Chem2100 Final Exam Study Guide Flashcards

Chem 2100 - Final Exam Study Guide

1. Qualitative vs Quantitative Analysis

• Qualitative Analysis: Involves determining the presence or absence of a substance in a sample.

• Quantitative Analysis: Involves determining the amount or concentration of a substance in a sample.

2. General Steps in Chemical Analysis

• Step 1: Sample Collection

• Step 2: Sample Preparation

• Step 3: Analysis

• Step 4: Interpretation of Results

3. Homogenous and Heterogeneous Samples

• Homogeneous Samples: Uniform composition throughout; individual components are not visible (e.g., saltwater).

• Heterogeneous Samples: Composition varies; individual components can be seen (e.g., sand and salt mixture).

4. Definitions of Key Terms

• Decant: The process of pouring off a liquid without disturbing the sediment.

• Filtrate: The liquid that has passed through a filter.

• Supernatant: The liquid layer that lies above a sediment after decanting or centrifuging.

• Mother Liquor: The liquid that remains after crystallization from a solution.

• Precipitate: A solid that forms and settles out of a liquid mixture.

5. Sample Preparation Process

• Involves the steps to properly collect, store, and handle samples prior to analysis to avoid contamination or degradation.

6. Calibration Curve

• A graph used to determine the concentration of an unknown sample based on the known concentrations of standard solutions.

7. Masking

• The process of adding a reagent to selectively inhibit the reactivity of certain ions while allowing others to react in a chemical analysis.

8. Lot, Bulk Sample, and Aliquot

• Lot: A batch of material produced under similar conditions.

• Bulk Sample: A large quantity of material that represents the entire material in a specific environment.

• Aliquot: A measured sub-volume of a larger sample used for analysis.

9. Effect of Sample Storage on Analysis

• Improper storage can lead to degradation, contamination, or changes in concentration of analytes, affecting the accuracy of analytical results.

10. Essential Formulae and Unit Conversions

• Know fundamental equations used in chemical analysis and conversions between various units including SI units.

11. Calculations in Chemistry

• Molar Mass: Sum of the atomic weights of all atoms in a molecule.

• Moles: Quantity equal to the amount of substance that contains as many entities as there are atoms in 12 grams of carbon-12.

• Molarity (M): Concentration of a solution expressed in moles of solute per liter of solution ($M = rac{n}{V}$).

• Molality (m): Concentration expressed in moles of solute per kilogram of solvent ($m = rac{n}{mass_{solvent}}$).

• Formal Concentration: Number of moles of solute divided by volume of solution.

• Percent Composition: Mass percentage of a component in a mixture.

• ppm: Parts per million - concentration measurement.

• ppb: Parts per billion - used for very low concentrations.

12. Dilution Formula

• Formula used: $M<em>iV</em>i = M<em>fV</em>f$, where $Mi$ and $Vi$ are initial concentration and volume, and $Mf$ and $Vf$ are final concentration and volume.

13. Solution, Solute, Solvent

• Solution: A homogeneous mixture of two or more substances.

• Solute: Substance dissolved in a solution.

• Solvent: The substance in which the solute is dissolved, typically present in a greater amount.

14. Gravimetric Analysis

• A method of quantitative analysis based on measuring the mass of a substance; often involves the precipitation of an analyte to determine its mass.

15. Safe and Ethical Handling of Chemicals and Waste

• Adherence to guidelines for safe handling of hazardous materials and proper disposal of chemical waste to mitigate environmental impact.

16. Buoyancy

• The ability of an object to float in a fluid; due to the upward force exerted by the fluid.

17. Random vs Systematic Error

• Random Error: Errors that occur unpredictably and are not reproducible.

• Systematic Error: Errors that occur consistently in the same direction; can often be identified and corrected.

18. Gaussian Distribution

• A common probability distribution that is symmetric about the mean, depicting how values are distributed in a dataset.

19. Sample Mean and Standard Deviation

• Mean: The average value calculated by summing all data points and dividing by the number of points.

