Exercise 14.56 with eText link MasteringChemistry 10 of 16 Exercise 14.56 with e

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Exercise 14.56 with eText link MasteringChemistry 10 of 16 Exercise 14.56 with eText link Determine [H3O+] in each acid solution. If the acid is weak, indicate the value that [H3O+] is less than. Part A 0.125 M HClO2 0.125 [H3O+]=0.125 M [H3O+]<0.250 M [H3O+]=0.0625 M [H3O+]<0.125 M SubmitGive Up Part B 1.25 M H3PO4 1.25 [H3O+]<3.75 M [H3O+]<1.25 M [H3O+]=3.75 M [H3O+]=1.25 M SubmitGive Up Part C 2.77 M HCl 2.77 [H3O+]=5.54 M [H3O+]<2.77 M [H3O+]=2.77 M [H3O+]<5.54 M SubmitGive Up Part D 0.95 M H2SO3 0.95 [H3O+]<1.90 M [H3O+]<0.95 M [H3O+]=1.90 M [H3O+]=0.95 M SubmitGive Up Continue

Exercise 14.56 with eText link MasteringChemistry 10 of 16 Exercise 14.56 with eText link Determine [H3O+] in each acid solution. If the acid is weak, indicate the value that [H3O+] is less than. Part A 0.125 M HClO2 0.125 [H3O+]=0.125 M [H3O+]<0.250 M [H3O+]=0.0625 M [H3O+]<0.125 M SubmitGive Up Part B 1.25 M H3PO4 1.25 [H3O+]<3.75 M [H3O+]<1.25 M [H3O+]=3.75 M [H3O+]=1.25 M SubmitGive Up Part C 2.77 M HCl 2.77 [H3O+]=5.54 M [H3O+]<2.77 M [H3O+]=2.77 M [H3O+]<5.54 M SubmitGive Up Part D 0.95 M H2SO3 0.95 [H3O+]<1.90 M [H3O+]<0.95 M [H3O+]=1.90 M [H3O+]=0.95 M SubmitGive Up Continue

Exercise 14.56 with eText link MasteringChemistry 10 of 16 Exercise 14.56 with eText link Determine [H3O+] in each acid solution. If the acid is weak, indicate the value that [H3O+] is less than. Part A 0.125 M HClO2 0.125 [H3O+]=0.125 M [H3O+]<0.250 M [H3O+]=0.0625 M [H3O+]<0.125 M SubmitGive Up Part B 1.25 M H3PO4 1.25 [H3O+]<3.75 M [H3O+]<1.25 M [H3O+]=3.75 M [H3O+]=1.25 M SubmitGive Up Part C 2.77 M HCl 2.77 [H3O+]=5.54 M [H3O+]<2.77 M [H3O+]=2.77 M [H3O+]<5.54 M SubmitGive Up Part D 0.95 M H2SO3 0.95 [H3O+]<1.90 M [H3O+]<0.95 M [H3O+]=1.90 M [H3O+]=0.95 M SubmitGive Up Continue

Explanation / Answer

Part A. 0.125 M HClO2, is a moderately strong acid, and dissociation constant Ka = 1.1×10–2
       HClO2 + H2O ---------.>H3O+ + ClO2-

   at equlibirium concentrations of [H3O+] = X, [ClO2-] = X, [HClO2] = 0.125-X

                Ka = [H3O+] [ClO2-]/ [HClO2]

              1.1 x 10-2 = [X] [X] / [0.125 -X]
       1.1 x 10-2 [0.125 -X] = X2
               0.001375 - 0.011 X = X2
       X2 + 0.011X - 0.001375 =0
        using the quadratic equation at
   X = 0.032 M
            it is [H3O+]<0.0625 m

Part B. 1.25 M H3PO4 is moderate acid whose Ka's show it in quite weaker. In a solution that has only water   and phosphoric acid there are four possible sources of hydrogen ion, the water and the three ionizations of the phosphoric acid. Each ionization has a different Ka.
    Ka1 =7.1×10–3 , Ka2 = 6.3×10–8, Ka3 = 4.2×10–13

    expect it to be [H3O+]<1.25 M

Part C. 2.77 M HCI, is a very strong acid

      HCl -------- H+ + Cl-

      [H+] = [HCl] = 2.77M
         [H+]= [H3O+]=2.77 M

Part D. 0.95 M H2SO3 , is not much different than HClO2 in strength, its Ka's are
            Ka1 = 1.3×10–2 (only the 1st H+ releases to any great concern)
             Ka2 = 6.2×10–8 (so weak it doesn't even matter )

            [H3O+]<0.95

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