ANALYTICAL CHEMISTRY INTRODUCTION AND REVIEW

What is analytical chemistry? The science of inventing and applying the concepts, principles and strategies for measuring the characteristics of chemical systems and species The science of inventing and applying the concepts, principles and strategies for measuring the characteristics of chemical systems and species often described as the area of chemistry responsible for characterizing the composition of matter often described as the area of chemistry responsible for characterizing the composition of matter Qualitative analysis An analysis in which we determine the identity of the constituent species in a sample An analysis in which we determine the identity of the constituent species in a sample Quantitative analysis An analysis in which we determine how much of a constituent species is present in a sample. An analysis in which we determine how much of a constituent species is present in a sample.

The analytical problems characterization analysis An analysis in which we evaluate a sample’s chemical or physical properties An analysis in which we evaluate a sample’s chemical or physical properties fundamental analysis An analysis whose purpose is to improve an analytical method’s capabilities An analysis whose purpose is to improve an analytical method’s capabilities Example, d eterminations of -chemical structure, -equilibrium constants, -particle size, -and surface structure Example: -Extending and improving the theory -studying a method’s limitations, -designing new and modifying old methods

The analytical process

Gravimetric method Classification of quantitative method of analysis Volumetric method ThemeGallery is a Design Digital Content & Contents mall developed by Guild Design Inc. Volume is measured or used to determine amount of sample via concentration Mass is measured Instrumental method Use an instrumental technique to assay the amount of sample

Fundamental SI Units MeasurementUnitSymbol masskilogramkg volumeliterL distancemeterm temperaturekelvinK timeseconds currentampereA amount of substancemolemol

SI Units and non SI Unit

Fundamental SI Units ExponentialPrefixSymbol tera-T 10 9 giga-G 10 6 mega-M 10 3 kilo-k deci-d centi-c milli-m micro- μ nano-n pico-p femto-f atto-a 1 mL = 1x10 -3 L 1 L = 1x10 3 mL 1  L = 1x10 -6 L 1 L = 1x10 6  L 1 attoliter = 1x L 1 L = 1x10 18 attoliter

Review of stoichiometry A. Empirical vs molecular or structural formulas: 1. Empirical formulas  give information only about the simplest ratio between the different elements composing the molecule. Example: HO, H 2 CO 2. Molecular formulas  give information about the numbers of atoms of each element found in the molecule. Example: H 2 O 2, H 4 C 2 O 2, C 2 H 5 OH, C 2 H 4 O 2, C 3 H 6 O 3, C 6 H 12 O 6 3. Structural formulas  give information about the structure of the molecule as well as the numbers of atoms of each element Example: HOOH, (CH 3 ) 3 COH, CH 3 CH 2 OCH 2 CH 3 A. Empirical vs molecular or structural formulas: 1. Empirical formulas  give information only about the simplest ratio between the different elements composing the molecule. Example: HO, H 2 CO 2. Molecular formulas  give information about the numbers of atoms of each element found in the molecule. Example: H 2 O 2, H 4 C 2 O 2, C 2 H 5 OH, C 2 H 4 O 2, C 3 H 6 O 3, C 6 H 12 O 6 3. Structural formulas  give information about the structure of the molecule as well as the numbers of atoms of each element Example: HOOH, (CH 3 ) 3 COH, CH 3 CH 2 OCH 2 CH 3

Solution Total solution Solvent Solute Preparation of solution Solute: a minor species in a solution Solvent: a major species in a solution Example: glucose solution Glucose is a solute Water is a solvent

Molar Concentration Molarity:  The number of moles of solute per 1 liter of solution (M) Concentration  Concentration  a general measurement unit stating the amount of solute present in a known amount of solution

Molality and density Molality Weight = Volume x density Molality: Molality: expresses the mol of substance/solute per unit mass of solvent

Percent Concentration

Part per hundred (pph), thousand (ppt), million (ppm) and billion (ppb)