• Standard Deviation ($ext{SD}$): A measure of the amount of variation or dispersion in a set of values. Formula: ext{SD} =
  m igg( rac{1}{N-1} ext{∑}i (xi - ar{x})^2igg)^{1/2}

20. Confidence Interval

• A range of values derived from sample statistics that is likely to contain the true population parameter with a specified probability (e.g., 95% confidence).

21. Types of Blanks

• Method Blank: Contains reagents and solvents but no analyte; used to account for background noise in measurements.

• Field Blank: Taken to the site of sample collection and exposed to the same environment, used to assess contamination.

22. Quality Assurance vs Quality Control

• Quality Assurance (QA): Procedures to ensure the quality of the analysis process and methods used.

• Quality Control (QC): The operational techniques and activities used to fulfill requirements for quality; includes monitoring analytical results.

• Spike: A known quantity of analyte added to a sample to assess the recovery of the analysis method.

• Percent Recovery: A measure of the accuracy of an analytical method, calculated as: $Percent ext{ } Recovery = rac{(amount ext{ }found - amount ext{ }original)}{amount ext{ }added} imes 100$

23. Method Validation and Standard Addition

• Method Validation: Process of demonstrating that an analytical method is reliable for a specific purpose.

• Standard Addition: A technique used to quantify an unknown by adding known quantities of a standard to the sample.

24. Titration Curves

• Strong Acid vs Strong Base: Rapid change in pH around the equivalence point, creating a steep slope.

• Strong Acid vs Weak Base: Curve gradually rises, has a lower pH at equivalence point.

• Weak Acid vs Strong Base: Similar gradual rise, higher pH at equivalence point.

• Polyprotic Systems: Titration of acids with more than one dissociable proton, resulting in multiple equivalence points.

25. Buffer Solutions

• A solution that resists changes in pH upon addition of small amounts of acid or base.

• Henderson-Hasselbalch Equation: Used to calculate the pH of buffer solutions: pH = pK_a + ext{log}igg( rac{[A^-]}{[HA]}igg), where $[A^-]$ is the concentration of the conjugate base and $[HA]$ is the concentration of the acid.

26. Buffer Capacity

• The ability of a buffer solution to resist changes in pH; higher concentrations of the acid-base pair increase buffer capacity.

27. Equivalence Point

• The point in a titration where the amount of titrant added is chemically equivalent to the amount of substance being titrated.

28. Purpose of Gran Plot

• A graphical method to determine concentration of unknown solutions by plotting appropriate variables to find the equivalence point.

29. Indicator and Indicator Error

• Indicator: A chemical substance that changes color at a certain pH level thereby signaling the endpoint of a titration.

• Indicator Error: The discrepancy between the actual equivalence point and the endpoint indicated by the color change of the indicator.

30. Kjeldahl Nitrogen Analysis

• A quantitative method to determine nitrogen content in organic compounds through conversion to ammonium sulfate followed by titration.

31. Leveling Effect

• A phenomenon in which strong acids and bases react with water to produce only hydronium and hydroxide ions, not existing in their original forms in solution.

32. EDTA

• EDTA (Ethylenediaminetetraacetic acid): A chelating agent with the ability to bind metal ions, used in analytical chemistry for titrations.

33. Dentate Definitions

• Monodentate: Ligands that form one bond to a metal ion.

• Bidentate: Ligands that form two bonds to a metal ion.

• Multidentate: Ligands that form more than two bonds to a metal ion.

34. Chelate Effect

• The increased stability of a complex formed between a metal ion and a multidentate ligand compared to the corresponding complex formed with monodentate ligands.

35. Formation Constant and Conditional Formation Constant

• Formation Constant ($K_f$): Equilibrium constant for the formation of a complex ion from its components. Found using data from tables such as Table 12-1 and 12-2 of the textbook.

• Conditional Formation Constant: Takes into account other equilibria influencing the concentration of reactants or products in the formation of a complex.

36. EDTA Titration Curves and Calculating $pM$

• Understand the different regions of titration curves before, at, and after the equivalence point; demonstrate the calculations for molality and concentration.

