5.1.9: Acid base magic trick
- Page ID
- 242457
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)CHEM 0103 Chemistry of the life sciences Group leader: Lab #9
Chemical calculator
Safety considerations and preparation
You are working with strong acids and bases today. Strong bases are dangerous when they get into your eyes. To protect yourself, wear splash goggles like you always to in the lab. If strong base gets into your eyes, you have to wash them in the eye wash for 15 minutes and seek medical care afterwards. The strong acid at the given concentration is less of a health concern (the concentration of HCl we are using is about the same as that in vomit); nevertheless, be cautious not to spill, and if you do, rinse affected body parts with water.
To prepare, transfer about 20 mL of 0.1M HCl (strong acid) from the hood into a beaker. In another beaker, put about 20 mL of 0.1 M NaOH plus one drop of phenolphthalein indicator. Bring the beakers to your bench.
Task 1: Magic trick
Repeat this magic trick to get everything (equipment, your brain) ready for designing a chemical calculator.
- Put approximately 50 mL of water into a 250 mL Erlenmeyer flask.
- Have the technician add a secret volume (4, 5, 6, 7 or 8 mL) of 0.1 M HCl (clear solution) with a syringe.
- Add 0.5 mL of 0.1 M NaOH (contains indicator, purple) for "good luck".
- Stepwise, add 1mL portions of 0.1 M NaOH (contains indicator, purplish-pink magenta) until the color appears and stays upon mixing. Did you figure out the secrete volume? Were you off by one mL?
Task 2: Chemical calculator
Design an experiment that takes a calculation (such as 4 + 5 or 8 – 3), translates the numbers into volumes and uses titration of a solution to figure out the answer (this seems silly, but pretend you can't add and substract and need a chemical calculator). In a typical experiment, you would mix different things in the beaker to set up the calculation, and then titrate with 1 mL portions of acid or base to read out the answer. For more drama, one person in the group can add one secret volume, and another another secret volume. This way, no one in the group has the complete information (i.e. knows the answer of the addition or subtraction problem until both reveal the volumes they used).
Task 3: Practice
You will have three practice questions for addition (2 + 4, 3 + 1, 2 + 2) and three for subtraction (4 - 2, 2 - 4, 6 - 3) to make sure your experiment works. Practice until you are comfortable with your method.
Task 4: Showtime
Perform your calculation in front of the class. Your “audience” will choose which calculation you will demonstrate (out of the three you practiced).