122 QUIZ5wi06_recwk9 key

122 QUIZ5wi06_recwk9 key - so pD= - log (2.98 x 10-8 M) =...

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Name_____________________________________ Recitation TA__________________ 1 Recitation Week 9 P r o f . A l l e n Chapter 16 QUIZ V Chemistry 122 1. D 2 O (l) is deuterium oxide, or better known as “heavy water”. D 2 O (l) has an equilibrium constant, K D , of 8.90 x 10 -16 at 20.0 degrees C . Solve the following questions using the above information. Correct units and the number of significant figures are important to consider when reporting your answers (i.e. points are assigned to these). a) (4 points) Calculate [D + ] and [OD - ] for D 2 O at this temperature. X 2 = 8.90 x 10 -16 x = [D + ] = [OD - ] = 2.98 x 10 -8 M partial points: if the set up is correct, but a calculation error, +2 points: sig figs; should be 3 sig figs (worth 1 point); must have units in the answer (1 point) b) (3 points) What is the pD of this liquid? (Hint: pD is a pX function) pX = - log X
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Unformatted text preview: so pD= - log (2.98 x 10-8 M) = 7.526 if student used 2.983 x 10-8 M, then the answer would round to 7.525 partial points: if the set up is correct, but the # is a was incorrect and everything else was correct, give 3 points; 3 sig figs after the decimal place, so a total of 4 numbers in the answer (worth 1 point); If set up is correct, but a calculator error (+ 1 point) c) ( 3 points) What is the pK D of this liquid? pK D = - log K D = 15.051 partial points: 3 sig figs after the decimal place, so a total of 5 numbers in the answer (worth 1 point); If set up is correct, but a calculator error (+ 1 point) In lecture, students were informed that the number of decimal places in the log equals the number of significant figures in the pX function (see example 16.6 and appendix A)...
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