37. Equilibrium Constant of a Reaction

• The ratio of the concentrations of products to reactants at equilibrium, expressed as $K = rac{[products]}{[reactants]}$.

38. Enthalpy, Entropy, and Gibbs Free Energy

• Enthalpy (H): A measure of the heat energy in a system.

• Entropy (S): A measure of disorder in a system.

• Gibbs Free Energy (G): Determines the spontaneity of a reaction: $G = H - TS$ (where T is temperature in Kelvin).

39. Le Châtelier’s Principle

• A principle stating that if an external change is applied to a system at equilibrium, the system will adjust to counteract the change and restore a new equilibrium.

40. Solubility Product (Ksp)

• The equilibrium constant for the dissolution of a sparingly soluble salt; expressed as: $K_{sp} = [A^+]^m[B^-]^n$, where A and B are the ions produced by the dissolution.

41. Saturated Solution

• A solution in which no more solute can dissolve at a given temperature, resulting in dynamic equilibrium between dissolved and undissolved solute.

42. Common Ion Effect

• The reduction in solubility of a salt when a common ion is added to a solution that already contains that ion.

43. Brønsted-Lowry Acids and Bases

• Brønsted-Lowry Acid: Donates a proton (H⁺).

• Brønsted-Lowry Base: Accepts a proton (H⁺).

44. Autoprotolysis of Water

• The reversible reaction of water in which a molecule of water donates a proton to another water molecule: $2H<em>2O ightleftharpoons H</em>3O^+ + OH^-$.

45. Calculating pH and pOH

• $pH = - ext{log}[H_3O^+]$

• $pOH = - ext{log}[OH^-]$

• Relation: $pH + pOH = 14$ for aqueous solutions at 25°C.

46. Common Strong Acids/Bases

• Strong Acids: HCl, HNO₃, H₂SO₄.

• Strong Bases: NaOH, KOH, Ca(OH)₂.

47. Ionic Atmosphere

• Refers to the distribution of ions in a solution that affects the solubility and behavior of salts due to electrostatic interactions.

48. Calculating Ionic Strength

• Ionic strength ($ext{I}$) is calculated as: $ext{I} = rac{1}{2} ext{∑} c<em>i z</em>i^2$, where $c<em>i$ is the concentration and $z</em>i$ is the charge of the ions.

49. Activity and Activity Coefficient

• Activity: Effective concentration of a species in solution.

• Activity Coefficient: A factor used to account for deviations from ideal behavior in concentrated solutions.

50. Redox Reactions

• Reactions that involve the transfer of electrons between chemical species, involving oxidation (loss of electrons) and reduction (gain of electrons).

51. Electric Charge, Current, Electrical Potential and Faraday's Constant

• Electric Charge (q): The property of matter that causes it to experience a force when near other electric charges.

• Current (I): The flow of electric charge (measured in Amperes).

• Electrical Potential (E): The potential energy per unit charge (voltage).

• Faraday’s Constant (F): The magnitude of electric charge per mole of electrons (approximately $96485 ext{ C/mol}$).

• Ohm’s Law: $V = IR$, where V is voltage, I is current, and R is resistance.

• Power (P): The rate of doing work (measured in watts), calculated as $P = IV$.

52. Galvanic Cell and Components

• Galvanic Cell: A device that converts chemical energy into electrical energy through spontaneous redox reactions.

• Half-Reaction: The separate oxidation and reduction reactions in a redox process.

• Salt-Bridge: A device used to connect the oxidation and reduction half-cells, allowing ions to flow for charge balance.

• Cathode: The electrode where reduction occurs.

• Anode: The electrode where oxidation occurs.

53. Nernst Equation

• An equation that relates the reduction potential of a half-cell to the standard electrode potential, temperature, and activities of the species: $E = E^ ext{0} - rac{RT}{nF} ext{ln}(Q)$.

54. Definitions Related to Spectroscopy

• Spectroscopy: The study of the interaction between matter and electromagnetic radiation.

• Spectrometry: The measurement of the spectrum of a chemical substance.

