Analytical Chemistry Basics

Analytical Chemistry

Qualitative and Quantitative Analysis

• Qualitative analysis: Identify unknown elements, ions, or compounds
• Quantitative analysis: Determine the quantity or concentration of elements, ions, or compounds

Quantities and Concentrations

Quantities

• Types of quantities:
  • Weight of substance (mg, g, kg)
  • Number of atoms, ions, or molecules
  • Number of moles (mol)
  • Number of equivalents (equ)
• Moles (mol) = weight of substance (g) / molecular weight (g/mol)
• Avogadro's number: 6.023 x 10^23 molecules/mol

Conversion Factor

• Example: Calculate the amount of silver in 4.14 g of silver carbonate

Problems

• How many grams of sodium carbonate react with 4.0 g of calcium chloride?
• Calculate the weight of the precipitated calcium carbonate
• How many grams of nitrogen are present in 100 kg of ammonium nitrate fertilizer?

Quantities in Equivalents

• Equivalent (equ) = moles x oxidation number (O.N.)
• Equivalent weight (equ wt) = molecular weight (g/mol) / O.N.
• Example: Calculate the equivalent weight of HCl, H2SO4, and H3PO4

Oxidation Number (O.N.)

• Definition: Oxidation state of an atom or ion in a chemical compound
• Rules:
  • Free element (Fe, S, H, Cl): O.N. = 0
  • Ion: O.N. = charge
  • Hydrogen in most compounds: O.N. = +1
  • Oxygen in most compounds: O.N. = -2

Solutions

• Types of solutions:
  • Solid in solid: alloys (e.g., brass: 20% zinc, 80% copper)
  • Solid in liquid: salt solution in water
  • Solid in gas: smoke (carbon in air)
  • Liquid in solid: jelly
  • Liquid in liquid: alcohol (ethyl alcohol in water)
  • Liquid in gas: water vapor in air
  • Gas in solid: homogeneous mixture of hydrogen gas and palladium metal
  • Gas in liquid: soda water
  • Gas in gas: air

Concentrations

• Types of concentrations:
  • Percentage concentrations (%w/w, %w/v, %v/v, %v/w)
  • Part per million (ppm, mg/Kg, mg/L)
  • Molar concentration (M, molarity)
  • Molal concentration
  • Normal concentration (N, normality)
  • Mole fraction (Xi)

Percentage Concentrations

• Calculations:
  • w/w: weight of solute / weight of solution x 100
  • w/v: weight of solute / volume of solution x 100
  • v/w: volume of solute / weight of solution x 100
  • v/v: volume of solute / volume of solution x 100

Molar and Normal Concentrations

• Molarity (M): moles of solute / liters of solution
• Normality (N): moles of solute / liters of solution x O.N.
• Interchangeable: N = M x O.N.

Concentration Problems

• Examples:
  • Prepare a 200 mL 5% NaCl solution
  • Prepare a 500 mL 0.2M Na2CO3 solution
  • Prepare a 0.5L 15% EtOH solution

Dilution Calculations

• Types of dilution:
  • Dilution with water addition
  • Dilution with more diluted solution

Examples

• Prepare 2.0 L diluted sulfuric acid (5% w/v) from concentrated acid (98% w/v)
• A concentrated glucose solution (2 M, 5 mL) was added to 25 mL diluted solution (0.2 M); find the molarity of the final solution