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Course Home Secure https://session.masteringchemistry.com cise 16 cise 16Secure https/ cise 16 stering /assignment/6358371 eringchemistry.com/myct/itemView?assignmentProblemiD-100832266 UNITS 20 22 HW For Practice 16.19 - Enhanced-with Feedback lf Assess nceptual You may want to reference (Pages 720-724) Section 16 10 whille completing this problem xercise 16 xercise 1 Part A or Practic FLd (CO,2 of a 0.030 M M carbonic acid solution Express your answer using two significant figures. xercise 1 Exercise 1 Exercise 16 cO,31 6.0 10 Exercise 16 Submit Conceptual incorrect: Try Again: 3 attempts remaining Back Provide Feedback 144 4S

Explanation / Answer

Explanation

[CO32-] = 7.38×10-8M

Explanation

First dissociation of H2CO3

H2CO3 <----> HCO3-  + H+

Ka1 = [HCO3-] [H+] /[H2CO3] = 4.5×10-7

  at equillibrium

[H2CO3] = 0.030 - x

[HCO3-] = x

[H+] = x

Therefore,

x2/(0.030- x) = 4.5×10-7

we can assume, 0.030- x~0.030 because x is small value

x2/0.030 = 4.5×10-7

x2 = 1.35×10-8

     x = 1.16×10-4

   [HCO3-] = 1.16×10-4M

second dissociation is

HCO3-   <------> H+ + CO32-

Ka2 = [ H+] [CO32-] /[HCO3-]

at equillibrium

[HCO3-] = 1.16×10-4 - x

[CO32-] = x

[H+] = x

therefore,

x2/(1.16×10-4 - x) = 4.7×10-11

we can assume, 1.16 ×10-4 - x ~1.16×10-4 because x is small value

x2/1.16×10-4 = 4.7×10-11

   x2 = 5.45×10-15

x = 7.38×10-8

[CO32-] = 7.38×10-8M

   

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