Analytical Chemistry Chapter 1 PDF

Analytical Chemistry 1 – Nature of Analytical Chemistry Outline of Chapter 1.1 – Definition of Analytical Chemistry 1.2 – Analytical Methods: Classical method vs Instrumental method. 1.3 – Flow of Quantitative Analysis. 1.4 – Methods for Data Analysis. 1.5 – Calculations in Analytical Chemistr...

Analytical Chemistry 1 – Nature of Analytical Chemistry Outline of Chapter 1.1 – Definition of Analytical Chemistry 1.2 – Analytical Methods: Classical method vs Instrumental method. 1.3 – Flow of Quantitative Analysis. 1.4 – Methods for Data Analysis. 1.5 – Calculations in Analytical Chemistry (stoichiometry, concentration, dilution, density and specific gravity and dilution) Further Reading: Analytical Chemistry: An Introduction, 9th Edition (Skoog, Douglas A.; West, Donald; Holler, F. James) 9/15/2024 Prepared By: Analytical Chemistry team 2  1.1. Definition of Analytical Chemistry 1.1 – Definition of Analytical Chemistry Analytical chemistry is a measurement science. It is set of powerful methods that are useful in all fields of science and medicine. It provides quantitative, qualitative and structural information about the analyte. Analytical chemistry is applied throughout industry, medicine and all sciences. Applications - Environment - used to measure pollutants like NOx, SOx and hydrocarbons in atmosphere. Medicine - Quantitative measurement of ionized calcium in blood serum helps diagnose parathyroid diseases in human. Industrial - Analysis of steel during its production allows adjustment of its element concentration such as carbon, nickel and chromium to achieve desired strength and properties Find the definitions of qualitative and quantitative analysis in the reference book 9/15/2024 Prepared By: Analytical Chemistry team 3 1.2 –: Classical method vs Instrumental method. 1.2. Analytical Methods: Classical method vs Instrumental method Analytical Methods Classical Methods Instrumental Methods Classic Methods Inorganic (qualitative) analysis: Systematic scheme to confirm the presence of certain ions or elements by performing a series of reactions that eliminate ranges of possibilities and then confirms suspected ions with a confirming test. Titrimetry (quantitative): Addition of a reactant to a solution being analyzed until some equivalence point is reached. acid – base, redox titrations precipitation titrations complexometric titrations (a colored complex used to determine the end) point Gravimetry (quantitative): Determining the amount of material present by weighing the sample before and/or after some transformation 9/15/2024 Prepared By: Analytical Chemistry team 4  Instrumental Methods 1.2. Analytical Methods: Classical method vs Instrumental method Spectroscopy : Interaction of the atoms or molecules with electromagnetic radiation. Mass Spectrometry : Mass-to-charge ratio of molecules using electric and magnetic fields. 9/15/2024 Prepared By: Analytical Chemistry team 5  1.2. Analytical Methods: Classical method vs Instrumental method Crystallography : A technique that characterizes the chemical structure of materials at the atomic level by analyzing the diffraction patterns of usually x-rays that have been deflected by atoms in the material. 