a for HCO 3 2 K b for CO 3 K b for HCO 3 23. What is the ph of the equivalence point when NaOH(aq) is titrated with HCl(aq)? 1 7 10 14 24. During a titration experiment to determine the concentration of acetic acid, a student pipettes a sample of the acid into a flask contaminated with a weak base. What effect will this have on the experiment?
25. Which is the best definition for an acidbase indicator? strong acid strong base weak acid weak base 26. What is the ph range of a solution if orange IV indicator is yellow and methyl red indicator is red? 1.4 to 4.8 1.4 to 6.0 2.8 to 4.8 2.8 to 6.0 27. The titration curve below is for a 0.100 mol/l unknown acid titrated with sodium hydroxide. What is the unknown acid? HCl(aq) HCN(aq) H 2 SO 3 (aq) H 2 SO 4 (aq) 28. An unknown monoprotic acid with Ka = 3.2 10 9 is titrated with an unknown weak base. Which is the best indicator to determine the equivalence point? methyl red indigo carmine orange IV phenolphthalein 52.(a) Determine the BrinstedLowry acidbase neutralization reaction that occurs between NaHCO 3 (aq) and NH 4 NO 2 (aq). (b) Calculate the ph of a 0.297 mol/l solution of hypochlorous acid, HOCl(aq), which has K a = 2.9 10 8. (c) Using the data below, determine which solution is the best conductor of electricity, and explain why. (d) (e) Calculate the concentration and ph of a solution formed by mixing 25.00 ml of 0.125 mol/l HBr(aq), with 70.00 ml of 0.242 mol/l LiOH(aq). A person s breathing rate is slowed as a result of a stroke. With reference to the equations below, explain if the person is at risk for acidosis or alkalosis. June 2009 13. A sample of an unknown colourless liquid conducts electricity; however, the liquid does not react with Mg(s) to form small bubbles and it does not feel slippery. What is true of the liquid? acid amphoteric base ionic
14. Which represents the reaction of a Br nstedlowry base? NaOH(aq) W Na + (aq) + OH (aq) HNO 3 (aq) W H + (aq) + NO 3 (aq) CH 3 COOH(aq) + C 2 H 5 OH(l) W CH 3 COOCH 2 CH 3 (l) + H 2 O(l) H 2 C 2 O 4 (aq) + H 2 O(l) W H 3 O + (aq) + HC 2 O 4 (aq) 15. Which species is amphoteric? HNO 3 (aq) H 2 BO 3 (aq) H 3 BO 3 (aq) NO 3 (aq) 16. Which is the strongest acid? CH 3 COOH(aq) HF(aq) H 2 CO 3 (aq) H 2 SO 4 (aq) 17. In which acidbase equilibrium are the products favoured? HS (aq) + HCN(aq) W H 2 S(aq) + CN (aq) F (aq) + H 2 SO 3 (aq) W HSO 3 (aq) + HF(aq) NO 2 (aq) + HCN(aq) W HNO 2 (aq) + CN (aq) SO4 2 (aq) + HF(aq) W HSO 4 (aq) + F (aq) 18. Which species will react when solutions of HF and Na2CO3 are added together? HF(aq) and CO 2 3 (aq) HF(aq) and Na + (aq) H 3 O + (aq) and CO 2 3 (aq) H 3 O + (aq) and F (aq) 19. Which are the acids in the equilibrium below? H 2 BO 3 + H 2 PO 4 2 W H 3 BO 3 + HPO 4 2 HPO 4 and H 3 BO 3 H 2 BO 3 2 and HPO 4 H 2 BO 3 and H 2 PO 4 H 2 PO 4 and H 3 BO 3 20. What is true of a substance having a ph of 8? [H 3 O + ] is greater than [OH ] [H 3 O + ] is less than [OH ] [H 3 O + ] = [OH ] [H 3 O + ] = 0 21. Which theory states that an acid is a proton donor? Arrhenius BronstedLowry modified Arrhenius operational 22. What is the ph of a solution with [OH ] = 3.58 10 4? 3.446 3.580 10.420 10.554 23. In the equilibrium below, which is true if NaOH(aq) is added to the system? 2 HF(aq) + Ba(s) BaF2(aq) + H2(g) Equilibrium Shift ph left decrease left increase right decrease right increase 24. A 1.0 10 4 mol/l solution of KOH(aq) is diluted from 50.0 ml to 500.0 ml. What is the poh of the final solution? 3.00 5.00 9.00 11.00
25. A clear colourless solution has a ph of 1.1. What is the colour of the solution after thymol blue indicator is added to it? blue orange red yellow 26. Which is true at the equivalence point of a titration? acid concentration equals base concentration indicator changes colour moles of hydronium equals moles of hydroxide volume of acid equals volume of base 27. Which is necessary to perform a titration? burette crucible mass balance salt bridge 28. Which titration curve represents the addition of NaOH(aq) to HF(aq)? C) D) 29. Which describes an open system? matter and heat may be stationary matter and heat may be transferred only heat can flow in and out only matter can flow in and out 52.(a) Calculate the ph of a 0.25 mol/l solution of NH 3 (K b = 1.8 10!5 ). (b) Calculate the concentration of a 10.00 ml CH 3 COOH solution using the data provided from the standardization with a 0.1404 mol/l NaOH solution. Burette Trial 1 Trial 2 Trial 3 Final (ml) 16.90 32.02 47.18 Initial (ml) 1.35 16.90 32.02 Volume NaOH used (ml) 15.55 15.12 15.16 (c) (d) A solution is prepared by dissolving a 15.00 g sample of an alkali metal hydroxide, MOH(s), in enough water to make a 5.00 L solution. If the resulting ph is 12.466, identify the metal, M. A base is titrated with a strong acid to produce the graph below. Explain whether the base is strong or weak.