Study Guide for Chem 151 Lab Exam PDF

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Perfect Chem 151 Lab Exam for Dr. Enzenauer's lab class!...

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Study Guide for Chem 151 Lab Exam

VOCABULARY: Types of Errors: 1. Indeterminate Errors: a measurement is taken and reflect the inherent limitations of the instruments used (may lead to results that are too high, too low, or no effect on the final result) 2. True Value (actual value): the one measured most frequently 3. Propagation of Errors: results that are based on a series of measurements will be affected by the indeterminate error of each measurement 4. Determinate Errors: directional errors; affects the result in one direction (results are either too high or too low, not both) 

Gross Error: the incompetence of the experimenter; improper use of equipment, skipping a step in the lab procedure, spilling some of the samples before taking final measurements, and mathematical errors in calculations

5. Instrumental Errors: improper calibration of equipment 6. Method Error: inherent limitations of the procedure and experimental design (requires high level of critical thinking) 7. Precision: reflects the closeness of a given set of measurements to one another (how close two or more measurements are to each other) 8. Accuracy: reflects the closeness of a given measurement to the true value

Measuring Error:

1. Percent Error: expresses experimental error

2. Percent Difference: calculated the same as percent error; however, it compares an experimental result to a known absolute answer 3. Coefficient of determination (R2): expresses the linear regression of data points compared to their derived model 4. Significant Figure Conventions: a short-hand way to determine the degree of precision for a final result w/out going through all the necessary calculations to determine the exact amount of uncertainty

Other Vocab: 1. Covalent Compound: when two or more nonmetal atoms bond by sharing valence electrons 2. Ionic Compound: a chemical compound composed of ions held together by electrostatic forces 3. Qualitative Analysis: measures changes in color, melting point, odor, reactivity, boiling point, bubble production, and precipitation; tells “what” is in a sample 4. Quantitative Analysis: to tell “how much” is in a sample 5. Titration: a technique where a solution of known concentration is used to determine the concentration of an unknown solution 6. Analyte: can either be an acid or base, weak or strong 7. Standard solution: a solution containing an accurately known concentration of an element or a substance

8. Calorimetry: the process of measuring the amount of heat released or absorbed during a chemical reaction 9. Emission spectrum: the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state 10. Absorbance: a measure of quantity of light absorbed by a sample 11. Transmittance: the fraction of light that passes through the sample

REACTIONS: 1. Precipitation: a type of chemical reaction in which two soluble salts in aqueous solution combine and one of the products is an insoluble salt 2. Decomposition: which one reactant yield two or more products (ex. AB

A +B)

3. Oxidation-Reduction (redox): involves a transfer of electrons between two species 4. Acid-Base (neutralization reaction): consists of the transfer of a hydroxide ion (H+) from the acid to base

CALCULATIONS: Average: sum of the numbers in a given problem divided by the number of numbers added together Theoretical yield: 1. Determine number of moles of each reactant 2. Multiply the molecular weight by the number of moles in the equation 3. Multiply the ratio between the limiting reagent and the product by the number of moles of the limiting reagent used in the experiment 4. Multiply the number of moles of the product by the molecular weight of the product to determine the theoretical yield

Example:

Stoichiometry:

Dilution Use C1V1 = C2V2

Concentrations from calibration curves **answer is spectrometer (y=mx+b)

Enthalpy:

Or

Percent by mass:

Rydberg Equation:

R= 1.097 x 107 m-1 nl2 – low energy nh2 – high energy...