CH302 Exam 3-solutions

CH302 Exam 3-solutions - Version 054 Exam 3 sutcliffe...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Version 054 Exam 3 sutcliffe (51630) 1 This print-out should have 28 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Which of the following mixtures would pro- duce a buffer? I) 100 mL of 0.1 M NH 4 Cl + 75 mL of 0.1 M NaOH II) 100 mL of 0.1 M NH 3 + 100 mL of 0.5 M HCl III) 100 mL of 0.1 M NaCl + 50 mL of 0.2 M HCl IV) 100 mL of 0.1 M HClO 2 + 100 mL of 0.1 M NaClO 2 V) 100 mL of 0.1 M NH 3 + 75 mL of 0.1 M NaOH 1. I, IV, and V only 2. II and III only 3. I and IV only correct 4. I only 5. I, II, III, and IV only Explanation: A bu ff er contains a weak acid or weak base, plus the salt of that weak acid or base; or, a mixture which will have this composition after any acid-base reactions occur. You may have to calculate the number of moles of each species to determine the composition after any acid-base reaction. 002 10.0 points What volume of 0.602 M Sr(OH) 2 would be needed to neutralize 13.2 L of 3.01 M H 2 SO 4 ? 1. 66.0 L correct 2. 132 L 3. 39.7 L 4. 23.9 L 5. 33.0 L Explanation: [Sr(OH) 2 ] = 0.602 M V H 2 SO 4 = 13.2 L [H 2 SO 4 ] = 3.01 M The balanced equation for the reaction is Sr(OH) 2 + H 2 SO 4 SrSO 4 + 2 H 2 O V Sr(OH) 2 = 13 . 2 L H 2 SO 4 3 . 01 mol H 2 SO 4 1 L H 2 SO 4 soln 1 mol Sr(OH) 2 1 mol H 2 SO 4 1 L Sr(OH) 2 soln . 602 mol Sr(OH) 2 = 66 . 0 L 003 10.0 points Adding NH 4 NO 2 to pure water would result in what kind of solution? K a for HNO 2 is 4 . 5 10- 4 and K b for NH 3 is 1 . 8 10- 5 . 1. basic 2. acidic correct 3. neutral Explanation: 004 10.0 points A solution is prepared by mixing equal vol- umes of 0.40 M HF(aq) with 0.40 M KOH(aq). This solution is a buffer. 1. False correct 2. True Explanation: 005 10.0 points What is the pH of an aqueous solution that is 1.0 M HClO ( K a = 3 . 10- 8 ) and 0.75 M NaClO? 1. 7.40 correct Version 054 Exam 3 sutcliffe (51630) 2 2. 7.52 3. 7.64 4. 6.36 5. 6.60 Explanation: 006 10.0 points We want the value of X divided by Y where X is the hydrogenphosphate ion concentra- tion and Y is the dihydrogenphosphate ion concentration. Calculate the ratio of the molarities of HPO 2- 4 and H 2 PO- 4 ions required to achieve buffering at pH = 7.00. For H 3 PO 4 , p K a1 = 2.12, p K a2 = 7.21, and p K a3 = 12.68. 1. 1.23 2. 0.81 3. 0.21 4. 0.62 correct 5. 1.62 Explanation: 007 10.0 points Consider mixing HNO 3 and NaNO 3 . This is NOT a buffer because 1. Na reacts with water to form OH- . 2. NaNO 3 is not soluble. 3. NO- 3 reacts with water to form NO 2 (g). 4. NaNO 3 is basic. 5. HNO 3 is not a weak acid. correct Explanation: 008 10.0 points A bu ff er is formed by mixing 100 mL of 0.2 M HClO 2 and 200 mL of 0.7 M KClO 2 . What volume of 0.2 M KOH can be added before the buffer capacity is reached?...
View Full Document

Page1 / 8

CH302 Exam 3-solutions - Version 054 Exam 3 sutcliffe...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online