chem

• Elements are organized in the periodic table according to their atomic number, electron configurations and chemical properties.
• Analytical Chemistry is a measurement science that deals with the identification, separation, and determination of relative amounts of components present in a sample
• Nature and Scope of Analytical Chemistry includes identifying, classifying, isolating, measuring/quantifying an analyte, gathering data, and data analysis/interpretation
• Analytical Chemistry serves as an important tool in various fields and applications such as quality control, manufacturing industries, clinical diagnoses, environmental monitoring, geological assays, agriculture, and forensic science
• Divisions of Analytical Chemistry: Qualitative, Quantitative, and Structural Analysis
• Qualitative Analysis establishes the chemical identity of species in a sample, while Quantitative Analysis determines the relative amounts of species in a sample
• Structural Analysis involves determining the spatial arrangement of atoms in an element/molecule or identifying characteristic groups of atoms (functional groups)
• Analyte refers to the components of a sample to be determined, such as sugar content in blood, WBC, RBC, pH, etc.
• Matrix is the remainder of the material or sample in which the analyte forms a part, containing all the components that include the analyte
• Friedrich Wilhelm Ostwald, a pioneer in analytical chemistry, recognized the importance of thermodynamics and catalysis
• Analytical Data is required in various disciplines and situations, not just in chemistry but also in science, art, space science, clinical diagnoses, etc.
• Classification of Quantitative Analysis methods: Gravimetric, Volumetric, and Instrumental methods (Electroanalytical and Spectroscopic methods)
• Gravimetric Methods determine the mass of an analyte, while Volumetric Methods measure the volume of a solution containing sufficient reagent to react completely with the analyte
• Electroanalytical Methods involve measuring electrical properties like voltage, current, resistance, and quantity of electrical charge
• Spectroscopic Methods measure the interaction between electromagnetic radiation and analyte atoms or molecules, such as ICP, AAS, UV-VIS spectrophotometer
• Different Types of Spectroscopies include Atomic Spectroscopy, Ultraviolet and Visible Spectroscopy, Infrared Spectroscopy, Raman Spectroscopy, and Nuclear Magnetic Resonance
• Classification of Quantitative Analysis: Ultimate Analysis, Proximate/Selective Analysis, and Single-component Analysis
• Types of Measurement include weight or volume of analyte (Macro, Semi-micro, Micro, Ultra-micro) and amount of analyte (Major, Minor, Trace, Ultra-trace Constituents)
• Steps in Quantitative Analysis involve selecting a method, acquiring a sample, processing the sample, eliminating interferences, calibration and measurement, calculating results, and evaluating results
• Sampling step in analytical chemistry:

  • Heterogeneous Material: constituent parts can be distinguished visually or with the aid of a microscope
  • Assay: process of determining the amount of a given sample material indicated by its name
  • Sampling: obtaining a small mass of a material that accurately represents the bulk of the material being sampled
• Processing a sample in analytical chemistry:

  • Preparing a laboratory sample:
  • Solid laboratory sample: ground to decrease particle size, mixed for homogeneity, stored before analysis (absorption or desorption of water may occur, best to dry samples beforehand), determination of moisture content, prevent contamination
  • Liquid laboratory sample: keep inside a clean, sealed container to avoid evaporation or loss of solvent, prevent contamination of atmospheric gases (always preserve the integrity of the sample)
  • Defining Replicate Samples: portions of a material of approximately the same size carried through an analytical procedure in the same way at the same time, quantitative measurement on replicates is usually averaged, various statistical tests are performed on the results to establish reliability
• Preparing Solutions in analytical chemistry:

  • Most analyses are performed in solutions
  • A proper solvent should dissolve the entire sample, including the analyte, rapidly and completely
  • If analytes are insoluble, convert analyte into a form that is soluble, but the amount of analyte can still be measured (e.g., heating with aqueous solutions with strong acids, strong bases, oxidizing/reducing agents, or combination)
• Eliminating Interferences in analytical chemistry:

  • Eliminate substances from the sample that may interfere with the measurement step
  • Interferences / Interferents: species other than the analytes that cause errors by enhancing or attenuating the quantity being measured
• Calibration and Measurement in analytical chemistry:

  • Analytical results depend on a final measurement X of a physical or chemical property of the analyte
  • Property may vary in a known and reproducible way with the concentration of the analyte (CA)
  • Calibration determines the proportionality between CA and a measured quantity, a process of determining a proportionality constant k
• Calculating Results in analytical chemistry:

  • Calculated using raw experimental data obtained in the measurement step, characteristics of the measurement instruments, and stoichiometry of the analytical reaction
• Evaluating Results by Estimation of Reliability in analytical chemistry:

  • Analytical results are incomplete without an estimate of their reliability
  • The experimenter must provide some measure of the uncertainties associated with computed results for the data to have any value
  • Involves the use of statistical tools to determine if data obtained is reliable and if the analysis is to be accepted, discarded, or repeated
• Significant Figures in Numerical Computations:

  • All the certain digits plus the first uncertain digit
  • Rules for addition/subtraction and multiplication/division with significant figures
  • Scientific notation, rounding off data, and rules for rounding off numbers
• Systeme International d’Unites (SI Unit):

  • International System of Units based on the seven fundamental base units
  • Numerous other useful units derived from these base units
  • Angstrom Unit (Å) is a non-SI unit of length widely used to express the wavelength of very short radiation such as X-rays
• Mole (mol):

  • SI unit for the amount of a chemical species that contains exactly the Avogadro number (6.022 × 10^23) particles
• Atomic Mass Unit (amu) and Molar Mass:

  • Atomic mass unit (amu) is based on a relative scale with the reference being the 12C carbon isotope assigned a mass of exactly 12 amu
  • Molar mass of any element is the mass in grams of 6.022 × 10^23 atoms of that element
• Molar mass of an element is the mass in grams of 6.022 × 10^23 atoms of that element, numerically equal to the atomic mass of the element in amu units

  
• Relationships Between Units:

  • 1 Mole ≈ 1000 mmols
  • 1g ≈ 1000 mg
  • 1L ≈ 1000mL
  • Gram/mole is numerically the same as mg/mmol
  • Mole/L is numerically the same as mmol/ml
• Molar mass or molecular weight is the sum of the total mass in grams of the atoms present to make up a molecule per mole, expressed in grams/mole
• Expressing Solution Concentrations:

  • Molar concentration (cx) is the number of moles of the solute species in one liter of the solution
  • Analytical molarity gives the total number of moles of a solute in 1L of the solution
  • Equilibrium molarity expresses the molar concentration of a particular species in a solution at equilibrium
• Percent is parts per hundred of a sample, while percent concentration expresses concentrations in terms of percent (parts per hundred)
• Density is the mass of a substance per unit volume, expressed in units of kg/L or g/L, calculated as mass/volume
• Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water, having no units
• Heat and temperature are not the same; temperature is a measure of the intensity of heat in a body
• Redox reactions are vital to basic life functions like photosynthesis, respiration, combustion, and corrosion, involving oxidation and reduction reactions occurring simultaneously
• Rules for Assigning Oxidation Numbers:

  • The oxidation number of a free element is always 0
  • The oxidation number of a monatomic ion equals the charge of the ion
  • The usual oxidation number of hydrogen is +1, but -1 in compounds with less electronegative elements
  • The oxidation number of oxygen in compounds is usually -2, except in specific cases