• Spectrophotometry: A method of analyzing substances by measuring the intensity of light at specific wavelengths.

55. Wavelength, Frequency, Speed of Light, and Energy of Photon

• Wavelength ($ext{λ}$): The distance between successive peaks of a wave.

• Frequency ($ext{ν}$): The number of cycles of a wave that pass a point in one second.

• Speed of Light ($c$): The speed at which light travels in a vacuum ($c ext{≈ } 3.00 imes 10^8 ext{ m/s}$).

• Energy (photon) ($E$): Calculated using the formula: $E = h<br>u$, where $h$ is Planck's constant ($ext{≈ } 6.626 imes 10^{-34} ext{ J s}$).

56. Beer’s Law

• States that the absorbance of a solution is directly proportional to the concentration of the absorbing species: $A = εcL$, where $A$ is absorbance, $ε$ is the molar absorptivity, $c$ is the concentration, and $L$ is the path length.

57. Absorbance vs Transmittance

• Absorbance ($A$): The logarithmic measure of the amount of light absorbed by the sample: $A = - ext{log}(T)$, where $T$ is transmittance.

• Transmittance ($T$): The ratio of transmitted light to incident light, usually expressed as a percentage.

58. Chromophore, Monochromator, Chemiluminescence, and Cuvet

• Chromophore: A part of a molecule responsible for its color, due to absorption of specific wavelengths.

• Monochromator: An optical device that transmits a selected wavelength or a narrow band of wavelengths of light.

• Chemiluminescence: Emission of light during a chemical reaction.

• Cuvet: A small, usually rectangular vessel used to hold liquid samples for spectroscopic measurements.

59. Absorption of Light by a Molecule

• When a molecule absorbs light, electrons are promoted from a lower energy level to a higher energy level, resulting in an excited state.

60. Total Absorbance of a Mixture

• The total absorbance of a mixture can be calculated as the sum of the absorbances of its components.

61. Isosbestic Point

• A wavelength at which the absorbance of a mixture remains constant despite changes in the concentrations of its components.

62. Scatchard Plot

• A graphical representation used to analyze binding data, providing insights into binding affinities and stoichiometry of interactions.

63. Continuous Variation, Flow Injection Analysis, and Sequential Addition

• Method of Continuous Variation: A technique to determine binding stoichiometries by varying the concentrations of reactants.

• Flow Injection Analysis: An automated analytical technique where a sample is injected into a continuous flow of reagent solution.

• Sequential Addition: A method where reactants are added to a solution one after another to monitor reaction changes.

64. Laminar Flow and Radial Diffusion

• Laminar Flow: A smooth and orderly movement of fluid with minimal mixing between layers.

• Radial Diffusion: The spreading of a substance from an area of high concentration to an area of low concentration in all directions.

65. Sensors Based on Luminescence Quenching

• Analytical devices that utilize the decrease in luminescent signal upon interaction with a quenching agent to determine analyte concentrations.

66. Quantum Yield and Stern-Volmer Equation

• Quantum Yield: The efficiency of photon emission in a luminescence process.

• Stern-Volmer Equation: Relates the luminescence lifetime or intensity to the concentration of a quencher: $rac{I<em>0}{I} = 1 + K</em>q[Q]$, where $I_0$ and $I$ are the intensities without and with quencher, respectively.

67. Atomic Absorption Spectroscopy Experiment

• A technique in which atoms are vaporized in a flame or graphite furnace, and absorbance is measured, allowing for quantitative analysis of elements.

68. Nebulization

• The process of creating a fine mist or aerosol from a liquid, used in atomic absorption and other analytical methods for sample introduction.

69. Aerosol

• A suspension of fine solid particles or liquid droplets in the air or another gas.

70. Advantages of Furnaces over Flames in Atomic Absorption

• Furnaces: Higher temperatures lead to better atomization and increased sensitivity compared to flames, enabling lower detection limits and better precision.

71. Advantages and Disadvantages of Inductively Coupled Plasma (ICP)

• Advantages: High temperature leads to complete atomization; capable of analyzing multiple elements simultaneously with high sensitivity.