9/15/2024 Prepared By: Analytical Chemistry team 6  1.2. Analytical Methods: Classical method vs Instrumental method Electrochemical Analysis : Interaction of the material with an electric field. Galvanic cell Conductivity meter Thermal Analysis : Calorimetry and thermogravimetric analysis measure the interaction of a material and heat. Thermo-gravimetric Analyzer 9/15/2024 Prepared By: Analytical Chemistry team 7  1.2. Analytical Methods: Classical method vs Instrumental method Separation: Processes are used to decrease the complexity of material mixtures. (Separation of mixture in to its components) Column Chromatography TLC 9/15/2024 Prepared By: Analytical Chemistry team 8  1.2. Analytical Methods: Classical method vs Instrumental method Hybrid Techniques: Combinations of the above techniques produce "hybrid" or "hyphenated" techniques. GC-MS 9/15/2024 Prepared By: Analytical Chemistry team 9  1.2. Analytical Methods: Classical method vs Instrumental method Microscopy :Visualization of single molecules, single cells, biological tissues and nano- micro materials Digital microscope Lab-on-a-chip(LOC): microfluidics or micro total analysis system. The whole device can be visualized under a microscope. Lab on chip 9/15/2024 Prepared By: Analytical Chemistry team 10 1.3 – Flow of Quantitative Analysis. 1.3. Flow of Quantitative Analysis Find the explanation of the diagram in reference book 9/15/2024 Prepared By: Analytical Chemistry team 11 Important terms 1.4. Methods for Data Analysis Stock Solution - Solution with high concentration of the analyte. Standard solution - Solution containing known concentrations of the analyte. Blank solution - Solution containing all the reagents and solvents used in the analysis, but no deliberately added analyte. Analyte & Matrix- An analyte, component, or chemical species is a substance or chemical constituent that is of interest in an analytical procedure, the remainder of the sample is termed as the matrix. 9/15/2024 Prepared By: Analytical Chemistry team 12  1.4. Methods for Data Analysis 1.4 – Methods for Data Analysis Important calibration methods. 1. Calibration curve method 2. Standard addition method 3. Internal standard method 9/15/2024 Prepared By: Analytical Chemistry team 13  1.4. Methods for Data Analysis 1. Calibration curve  The graphic relationship between the reading obtained in analytical process and the quantity of analyte in calibration.  The relationship is often a straight line rather than a curve.  Several standards having different concentrations that is, containing exactly known concentrations of the analyte are measured and the responses are recorded. 9/15/2024 Prepared By: Analytical Chemistry team 14  1. Calibration curve 1.4. Methods for Data Analysis After choosing the best line, the equation of straight line (y=mx+b) will be used to find: x unknown concentration m is the slope b is the intercept on the y-axis. 9/15/2024 Prepared By: Analytical Chemistry team 15  1. Calibration curve 1.4. Methods for Data Analysis Method of least square(how to get best line)  The method of least square is widely The vertical used technique for finding a line (or deviation a curve) through a set of data points that have some scatter and do not lie perfectly on a straight line.  idea of the least square method is to minimize the vertical deviation between the line and the points. 