MgO Calorimetry
- Page ID
- 202751
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Week 1: Calibrating Calorimeter
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HCl(aq) and NaOH(aq) are provided for you, with the concentrations labeled. Be sure to record these concentrations.
Keep the NaOH(aq) covered with a watch glass to avoid carbon dioxide gas from dissolving and changing the concentration. Note that CO(g) dissolves as carbonic acid.
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Pour the required amount of HCl (aq) into a styrofoam cup labeled HCl. This will hold the HCl (aq) at constant temperature. The NaOH can be transferred into the Calorimeter cup (not shown). While these solutions come to a steady temperature, you can set-up your MicroLab.
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 IMAGE: University of Liver Pool chemistry structure pages (ChemTube3D) |
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Setting up the MicroLab can be done just like was done for the 1 - Intro to Calorimetry experiment, with one exception: set the data collection interval in the bottom left corner to 2.0 seconds instead of the default 0.5 seconds. This is accomplished by double-clicking the text "Repeat every 0.5 seconds" in the lower-left corner. |
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Once you are ready, place the HCl cup in place and measure the temperature for at least 20-30 seconds (10-15 data points). DO NOT PRESS STOP ON THE MICROLAB.
Simply raise the thermister and replace the HCl (aq) with the calorimeter containing NaOH (aq).
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When initially taking the temperature of the NaOH(aq), do not add the stir bar |
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This is the set-up of the calorimeter with the lid in place. The thermister should have a black mark on it indicating where to place it.
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Do not lower the thermister below this point or you could puncture the styrofoam cup bottom. Record the temperature of the NaOH (aq) for at least 20-30 seconds (10-15 data points). Again, DO NOT PRESS STOP ON THE MICROLAB.
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To add the HCl (aq) and the stir bar to the NaOH (aq), raise the lid of the calorimeter without moving the thermister. The stir bar should be stirring vigorously enough to create a small vortex on the surface of the liquid, but not so vigorously that you see bubbles.
NaOH (aq) + HCl (aq) → H2O (l) + NaCl (aq) Continue taking data for an additional 5 minutes (an additional 300 seconds, or 150 data points). Record the time at which you dumped the HCl (aq) into the NaOH (aq).
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The data collected will have some jumps when you removed the thermister from the HCl (aq). You should see flat lines before the initial dip, after the dip, and then a slowly descending line after the reaction occurs.
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Week 2: MgO Calorimetry
In this week, you will be reacting a solid with a liquid. It is important that the total volume of solution in the coffee-cup calorimeter is consistent with last week's calibration and that you are using the same calorimeter with lid you used last week. The total volume of 1M HCl (aq) used for all trials this week will be 75 mL from the pump dispenser (3x25mL pumps). This can be dispensed straight into a clean, dry calorimeter.
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The mass of the solid reagent used will determined indirectly by weighing a vial both before you add the reagent and then again after adding.
First weigh the full vial and record the mass. The mass shown here is 9.1408 g MgO (s).
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IMAGE: C. B. Walker and M. Marezio, Acta Met., 1959, 7, 769.
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Record the time that you dump the vial of reagent into the calorimeter. It is not very important that you get all of the reagent into the calorimeter. Any residue left in the vial will be accounted for by weighing the vial afterward. Ensure that the powder is poured directly into the center of the calorimeter solution surface to avoid sticking to the edges and make sure that the powder does not clump up in the solution.
MgO (s)+2 HCl (aq) → MgCl2 (aq)+H2O (l) |
Image: http://ww2.chemistry.gatech.edu/  |
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To determine how much reagent was added to the solution, weigh the vial again. The mass shown below is 8.5442 g.
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