SI Units and Concentration Calculations

SI Units and Prefixes

• Time - 1 minute = 60 seconds
• Liter - 1 liter = 1 cubic decimeter (dm³) = 10⁻³ cubic meters (m³)
• Angstrom - 1 Angstrom = 0.1 nanometer (nm) = 10⁻¹⁰ meters (m)
• Prefixes - A system for denoting multiples and submultiples of SI units using specific symbols:
  • atto (a) - 10⁻¹⁸
  • femto (f) - 10⁻¹⁵
  • pico (p) - 10⁻¹²
  • nano (n) - 10⁻⁹
  • micro (µ) - 10⁻⁶
  • milli (m) - 10⁻³
  • centi (c) - 10⁻²
  • deci (d) - 10⁻¹
  • deka (da) - 10¹
  • hecto (h) - 10²
  • kilo (k) - 10³
  • mega (M) - 10⁶
  • giga (G) - 10⁹
  • tera (T) - 10¹²
  • peta (P) - 10¹⁵
  • exa (E) - 10¹⁸

Concentration Calculations

• Molarity - moles of solute per liter of solution
• Normality - grams of solute per gram molecular weight × liter of solution
• Example 1: A 1-liter solution containing 10g of sodium hydroxide (NaOH)
  • Molar mass of NaOH = 40 g/mol
  • Molarity = 10 g / (40 g/mol × 1 L) = 0.25 M
• Example 2: A 1-liter solution containing 24.5 g of sulfuric acid (H₂SO₄)
  • Molar mass of H₂SO₄ = 98 g/mol
  • Molarity = 24.5 g / (98 g/mol × 1 L) = 0.25 M
  • Normality = 2 × 0.25 M = 0.5 N (sulfuric acid has two acidic hydrogen atoms)
• Example 3: Calculating molarity from normality - 0.3N H₃PO₄
  • Phosphoric acid (H₃PO₄) has three acidic hydrogen atoms.
  • Molarity = 0.3N / 3 = 0.1 M
• Example 4: Calculating normality from molarity - 3M sulfuric acid
  • Normality = 2 × 3 M = 6N (sulfuric acid has two acidic hydrogen atoms)

Expressions of Concentration

• Molarity - Measures the number of moles of solute per liter of solution.
• Molality - Measures the number of moles of solute per kilogram of solvent.

Ethanol Dilution

• Example: How many milliliters of 70% ethanol are needed to prepare 35 mL of 40% ethanol?
  • Using the formula: V₁C₁ = V₂C₂
  • V₁ = ? (Volume of 70% ethanol)
  • C₁ = 70%
  • V₂ = 35 mL (Final volume)
  • C₂ = 40%
  • V₁ = (V₂C₂) / C₁ = (35 mL × 40%) / 70% = 20 mL
• Therefore, 20 mL of 70% ethanol are needed.

Glassware: Types and Characteristics

• Soft Glass (Boron-free glass)
  • Low thermal resistance (can't be heated)
  • Used for strong acids and alkalis
• Flint Glass (Soda lime glass)
  • Most inexpensive, commonly used for disposables
  • Made from silicon, calcium, and sodium oxides
  • Releases alkali, which can cause errors in some measurements
• Low Actinic Glass (Amber-colored/coated glass)
  • Reduces light transmission
  • Used for photosensitive substances

Pipettes: Air Displacement vs. Positive Displacement

• Air Displacement Pipette:*

• Uses suction to draw sample into a disposable polypropylene tip.

• Piston does not come in contact with liquid (air gap).

• Positive Displacement Pipette:*

• Operates like a hypodermic syringe.

• Piston is in direct contact with the liquid being aspirated.

• Tips are reusable, but must be rinsed out.

• Components: disposable piston, disposable capillary (glass or Teflon), piston seal.

Reagents and Reagent Water

• Copper Reduction Method (for glucose measurement)
  • Based on Benedict's principle: cupric ions are reduced to cuprous ions by glucose in the presence of heat and alkaline environment.
  • Cuprous ions are oxidized by PMA, AMA.
  • Other reducing agents can falsely increase glucose levels.
  • Examples: Foilin-Wu (colorimetric, blue), Nelson Somogyi (colorimetric, blue), Ferricyanide (yellow orange, becomes colorless when reduced).
• Condensation Method (for glucose measurement)
  • Dubowski reaction: intensity of color reaction is proportional to glucose concentration (colorimetric, green)
  • Reaction of glucose with aromatic amines (ortho-toluidine).
• Types of Reagent Water
  • Type I - Most pure, used for critical analysis.
  • Type II - Less pure than Type I, used for general laboratory work.
  • Type III - Least pure, used for rinsing glassware.

Glycemic Control Measures

• Glycosylated Hemoglobin (HbA1c)
  • Hb A with glucose irreversibly attached to one or both N-terminal valines of the β-chains.
  • Provides an index of average blood glucose levels over the past 2-3 months (lifespan of RBCs).
  • Unreliable in patients with hemolytic disorders and hemoglobinopathies (shortened RBC lifespan).
  • Sample: hemolysate (from EDTA whole blood).
  • Methods: Electrophoresis, chromatography, immunoassays.

Enzymatic Methods

• Used for glucose measurement.
• Highly sensitive and specific.

Lipids and Lipoproteins

• Not covered in the provided text.

This quiz covers essential concepts related to SI units and their prefixes, as well as concentration calculations such as molarity and normality. It provides examples and definitions to enhance understanding of these fundamental topics in chemistry.