9/15/2024 Prepared By: Analytical Chemistry team 16  1.4. Methods for Data Analysis 2. Method of Standard Addition Known quantities of standard are added to the unknown. Both the standard and the unknown are containing the analyte (standard containing known analyte concentration, Unknown containing unknown analyte conc.) From the increase in signal, we deduce how much analyte was in the unknown. Appropriate(useful) when the sample composition is unknown or complex and affects the analytical signal. Matrix and Matrix effect. (advantage). Time consuming.(disadvantage). 9/15/2024 Prepared By: Analytical Chemistry team 17 Q1) Students performed an experiment in which each flask contained 25.00 mL of serum varying addition of 2.64 M Na standard and a total volume of 50mL. Find the concentration of Na in the serum. Flask Volume of standard (ml) Signal 1 0 3.13 2 1.00 5.40 3 2.00 7.89 4 3.00 10.30 5 4.00 12.48 9/15/2024 Prepared By: Analytical Chemistry team 18 Q1) Students performed an experiment in which each flask contained 25.00 mL of serum varying addi on of 2.64 M Na standard and a total volume of 50mL. Find the concentra on of Na in the serum. Flask Volume of standard Signal 1 0 3.13 2 1.00 5.40 3 2.00 7.89 4 3.00 10.30 5 4.00 12.48 A1: Flask Volume of standard Concentra on of standard Signal 1 0 0.0000 3.13 2 1.00 0.0528 5.40 3 2.00 0.1056 7.89 4 3.00 0.1584 10.30 5 4.00 0.2112 12.48  1.4. Methods for Data Analysis 3. Method of Internal Standard known amount of a standard (containing a substance, different from analyte but with similar properties), is added to the unknown (note that the analyte is present in the unknown only). Signal from analyte is compared with signal from the internal standard to find out how much analyte is present in the unknown. useful when the quantity of sample analyzed or the instrument response varies slightly from run to run for reasons that are difficult to control. Internal standards are also desirable (useful) when sample loss can occur during sample preparation steps prior to analysis. 9/15/2024 Prepared By: Analytical Chemistry team 19  3. Method of Internal Standard 1.4. Methods for Data Analysis The concentration of the analyte is found using the following equation: oThe [X] and [S] are the concentrations of analyte and standard after they have been mixed together. oThe response factor equation [F] is predicated to give a linear response to both the analyte and the standard. 9/15/2024 Prepared By: Analytical Chemistry team 20 Q2) In a Chromatography analysis a solution was prepared with 0.0837M octane and 0.0666M nonane. Each one produces a peak area of Ao = 423 and An = 347. 10mL of 0.146 M nonane was added to 10mL of unknown sample and the sample diluted to 25mL. The peak areas obtained were Ao= 553 and An= 582. Find the concentration of octane in the unknown? 9/15/2024 Prepared By: Analytical Chemistry team 21  1.5. Calculations in Analytical Chemistry (stoichiometry, concentration, dilution, density and specific gravity of solutions) 1.5. Calculations in Analytical Chemistry Prefix Symbol Factor Prefix Symbol Factor yotta Y 1024 deci d 10¯1 zetta Z 1021 centi c 10¯2 exa E 1018 milli m 10¯3 peta P 1015 micro µ 10¯6 tera T 1012 nano n 10¯9 giga G 109 pico p 10¯12 mega M 106 femto f 10¯15 kilo k 103 atto a 10¯18 hecto h 102 zepto z 10¯21 deca da 101 yocto y 10¯24 9/15/2024 Prepared By: Analytical Chemistry team 22 STOICHIOMETRY The calculation of quantities of substances involved in a chemical reaction 9/15/2024 Prepared By: Analytical Chemistry team 23 Converting grams to grams We cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) To make the jumps between steps Molar mass of x Molar mass of y grams (x)  moles (x)  moles (y)  grams (y) Mole ratio from balanced equation 9/15/2024 Prepared By: Analytical Chemistry team 24 EXAMPLE 𝟐𝟓. 