• Disadvantages: Requires expensive equipment and is less portable than flame-based techniques.

72. Boltzmann Distribution Equation Application

• Describes the distribution of energy among particles in a system at thermal equilibrium; applies to various phenomena in physical chemistry.

73. Mechanisms that Broaden Lines in Atomic Spectroscopy

• Two primary mechanisms that cause line broadening are Doppler broadening (due to motion of atoms) and pressure broadening (due to collisions between particles).

74. Advantages of Hollow-Cathode Lamps in Atomic Absorption

• Provide narrow spectral lines and high intensity, leading to improved sensitivity and selectivity in atomic absorption measurements.

75. Background Correction in Atomic Absorption

• The process used to account for overlapping signals from sample matrices to enhance the accuracy of the absorbance measurements, often involving the use of a blank or a correction algorithm.

76. Types of Interferences in Atomic Absorption Spectroscopies

• Include spectral interferences, chemical interferences, and physical interferences that can affect the accuracy and precision of measurements.

77. Mass Spectrometry

• An analytical technique that measures the mass-to-charge ratio of ions to identify and quantify compounds in a sample.

78. Components of a Mass Spectrometer

• Source of Ions: Area where ions are generated.

• Mass Separator: Device that separates ions based on their mass-to-charge ratio.

• Detector: Device that registers the separated ions and produces a mass spectrum.

79. Mass Spectrum

• A graphical representation of the mass-to-charge ratios of ionized fragments, used for compound identification.

80. Extraction, Partition Coefficient, and Distribution Coefficient

• Extraction: The process of separating a substance from a mixture by using a solvent.

• Partition Coefficient ($K$): The ratio of concentrations of a compound in two immiscible phases at equilibrium.

• Distribution Coefficient: Similar to partition coefficient but considers total concentrations in both phases.

81. Chromatography

• A technique used to separate components in a mixture based on differences in their distribution between stationary and mobile phases.

• Types of Chromatography: Include gas chromatography (GC), liquid chromatography (LC), and thin-layer chromatography (TLC).

82. Eluent and Eluate

• Eluent: The solvent used to carry the analyte through the stationary phase.

• Eluate: The solution that emerges from the chromatography column after the separation of components.

83. Chromatographic Terms

• Chromatogram: A visual output showing the results of a chromatography experiment.

• Retention Time: The time it takes for a component to traverse the chromatography system.

• Retention Volume: Amount of mobile phase required to elute a component.

• Dead Time: Time taken for an unretained species to elute.

• Adjusted Retention Time: Retention time minus dead time.

• Separation Factor: The ratio of retention times of two components.

• Retention Factor ($R_f$): Ratio of the distance traveled by the analyte to the distance traveled by the solvent front.

84. Plate Height

• A measure of the efficiency of a chromatography column; lower plate heights indicate more efficient separations.

85. Van Deemter Equation

• An equation that relates plate height to flow rate, column properties, and analyte properties, enhancing understanding of chromatographic efficiency.

86. Advantages of Open Tubular Columns

• Provide high efficiency and resolution due to a greater surface area-to-volume ratio and reduced resistance to flow, leading to faster separations.

87. Reversed-phase vs Normal-phase Chromatography

• Reversed-phase Chromatography: Stationary phase is nonpolar, and mobile phase is polar (retains polar compounds well).

• Normal-phase Chromatography: Stationary phase is polar, and mobile phase is nonpolar.

88. Eluent Strength

• Refers to the ability of the eluent to displace solutes from the stationary phase; stronger eluents enhance elution of retained analytes.

89. Gradient Elution vs Isocratic Elution

• Gradient Elution: Composition of the mobile phase changes during the separation process, often leading to improved resolution.

• Isocratic Elution: The mobile phase composition remains constant throughout the separation.

90. Purpose of Hydrophilic Interaction Chromatography (HILIC)

• A specialized form of chromatography that separates polar compounds effectively by utilizing a polar stationary phase and a less polar mobile phase, making it suitable for the analysis of hydrophilic substances.