Units for Reporting Concentration NameUnitsSymbol molarityM normalityN molalitym weight % w/w volume % v/v weight-to-volume % w/v parts per millionppm parts per billionppb EW=equilibrium weight

Example g of NaCl in 1.00 L of water has concentration of _____ mol/L MW of NaCl = 58.5 g/mol

Example g of H 2 SO 4 in 1.00 L of water has concentration of _____ mol/L MW of H 2 SO 4 = 98.0 g/mol

Example 3 What is the w/w % of aqueous ammonia (NH 3 ) solution at 14.3 M with density = 0.9 g/mL (900 g/L)? Solute: NH 3 1)MW of NH 3 = 17.0 g/mol 2)Mole of NH 3 at 14.3 M in 1.00 L = 14.3 mol/L x 1.00 L = 14.3 mol 3)Weight of NH 3 at 14.3 M in 1.00 L = mole of NH 3 x MW of NH 3 = 14.3 mol x 17.0 g/mol = 243 g 4)Weight of 1.00 L solution = volume x density = 1.00 L x 900 g/L = 900 g =27.0%

Example 4 What is the molar concentration of aqueous ammonia (NH 3 ) solution with density = 0.9 g/mL (900 g/L) and 27.0% (w/w)? Solute: NH 3 MW of NH 3 = 17.0 g/mol Weight of NH 3 =mole of NH 3 x MW of NH 3 = C NH 3 x V NH 3 x MW of NH 3 Weight of 1.00 L solution = volume x density = 1.00 L x 900 g/L = 900 g W NH 3 = C NH 3 x V NH 3 x MW of NH 3 = 243 g C NH 3 = 14.3 mol/L = 14.3 M

Example 5 What is the v/v % of ethanol in a solution prepared by mixing 5.00 mL of ethanol with enough water to give 1.00 L of solution? Solute: ethanol 1)Volume of solute (ethanol) = 5.00 mL = 5.00 x L 2)Volume of solution = 1.00 L 3)Volume percent (v/v) =

Stoichiometric Calculation Stoichiometric calculation are based on the combining ratios of reactants which result in specific products. 1. They are expressed in terms of moles 2. When you are given the mass of reactant or product, you should first convert the mass to moles to determine the amount of reactant that will be consumed or product that will be produced for a given reaction 3. If the final answer is to be given in a mass unit, then the moles must be converted to grams 4.

Volumetric Calculations Dilution: the number of moles are the same in dilute and concentrated solution Dilution: the number of moles are the same in dilute and concentrated solution moles = C concentrated V concentrated = C dilute V dilute Units: V=either in L and mL C=M(mol/L) or mM (mmol/L) Be sure to match units for both dilute and concentrated solutions

Stoichiometric Calculation (1) What mass of AgNO 3 (MW = g/mol) is needed to convert 2.33 g of Na 2 CO 3 (MW = g/mol) to Ag 2 CO 3 ? 1 mol2 mol

Stoichiometric Calculation (2) What mass of Ag 2 CO 3 (MW = g/mol) will be formed ? 1 mol

Stoichiometric Calculation (3) To prepare a solution with M of Cl - from BaCl 2.2H 2 O. How much of BaCl 2.2H 2 O must be used to prepare 1.00 liter of solution? Assume BaCl 2 completely dissociates: 1 mol x mol 2 mol 0.5 mol/L x 1.00 L x mol = mole of BaCl 2 (mol) = 0.5/2 = 0.25 mol MW of BaCl 2.2H 2 O = g/mol W of BaCl 2.2H 2 O = mole of BaCl 2 (mol) x MW of BaCl 2.2H 2 O = 0.25 mol x g/mol=61.1 g

Stoichiometric Calculation (4) How many L of a 50 mol/L solution are required to make 200 mL of a 1 mol L -1 solution? moles = C concentrated V concentrated = C dilute V dilute