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Question

com/static/nb/ui/indexhtmi?mbld-708729&nbNodeld; 266530523&elSBN-9781305862883; 8xparentld 266530944 Use the Retereaces to access importast values if needed Sor this quenstion Determine the pH during the trati a of 250mL of0 250 M perchloric acid by 0.207 M barium hydroxide at the following por tx (1) Before the addition of any barium hydroxide (2) After the addation of 7.55 mL of barium hydroside (3) At the equivalence point 7 (4) After adding 18.9 ml of barium hydroxide n error has been delected in your answer Check or typos, eciclsions ec betore sumitting your Suemt Answer tration pHfs Strong Acid Srong Base. This is group attempt 1 of 10 Autosaved at 10 15 PM br bi

Explanation / Answer

1) Perchloric acid HClO4 is stronga cid and dissociates to complete extent H+ and ClO4-

before Ba(OH)2 added we have only HClO4 , [H+] = 0.25

pH = -log [H+] = -log ( 0.25)

= 0.6

2) HClO4 moles = 0.25 x 0.025 = 0.00625 = H+ moles

Ba(OH)2 moles = 0.207 x 0.00755 = 0.001563 mol

OH- moles = 2 x Ba(OH)2 = 2 x 0.001563 = 0.00313 mol

H+ moles after getting neutralised by OH- = 0.00625-0.00313 = 0.00312

volume of solution = 25+7.55 = 32.55 ml = 0.03255 L

[H+] = ( moles / volume) = ( 0.00312 / 0.03255) = 0.096

pH = -log ( 0.096)  

= 1.02

3) at equivalence H+ and OH- moles are equal , hence pH = 7

4) Ba(OH)2 moles = 0.207 x 0.0189 = 0.0039

OH- moles = 0.0039 x 2 = 0.0078

OH- moles left after ggeting neutralised to some extent by H+ = 0.0078-0.00625 = 0.00155

solution volume = 25+18.9 = 43.9 ml = 0.0439 L

[OH-] = ( 0.00155 mol / 0.0439) = 0.0353

pOH = -log ( 0.0353) = 1.45

pH = 14-1.45 = 12.55

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