122 QUIZ6wi06_ch17key

122 QUIZ6wi06_ch17key - Name Recitation TA Recitation Week...

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Name_____________________________________ Recitation TA__________________ 1 R e c i t a t i o n W e e k 1 0 P r o f . A l l e n Chapter 17 QUIZ VI Chemistry 122 1. Calculate the pH of a solution made by combining 125.0 mL of 0.050 M hydrofluoric acid with 50.0 mL of 0.10 M sodium fluoride. (The K a of hydrofluoric acid is 6.80 x 10 -4 .) Key: pH is 3.09 (or 3.07 assuming x is small or using HH eqn; see note below). 1 Point for correct sig figs (2 after the decimal place); if calculator error only (#s are written correctly; or a number transposed), give 8 points if everything else is perfect; some partial credit for correct approach, for example setting up the problem correctly with the correct conversions (no more than 5 points however). Note that there are 2 ways to do this problem. The most accurate being the ICE table set up shown in the first column (only the end results are shown) without assuming x is small, and the Henderson Hasselbalch approach. If one assumes x is small, the error is acceptable for this quiz. Therefore, assuming x is small as well as the Henderson Hasselbalch gets full credit if done
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