a The reaction shown below is Circle one reactant favored or product favored mL

A the reaction shown below is circle one reactant

This preview shows page 39 - 42 out of 84 pages.

a) The reaction shown below is (Circle one) reactant favored or product favored ? mL of 0.1 M NaOH added to reach the stoichiometric point in the titration of 100 mL of 0.2 M HF (aq) the actual pH at the stoichiometric point in the titration of 100 mL of 0.2 M HF (aq) with 0.1 M NaOH (aq) at 1/2 SP pH = pKa not at 1/2 SP pH < pKa more moles of acid, need more moles of base 0.01molF-/0.2L = 0.05M 0.02molF-/0.3L = 0.0667 more OH-; higher pH pH when 50 mL of 0.1 M NaOH (aq) has been added to 100 mL of 0.2 M HF (aq ) 8 2 pts for matching part b 2 pts multiply K when add 2 pts invert K 1 pt 1 pt K = 4.36x10 -5 >
Image of page 39
CHEM230 _W16 _PREP 3 _key p 40 288) Consider the three titrations labled A-C below: A) 10 mL of 0.1 M aqueous weak monoprotic acid (pK a = 6) titrated with 0.1 M NaOH (aq) B) 10 mL of 0.2 M aqueous strong monoprotic acid titrated with 0.1 M NaOH (aq) C) 10 mL of 0.1 M aqueous weak diprotic acid (pK a1 = 1.22; pK a2 = 4.21) titrated with 0.1 M NaOH (aq) i) Which of the three titrations will require the same volume of NaOH (aq) to reach their final stoichiometric point (SP): Write in the letter/s of ALL titrations that match the description. A B C A ii) Which of the three titrations will require the same volume of NaOH (aq) to reach their first stoichiometric point (SP): C iv) Which titration will have the highest pH at its final stoichiometric point? B iii) Which titration will have the highest pH at its first 1/2 stoichiometric point? A v) Which titration will have the lowest pH at its final stoichiometric point ? vi) At what volume of NaOH (aq) added will all three solutions have the same pH? (Circle one) 5 mL 10 mL 15 mL 20 mL 25 mL For a monoprotic acid, the first SP = the final SP 12 2each box
Image of page 40
CHEM230 _W16 _PREP 3 _key p 41 294a) Briefly explain the trend in the pK a s of the chlorobutanoic acid molecules shown above. The electronegative chlorine stabilizes the conj.base of butanoic acid, causing it to be a stronger acid (have a lower pK a ). As the chlorine atom moves further from the acidic proton, it is less effective at stabilizing the negative charge on the conj. base and the weaker the acid becomes (the larger its pK a ) 6 C O OH Cl 2-chlorobutanoic acid pK a = 2.86 C O OH 3-chlorobutanoic acid pK a = 4.0 Cl C O OH 4-chlorobutanoic acid pK a = 4.5 Cl An aqueous 0.1 M solution of each acid is prepared. Circle ONE answer in each box. b) Which chlorobutanoic acid has the largest van't Hoff i factor? 2-chloro 3-chloro 4-chloro all of the acids have the same i Each chlorobutanoic acid solution is titrated with 0.1 M NaOH (aq) . c) Which chlorobutanoic acid solution requires the largest volume of NaOH to reach its 1/2 stoichiometric point? 2-chloro 3-chloro 4-chloro all of the acids require the same volume d) Which chlorobutanoic acid solution has the highest pH at its 1/2 stoichiometric point? 2-chloro 3-chloro 4-chloro all of the acids have the same pH e) Which chlorobutanoic acid solution has the highest pH at its stoichiometric point?
Image of page 41
Image of page 42

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture