Overview
The lab exam covers all the experiments we have performed in the CHM 110 lab this semester. You will be allowed to use your lab notebook and your calculator for reference on the lab exam, but you are not allowed to use your textbook or lab manual. You will turn in your lab notebook for final evaluation when you turn in your lab exam, so do not forget your lab notebook!
To study for the lab exam, you should first read over your lab manual’s descriptions of the experiments and the notes that you took while performing each experiment. Perform some of the calculations you did during the labs. (In particular, calculations of concentration are very common in the CHM 110 labs.)
Experiments
Here is a list of the experiments you performed this semester:
| Number | Category | Summary |
|---|---|---|
| 1C | Measurements | Learning proper technique for mass measurements and volume measurements. Determining the precision of measurements using the standard deviation. |
| 1A | Qualitative analysis | Identify an unknown compound using a simple qualitative analysis scheme. |
| 3A | Empirical formulas | Determination of the empirical formula of magnesium oxide |
| 3B | Hydrates | Determining the products of the thermal decomposition of barium chloride dihydrate. |
| 4B | Ionic theory | Perform a series of exchange reactions (precipitations and neutralizations) and write chemical equations describing them. |
| 4C | Volumetric analysis | Determining the concentration of acetic acid in vinegar by titration. |
| 5B | Gas laws |
Determining the correct reaction for the decomposition of KClO3 by collecting the gas produced and determining the number of moles. |
| 6 | Calorimetry | Determining the heat of reaction for several reactions by calorimetry |
| 7 | Spectrometry | Determining the concentration of CoCl2 in an unknown by visible light spectrometry |
| 8 | Solubility | Investigating the solubility of alkaline earth (Group IIA) compounds in water |
Notes on the labs
- Measurements: You should be able to describe the proper use of the pipet and analytical balance. You should be able to use the density to convert from mass to volume or volume to mass. You should also be able to use the standard deviation to round an average to the correct number of significant figures.
- Qualitative analysis: You should be familiar with how these experiments work, and should have noted all the results of each individual test in your lab notebook.
- Empirical formulas: This lab required you to determine the empirical formula of magnesium oxide by burning magnesium and weighing the magnesium oxide produced. You should be able to describe how this experiment works and perform calculations similar to the ones you did in the experiment.
- Hydrates: This lab required you to thermally decompose a hydrate and, based on stoichiometry calculations, determine which of three decomposition reactions was the correct one. Be able to perform stoichiometry calculations (like the ones in chapter 3). Be able to describe the reactions of the colored hydrates.
- Ionic theory: You should also be able to write molecular and net ionic equations related to the precipitations and neutralizations you performed. Know how to operate a centrifuge, and be familiar with the safety hazards associated with any chemical used in these experiments.
- Volumetric analysis: This lab required you to determine the concentration of an unknown solution by titration – reacting the solution with a measured amount of a solution of known concentration. Be able to describe how titration is performed, and how phenolphthalein indicator reacts to acids and bases. You should also be able to perform the calculations from this lab using molarity units. See the molarity note pack on the web site and the end of chapter 4 in your textbook for help.
- Gas laws: This lab involved using concepts from previous labs (the stoichiometry calculations from the hydrates labs) along with the gas laws. You should be able to calculate the amount of product a reaction will produce given the amount of starting material – whether the product is solid or gaseous. You should also be able to find the moles of gas collected when the gas is collected over water. Collection over water means that some of the collected gas will actually be water vapor, and you must use Dalton’s law of partial pressures to subtract out the water vapor when finding out how many moles of gas were collected.
- Calorimetry: In this lab, you determined the heat of reaction for several reactions Be able to describe the use of a calorimeter, and be able to perform calculations involving heat capacity and specific heat.
- Spectrometry: This lab required you to determine the concentration of CoCl2 in an unknown by using Beer’s Law to construct a calibration curve relating the concentration of the CoCl2 to the absorbance of light at a wavelength of about 500 nm. Be able to define terms relating to Beer’s Law and describe the operation of a spectrometer. Be able to calculate the molar concentration (concentration in molarity units) of a solution made by dilution. You will find the molarity note pack from the course web site helpful when performing these calculations.
- Solubility: This lab required you to (qualitatively) determine the solubility of Group IIA metal compounds and compare them to each other and to lead(II). Be able to write the electron configuration for these metals (and others). Be able to describe the solubility trends for the Group IIA metal compounds you analyzed. Be able to write chemical formulas for the Group IIA and lead(II) compounds analyzed in the experiment.