𝟎 𝒈 𝑵𝒂𝟐 𝑺𝑶𝟒 → ? 𝒈 𝑵𝒂 𝟐𝟓. 𝟎 𝒈 𝑵𝒂𝟐 𝑺𝑶𝟒 → 𝒎𝒐𝒍𝒆 𝑵𝒂𝟐 𝑺𝑶𝟒 → 𝒎𝒐𝒍𝒆 𝑵𝒂 → 𝒈 𝑵𝒂 Molar mass of Mole Ratio Molar mass of Na+ Na2SO4 𝟏 𝒎𝒐𝒍𝒆 𝑵𝒂𝟐 𝑺𝑶𝟒 𝟐 𝒎𝒐𝒍𝒆 𝑵𝒂 𝟐𝟐. 𝟗𝟗 𝒈 𝑵𝒂 𝟐𝟓. 𝟎 𝒈 𝑵𝒂𝟐 𝑺𝑶𝟒 𝒙 𝒙 𝒙 𝟏𝟒𝟐. 𝟎 𝒈 𝑵𝒂𝟐 𝑺𝑶𝟒 𝟏 𝒎𝒐𝒍𝒆 𝑵𝒂𝟐 𝑺𝑶𝟒 𝟏 𝒎𝒐𝒍𝒆 𝑵𝒂 = 𝟖. 𝟏𝟎 𝒈 𝑵𝒂 9/15/2024 Prepared By: Analytical Chemistry team 25  Calculating the Amount of a Substance in Moles or millimoles EXAMPLE 9/15/2024 Prepared By: Analytical Chemistry team 26 Practice Questions: Q3) How many grams of Na+ (22.99 g/mol) in 50g of NaCl (58.44 g/mol)? Q4) How many grams of Na+ (22.99 g/mol) in 2.92g of Na3PO4 (163.94 g/mol)? Q5) How many grams of K+ (39.10 g/mol) in 34.1 mmol of K2HPO4? Q6) How many mg of C (12.01 g/mol) in 0.33g CaC2O4 (128.097 g/mol)? 9/15/2024 Prepared By: Analytical Chemistry team 27  Concentration Scales Molarity is a temperature-dependent scale because volume (and density) change with temperature. Moles of solute Molarity (M) = Liter of solution Molality is a temperature-independent scale because the mass of a kilogram does not vary with temperature. Moles of solute Molality (m) = kg solvent 9/15/2024 Prepared By: Analytical Chemistry team 28  Concentration Scales Percent Concentration 𝒘𝒆𝒊𝒈𝒉𝒕 𝒔𝒐𝒍𝒖𝒕𝒆 𝒘𝒆𝒊𝒈𝒉𝒕 𝒑𝒆𝒓𝒄𝒆𝒏𝒕 𝒘/𝒘 = × 𝟏𝟎𝟎% 𝒘𝒆𝒊𝒈𝒉𝒕 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 e.g. : nitric acid is sold as a 70 % solution, which means that the reagent contains 70 g of HNO3 per 100 g of solution 𝒗𝒐𝒍𝒖𝒎𝒆 𝒔𝒐𝒍𝒖𝒕𝒆 𝒗𝒐𝒍𝒖𝒎𝒆 𝒑𝒆𝒓𝒄𝒆𝒏𝒕 𝒗/𝒗 = × 𝟏𝟎𝟎% 𝒗𝒐𝒍𝒖𝒎𝒆 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 e.g. : a 5% aqueous methanol solution is a solution prepared by diluting 5.0 mL of pure methanol with enough water to give 100 mL of solution 𝒘𝒆𝒊𝒈𝒉𝒕 𝒔𝒐𝒍𝒖𝒕𝒆 𝒘𝒆𝒊𝒈𝒉𝒕/𝒗𝒐𝒍𝒖𝒎𝒆 𝒑𝒆𝒓𝒄𝒆𝒏𝒕 𝒘/𝒗 = × 𝟏𝟎𝟎% 𝒗𝒐𝒍𝒖𝒎𝒆 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 e.g. :5% aqueous silver nitrate refers to a solution prepared by dissolving 5 g of silver nitrate in enough water to give 100 mL of solution. 9/15/2024 Prepared By: Analytical Chemistry team 29  Concentration Scales Weight / weight (w/w) basis  mass solute ( g )  2 % (w/w) =  10  percent  mass sample ( g )   mass solute ( g )  3 ppt (w/w) =  mass sample ( g ) 10  ppt = parts per thousand    mass solute ( g )  6 ppm (w/w) =  10  ppm = parts per million  mass sample ( g )   mass solute ( g )  9 ppb (w/w) =  10  ppb = parts per billion  mass sample ( g )   mass solute ( g )  12 ppt (w/w) =  10  ppt = parts per trillion  mass sample ( g )  This scale is useful for solids or solutions. 