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conve hman Coll ChemT Team: Hende -> c Dwww.saplinglearning.com/ibiscms/mod/ibis/view.php?id=2539723 A plugin (Shockwave Flash) isn't responding. Stop plugin 5/15/2016 1 1:55 PM O 7.5/10 5/15/2016 08:33 PM Assignment Information Available From: Not Set Due Date: Points Possible Grade Category: Graded Description: Policies: # Attempts Gradebook Print Calculator Periadic Table Question 6 of 8 Incorrect 5/15/2016 11:55 PM 10 What concentrations of acetic acid (pKa = 4.76) and acetate would be required to prepare a 0.20 M buffer solution at pH 4.9? Note that the concentration and/or pH value may differ from that in the first question STRATEGY 1. Rearrange the Henderson-Hasselbalch equation to solve for the ratio of base (acetate) to acid (acetic ractice 31 acid), [AVHA 2. Use the mole fraction of acetate to calculate the concentration of acetate 3. Calculate the concentration of acetic acid 2 Use the mole iraction of acetate to calculate the concentration of acetate You can check your answers. You can view solutions when you complete or up on any question. Step 1: Rearrange the Henderson Hasselbalch equation to solve for HA The Henderson-Hasselbalch equation is You can keep trying to answer each question you get it right or give up loading modules pH-pK+ log HA There is no penalty for incorrect answers. Use the Henderson-Hasselbalch equation to solve for if the solution is at pH 4.9 HA eTextbook Number Enter your answer as a number. For example, 9.6 Do not enter a formula like 106+2 HA 0.96 D Help With This Topic Web Help & Videos Technical Support and Bug Reports Previous Give Up & View Solution # Try Again Next Exit Explanation 9:58 PM / GO) d 5/15/2016 Search the web and Windows

Explanation / Answer

Ph = Pka + log(acetae/acetic acid)

given Ph = 4.9 , Pka = 4.76

now

4.9 = 4.76 + log(acetae/acetic acid)

[A-]/[HA] = 0.14

let us conside [A-] = x, [HA] = y

[A-] = 0.14*[HA]

x = 0.14y

molefraction of [A-] = no.of moles of [A-]/total no. of moles

                              = x/[x+y]

                             = 0.14y/[0.14y + y]

                            = 0.14y/1.14y

molefraction of acetate   = 0.123

we know that

molefraction of acetate + molefraction of acetic acid = 1

mole fraction of acetic acid = 1-0.123 = 0.877

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