2.1: Pre-lab assignment
- Page ID
- 401633
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)In this module, you'll develop a crucial skill: the accurate use of volumetric pipettes and volumetric flasks for solution preparation. To get ready, read all of the contents of Module 2 and watch the videos below to learn how to use the volumetric glassware correctly.
Pre-Lab Assignment
- Read the contents of this module
- Download the example calibration template (Excel document), open it, and examine its contents (it is linked within the reading assignment in this module and copied here for convenience: Link for Duke Students).
- Write the following in your notebook before the start of lab. Your instructors will check your notebook at the start of the lab period.
- Draw the structure of bromocresol green in its basic and acidic forms. Which is the form you will measure, and what is the wavelength used to monitor its concentration?
- Sketch a predicted plot of absorbance (at the specific wavelength) vs concentration of bromocresol green. Label the data points for solutions B-F on your sketch.
- Create a table in your notebook where you will record absorbance readings.
- You will record three absorbance readings for each CALIBRATION SOLUTION F through B.
Note: you will measure them in the order of increasing concentration (alphabetically backward), in the order F, E, D, C, B, so you may want to put them in this order in your table. - Include a place to record the average and the standard deviation of the three readings for each calibration solution.
- Include a place to record readings for the VALIDATION STANDARD (aka "control" solution) and the SAMPLE (aka "unknown solution").
- You will record three absorbance readings for each CALIBRATION SOLUTION F through B.
- Calculate the expected molarity of bromocresol green in each diluted solution. (Remember: \(M_1V_1=M_2V_2\).) Also calculate the error associated with each solution's concentration using propagation of error.
(Hint: you'll need to calculate the error in the original stock solution first. Then calculate the error for each diluted solution using the precision of the volumetric glassware.)
You should complete the above tasks prior to the start of your laboratory period.
Instructions
Watch the following videos. The first two videos explain the correct use of volumetric pipettes and bulbs. The third video explains the correct use of volumetric flasks. And the fourth explains how to use automatic pipettes.
| How to use Volumetric Pipettes and pipette bulbs | |
| How to use volumetric flasks | |
| How to use an automatic pipette (aka "pipetter" or "pipetteman" | |
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