9/15/2024 Prepared By: Analytical Chemistry team 30  Concentration Scales Weight / volume (w/v) basis  mass solute ( g )  2 % (w/v) =  10  percent  vol. sample (mL)   mass solute ( g )  3  ppt = parts per thousand ppt (w/v) =  10  vol. sample ( mL )   mass solute ( g )  6  ppm = parts per million ppm (w/v) =  10  vol. sample ( mL )   mass solute ( g )  9  ppb = parts per billion ppb (w/v) =  10  vol. sample (mL)   mass solute ( g )  12  ppt = parts per trillion ppt (w/v) =  10  vol. sample (mL)  9/15/2024 Prepared By: Analytical Chemistry team 31  Concentration Scales Volume / volume (v/v) basis  vol. solute (mL)  2 % (v/v) =  10  percent  vol. sample ( mL )   vol. solute (mL)  3 ppt (v/v) =  10  ppt = parts per thousand  vol. sample ( mL )   vol. solute (mL)  6 ppm (v/v) =  10  ppm = parts per million  vol. sample ( mL )   vol. solute (mL)  9 ppb (v/v) =  10  ppb = parts per billion  vol. sample (mL)   vol. solute (mL)  12  ppt = parts per trillion ppt (v/v) =  10  vol. sample ( mL )  9/15/2024 Prepared By: Analytical Chemistry team 32  Concentration Examples  37.0 g HCl  2  10 = 𝟑𝟕. 𝟎%(𝒘/𝒘)  100.0 g solution   Alcoholic beverage  4.00 mL CH 3CH 2OH  2 = 𝟏𝟎. 𝟒% (𝒗/𝒗)  10  38. 5 mL beverage   Color indicator for titrations  0.050 g phenolphthalein  2  10 = 𝟎. 𝟏𝟎% (𝒘/𝒗)  50.0 mL solution  9/15/2024 Prepared By: Analytical Chemistry team 33  Concentration Scales Parts per million, billion, trillion are very often used to denote concentrations of aqueous solutions:  1 g solute  103 mg  1 g solution  1000 mL solution  mg 1 ppm   6      1  10 g solution  1 g  1mL solution  1 L solution  L    It will be very useful to memorize: 1 part per million (ppm) = 1 mg / L 1 part per billion (ppb) = 1 μg / L 1 part per trillion (ppt) = 1 ng / L 9/15/2024 Prepared By: Analytical Chemistry team 34  Concentration Scale (ppm) is the number of parts of Parts per million, solute in one million parts or ppm of solution. Concentration in ppm is calculated using the following formulae: 1 part per million (ppm) = 1 mg / L 9/15/2024 Prepared By: Analytical Chemistry team 35  Concentration Examples : Molarity EXAMPLE Molar concentration (M) = mol /L 𝟏 𝒎𝒐𝒍𝒆 𝑪𝟐 𝑯𝟓 𝑶𝑯 𝟏 𝟐. 𝟑𝟎 𝒈 𝑪𝟐 𝑯𝟓 𝑶𝑯 𝒙 𝒙 𝟒𝟔. 𝟎𝟕 𝒈 𝑪𝟐 𝑯𝟓 𝑶𝑯 𝟑. 𝟓𝟎 𝑳 𝒎𝒐𝒍 = 𝟎. 𝟎𝟏𝟒𝟑 𝑪𝟐 𝑯𝟓 𝑶𝑯 𝑳 = 𝟎. 𝟎𝟏𝟒𝟑 𝑴 9/15/2024 Prepared By: Analytical Chemistry team 36  Concentration Examples : Molarity EXAMPLE Describe the preparation of 2.00 L of 0.108 M BaCl2.2H2O from BaCl2.2H2O (244.3 g / mol).  0.108 BaCl2.2H2O mol  244.3 g BaCl2.2H2O  2.00 Lx     L  mol   52.8 gBaCl2.2H2O Note: the students need to explain the preparation procedure 9/15/2024 Prepared By: Analytical Chemistry team 37  Dilution A volume of the concentrated solution is transferred to a fresh container and diluted to the desired final volume The total number of moles of solutes in the solution remains the same after dilution, but the volume of the solution becomes greater. Calculating Dilution M 1 V 1 = M2 V 2 9/15/2024 Prepared By: Analytical Chemistry team 38  Dilution EXAMPLE You have available 12.0 M HCl and wish to prepare 0.500 L of 0.750 M HCl to use it in an experiment. How can you prepare such a solution? C1 V1 = C2 V2 C1 = 12.0 mol L-1 C2 = 0.750 mol L-1 V1 = ? V2 = 0.500 L V1 = (C2)(V2) / C1 V1 = (0.750 mol L-1) (0.500 L) / 12.0 mol L-1 V1 = 3.12 x 10-2 L = 31.2 mL 9/15/2024 Prepared By: Analytical Chemistry team 39  Concentration Examples : Molarity EXAMPLE Describe how would you prepare 200 mL of 1.0 mol/L HCl solution from a 50.0 mol/L HCl stock solution. C1 V1 = C2 V2 C1 = 50.0 mol L-1 C2 = 1 mol L-1 V1 = ? V2 = 0.200 L V1 = (C2)(V2) / C1 V1 = (1 mol L-1) (0.200 L) / 50.0 mol L-1 V1 = 4 x 10-3 L = 4 mL 9/15/2024 Prepared By: Analytical Chemistry team 40  Concentration Examples : %(w/v) EXAMPLE What is the concentration, on a %(w/v) basis, of V in a solution that contains 281.5 mg/L of V?  mass solute ( g )  2 % ( w / v)   10  vol. sample (mL)   281.5 mg W  1 g V  1L  2 % ( w / v)      10  L  1000 mg V   1000 mL   0.02815 % ( w / v) or 2.815 x 10  2 % ( w / v) 9/15/2024 Prepared By: Analytical Chemistry team 41  Concentration Examples : %(w/v) EXAMPLE Describe the preparation of 500 mL of 4.75 % (w/v) aqueous ethanol (C2H5OH, 46.1 g/mol).  