Exercise 17.39 Part A Use the Henderson-Hasselbalch equation to calculate the pl

Question

Exercise 17.39 Part A Use the Henderson-Hasselbalch equation to calculate the plI of each solution: a solution that is 0.125 M in HC1O and 0.180 M in KCIO Express your answer using two decimal places. pli7.70 Submit My Answers Give Up Correct Significant Figures Feedback: Your answer 7.69 was either rounded dlfferently or used a different number of significant figures than required for this part. Part B a solution that contains 1 .31% Og H5NH2 by mass and 1.18% C2H5 NH3 Br by mass Express your answer using two decimal places. pH = Submit MyAnswers Give Up Incorrect; Try Again; 5 attempts remaining Part C a solution that is 12.5 g of HC202 and 11.5 g of NaC23 Express your answer using two decimal places. n 150.0 mL of solution pH = Submit My Answers Give Up Continu

Explanation / Answer

B)

change to moles:

mass of C2H5NH2= 1.31

mass of C2H5NH3Br = 1.18

get moles

mol of C2H5NH2 = mass/MW = 1.31/45.0837 = 0.0290

mol of C2H5NH3Br = mass/MW = 1.18/125.9956=0.0093654

then

pOH = pKb + log(C2H5NH3+/C2H5NH2 )

pOH = 3.37 + log(0.0093654/0.0290) = 2.879

pH = 14-pOH = 14-2.879

pH = 11.121

C)

mol of acid = mass/MW = 12.5/60 = 0.208333

mol of acetate = mass/MW = 11.52/82 = 0.14048

pH = pKa + log(acetate/acid)

pH = 4.75 + log(0.1404/0.208333)

pH = 4.5786

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