Exam 2 - Version 061 Exam 2 Laude (52455) 1 This print-out...

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 061 Exam 2 Laude (52455) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. K a = [ H + ] [ A- ] [ HA ] pK a =- log K a pH =- log [H + ] pOH =- log [OH- ] [ OH- ] = ( K b C b ) 1 / 2 [ OH- ] = K b parenleftbigg C b C a parenrightbigg 10- 14 = K w [H + ] [OH- ] = K w K a K b = K w pK a + pK b = pK w 14 = pK w ( K a C a ) 1 / 2 = [ H + ] K a parenleftbigg C a C b parenrightbigg = [ H + ] [ H + ] = ( K ax K ay ) 1 / 2 pH = 0 . 5( pK ax + pK ay ) 0 = [ H + ] 2- C a [ H + ]- K w K sp = [ C ] c [ A ] a 001 6.0 points The figure below shows the titration of a monoprotic weak acid with a strong base. b b I II Volume of base added pH The pH at point I is equal to the and the pH at point II is 7. 1. p K a of the acid; greater than correct 2. pH of the acid; greater than 3. pH of the acid; less than 4. p K a of the acid; less than 5. p K a of the acid; equal to Explanation: 002 6.0 points At the stoichiometric point in the titration of 0.130 M HCOOH(aq) with 0.130 M KOH(aq), 1. the pH is less than 7. 2. [HCOOH] = 0.0650 M. 3. the pH is greater than 7. correct 4. [HCO- 2 ] = 0.130 M. 5. the pH is 7.0. Explanation: 003 6.0 points A weakly acidic solution with a pH near 7 is formed when 1 10- 7 moles of H 2 SO 3 is added to 1 liter of water. How many equations must be solved in order to accurately calculate all of the unknown concentrations formed at equilibrium in solution? 1. 2 2. 3 3. 5 correct 4. 6 5. 4 6. 1 7. 7 Explanation: There are 5 ions that make contributions in this solution: H 2 SO 3 , HSO- 3 , SO 2- 3 , H + , and OH- . 004 6.0 points The weak acid equation [H + ] = ( K a C a ) 1 / 2 can be derived from [H + ] 3 + K a [H + ] 2- ( K w + K a C a )[H + ]- K a K w = 0 Version 061 Exam 2 Laude (52455) 2 if 1. K a is negligible and C a is significantly larger than [H + ]. 2. K values are far apart, K w is negligible and C a is significantly smaller than [H + ]. 3. K values are far apart, K w is negligi- ble and C a is significantly larger than [H + ]. correct 4. K w is negligible and C a is significantly smaller than [H + ]. 5. K w is negligible and C a is significantly larger than [H + ]. Explanation: 005 6.0 points If a solution of HOCl is titrated by a strong base such as NaOH, what is the pH at the half- neutralization point of the titration ( i.e., half- way to the equivalence point)? Note: You do not need to know the initial concentration of the acid. The ionization constant is 3 . 5 10- 8 for HOCl. 1. pH = 5.5 2. pH = 6.5 3. pH = 4.5 4. pH = 3.5 5. pH = 7.5 correct Explanation: K a = 3 . 5 10- 8 At half the equivalence point, this solution is a buffer in which [HOCl] = [OCl- ]....
View Full Document

This note was uploaded on 05/11/2010 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

Page1 / 7

Exam 2 - Version 061 Exam 2 Laude (52455) 1 This print-out...

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