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Chap15Test

# Chap15Test - Chapter 15 Practice Test(Answers start on page...

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Chapter 15 Practice Test (Answers start on page 27) 1. What combination of substances will give a buffered solution that has a pH of 5.05? (Assume each pair of substances is dissolved in 5.0 L of water.) ( K b for NH 3 = 1.8 ¥ 10 - 5 ; K b for C 5 H 5 N = 1.7 ¥ 10 - 9 ) [A] 1.0 mole C 5 H 5 N and 1.5 mole C 5 H 5 NHCl [B] 1.0 mole NH 3 and 1.5 mole NH 4 Cl [C] 1.5 mole NH 3 and 1.0 mole NH 4 Cl [D] 1.5 mole C 5 H 5 N and 1.0 mole C 5 H 5 NHCl [E] none of these 2. You have solutions of 0.200 M HNO 2 and 0.200 M KNO 2 ( K a for HNO 2 = 4.00 ¥ 10 - 4 ). A buffer of pH 3.000 is needed. What volumes of HNO 2 and KNO 2 are required to make 1 liter of buffered solution? [A] 413 mL HNO 2 ; 587 mL KNO 2 [B] 714 mL HNO 2 ; 286 mL KNO 2 [C] 500 mL of each [D] 286 mL HNO 2 ; 714 mL KNO 2 [E] 587 mL HNO 2 ; 413 mL KNO 2 3. 15.0 mL of 0.50 M HCl is added to a 100.-mL sample of 0.200 M HNO 2 ( K a for HNO 2 = 4.0 ¥ 10 - 14 ). What is the equilibrium concentration of NO 2 - ions? [A] 1.1 ¥ 10 - 13 M [B] 6.5 ¥ 10 - 12 M [C] 7.5 ¥ 10 - 14 M [D] 1.7 ¥ 10 - 11 M [E] none of these 4. A solution contains 0.250 M HA ( K a = 1.0 ¥ 10 - 6 ) and 0.45 M NaA. What is the pH after 0.10 mole of HCl is added to 1.00 L of this solution? [A] 10.83 [B] 10.77 [C] 6.00 [D] 3.23 [E] 3.17 5. A weak acid, HF, is in solution with dissolved sodium fluoride, NaF. If HCl is added, which ion will react with the extra hydrogen ions from the HCl to keep the pH from changing? [A] F - [B] Na + [C] Na - [D] OH - [E] none of these 6. Which of the following is true for a buffered solution? [A] The solution resists change in its [H + ]. [B] The solution will not change its pH very much even if a concentrated acid is added. [C] Any H + ions will react with a conjugate base of a weak acid already in solution. [D] The solution will not change its pH very much even if a strong base is added. [E] all of these

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The following questions refer to the following system: A 1.0-liter solution contains 0.25 M HF and 0.60 M NaF ( K a for HF is 7.2 ¥ 10 - 4 ) 7. What is the pH of this solution? [A] 0.94 [B] 2.8 [C] 3.5 [D] 4.6 [E] 1.4 8. If one adds 0.30 liters of 0.020 M KOH to the solution what will be the change in pH? [A] 0.4 [B] 0.2 [C] 0.0 [D] 0.5 [E] none of these 9. Calculate the [H + ] in a solution that is 0.10 M in NaF and 0.20 in HF. ( K a = 7.2 ¥ 10 - 4 ) [A] 7.0 ¥ 10 - 4 M [B] 0.20 M [C] 3.5 ¥ 10 - 4 M [D] 1.4 ¥ 10 - 3 M [E] none of these 10. Which of the following will not produce a buffered solution? [A] 100 mL of 0.1 M Na 2 CO 3 and 50 mL of 0.1 M HCl [B] 100 mL of 0.1 M Na 2 CO 3 and 50 mL of 0.1 M NaOH [C] 50 mL of 0.2 M Na 2 CO 3 and 5 mL of 1.0 M HCl [D] 100 mL of 0.1 M Na 2 CO 3 and 75 mL of 0.2 M HCl [E] 100 mL of 0.1 M NaHCO 3 and 25 mL of 0.2 M HCl 11. How many moles of HCl need to be added to 150.0 mL of 0.50M NaZ to have a solution with a pH of 6.50? ( K a of HZ is 2.3 ¥ 10 - 5 ). Assume negligible volume of the HCl. [A] 1.0 ¥ 10 - 3 [B] 7.5 ¥ 10 - 2 [C] 6.8 ¥ 10 - 3 [D] 5.0 ¥ 10 - 1 [E] none of these 12. Calculate the pH of a solution that is 0.5 M in HF ( K a = 7.2 ¥ 10 - 4 ) and 0.6 M in NaF. [A] 5.53 [B] 1.72 [C] 3.32 [D] 3.44 [E] 8.46
13. Consider a solution consisting of the following two buffer systems: H 2 CO 3 HCO 3 - + H + p K a = 6.4 H 2 PO 4 - HPO 4 2 - + H + p K a = 7.2 At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present?

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Chap15Test - Chapter 15 Practice Test(Answers start on page...

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