/20/2017 11:55 PM 2.9/3 3/12/2017 o3:s1 PM Grad Print Calculator Periodic Table
ID: 496578 • Letter: #
Question
/20/2017 11:55 PM 2.9/3 3/12/2017 o3:s1 PM Grad Print Calculator Periodic Table stion 6 of 10 Mapdet Sapling Learning A student must make a buffer solution with a pH of 1.0, Determine which of the acids and conjugate bases listed below are the best options to make a buffer at the specified pH. Weak acids: O formic acid, Ka 1.77x10 4,200 M O acetic acid, Ka 1.75x10 5, 5.00 M sodium bisultate monohydrate, Km 1.20x10 2,300 M O propionic acid, Ka 1.34x10 53.00 M Conjugate bases: O sodium sulfate decahydrate, Na2SO4. 10H2O O sodium propionate, CH3CHzCOONa sodium acetate trihydrate, CH O sodium formate, HCOONa down lo view more. The final volume of buffer solution must be 100,00 mL and the final concentration of the wenk acid must be 0.100 M Based on this information, what mass of solid on this information, what volume of conjugate base should the student weigh out to acid should the student measure O Previous check Answer ONext SExtExplanation / Answer
Ka of weak acid = 1.20 x 10^-2
pKa of weak acid = 1.92
pH = pKa + log [salt / acid]
1.0 = 1.92 + log [salt / acid]
[salt / acid] = 0.1202
acid moles = 100 x 0.1 / 1000
= 0.01
salt / acid = 0.1202
salt / 0.01 = 0.1202
salt (conjugate base) moles = 0.1202 x 0.01
= 1.202 x 10^-3
conjugate base molar mass =322.195 g/mol
mass = moles x molar mass
= 1.202 x 10^-3 x 322.195
= 0.387 g
mass of conjugate base = 0.387 g
total volume of buffer = 100 mL
volume of acid = x
volume of base = (100 - x )
millimoles of acid = 0.1 x
millimoles of base = (100 - x) 0.012
pH = pKa + log [salt / acid]
1.0 = 1.92 + log [(100 - x) 0.012 /0.1 x]
[(100 - x) 0.012 /0.1 x] = 0.1202
x = 50.0 mL
volume of acid = 50 mL
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