mass solute ( g )  2 % ( w / v)   10  vol. sample (mL)   4.75 g  500 mL        100 mL    4.75 g  500        100    23.75 g  23.8 g 9/15/2024 Prepared By: Analytical Chemistry team 42  Concentration Examples : (ppm) EXAMPLE A student add 11 mg of sulfuric acid to 2,000 grams of water. What is the resulting concentration of sulfuric acid, in ppm? convert from milligrams to grams: Then you simply plug the numbers into the formula: 9/15/2024 Prepared By: Analytical Chemistry team 43  Concentration Examples : (ppm) EXAMPLE What is the molarity of K+ in a solution that contains 63.3 ppm of K3Fe(CN)6 (329.3 g/ mol)? A concentrated butanol (74.12 g/mol) solution has a concentration of 809.757x109 ppt (trillion) calculate the molar concentration of the solution. 9/15/2024 Prepared By: Analytical Chemistry team 44  Concentration Examples : (ppm) EXAMPLE Find the mass required to prepare a solution of 50 ppm N in 1 L volumetric flask by using KNO3. Answer: 1 part per million (ppm) = 1 mg / L 50 ppm N = 50 mg/ L N grams (N)  moles (N)  moles (KNO3)  grams (KNO3) 9/15/2024 Prepared By: Analytical Chemistry team 45  Conversion of Molarity to ppm EXAMPLE A solution of 0.02500 M K2SO4.What is concentration of K+ (in ppm) in this solution?  0.02500 mol K 2 SO4  2 mol K  39.10 g  1000 mg           L  1 mol K 2 SO4  mol K  g  mg K   1955 L  1955 ppmK  9/15/2024 Prepared By: Analytical Chemistry team 46  Conversion of Molarity to ppm EXAMPLE Convert the concentration of a solution of 0.02500 M K2SO4 into ppm K2SO4.  0.02500 mol K 2 SO4  174.26 g K 2 SO4  1000 mg       L  mol K 2 SO4  g  mg K 2 SO4  4356 L  4356 ppm 9/15/2024 Prepared By: Analytical Chemistry team 47  Density and Specific Gravity of Solutions Density Specific Gravity the ratio of its density its mass per m to the density of an unit volume v equal volume of water at 4°C Kg/L or g/mL unit less Since the density of water is approximately 1.00 g/mL and, density and specific gravity are used interchangeably. 9/15/2024 Prepared By: Analytical Chemistry team 48  Density and Specific Gravity of Solutions EXAMPLE Calculate the molar concentration of HNO3 (63.0 g/mol) in a solution that has a specific gravity of 1.42 and is 70.5% HNO3 (w/w). 9/15/2024 Prepared By: Analytical Chemistry team 49 Practice 1) In an original propanol bottle, the concentration and density of propanol is 99.7% (v/v) and 0.785 g/mL. a) Calculate the molar concentration of propanol (60.09 g/mol). b) Calculate the concentration of propanol in ppm. c) Describe the preparation of 3000ppm propanol solution in 25mL volumetric flask. 9/15/2024 Prepared By: Analytical Chemistry team 50 Practice 2) A 6.42% (w/w) Fe(NO3)3 (241.86 g/mol) solution has a density of 1.059 g/mL. Calculate the following. a) The molar concentration of Fe(NO3)3 in this solution. b) The NO3- molar concentration in the solution. c) The mass in grams of Fe(NO3)3 contained in each liter of this solution. 9/15/2024 Prepared By: Analytical Chemistry team 51