CHEMISTRY

• Factors affecting evaporation rate:

  • Surface area of liquid
  • Temperature
  • Humidity
  • Pressure
• More liquid surface area = faster evaporation rate
• More surface area causes faster evaporation because more molecules are exposed to the air they can escape to.
• Higher temp = faster evaporation
• Higher humidity = slower evaporation
• Higher pressure = slower evaporation
• Humidity introduces more water molecules in the form of vapor.
• Pressure makes it harder for molecules to escape into the air.
• VSEPR = valence shell electron pair repulsion
• VSEPR states that:

  1. valence electrons repulse each other
  2. valence electrons arrange themselves in a way to minimize repulsion and maximize stability
• VSEPR GEOMETRY

  • # of electron dense areas : electron pair geometry
  • 2 : linear
  • 3 : trigonal planar
  • 4 : tetrahedral
  • 5: trigonal biplanar
  • 6 : octahedral
• mole - the amount of substance in a sample equal to 6.02 x 10^23 particles
• Avogadro's number

  6.02 x 10^23 particles = 1 mole
• Formula mass - ionic compounds

  Molecular mass - covalent compounds
• ionic = metal + nonmetal

  covalent = nonmetal + nonmetal or metalloid
• formula or molecular mass - sum of atomic masses of each atom in a chemical equation
• molar mass - mass of 1 mole of substance
• molar mass = grams/mole
• Moles to grams

  mole x (g/mol) = g
• Mass to moles

  g x (1/mol) = moles
• Particles to moles

  P x (1 mol/Avogadro's) = moles
• Moles to particles

  Moles x (Avogadro's/1 mol) = P
• % composition of elements in a compound =

  (mass of element ÷ mass of compound) x 100%
• To check mole ratio, look at the coefficients.
• solution = solute + solvent
• solute is dissolved in solvent
• solvent is what solute is dissolved in
• Molarity is the amount of solute per unit volume of solution.
• Molarity formula

  M = # of moles/Liters of solvent
• Molality is the amount of solute per unit mass of solvent.
• Molality formula

  mol/kg = # of moles/kg
• Molarity is based on volume. Molality is based on mass.
• Molarity is affected by temperature. Molality is not affected by temperature.
• pH = -log[H₃O⁺]
• pH Levels:

  0-6: acid

  7: neutral

  8-14: base
• Acid and Bases Theories:

  1. Arrhenius
  2. Bronsted-Lowry
  3. Lewis
• Properties of acids:

  1. A: produces H+ (hydrogen ion)
  2. B-L: proton donor
  3. L: electron pair acceptor
• Properties of bases:

  1. A: produces OH- (hydroxide)
  2. B-L: proton acceptor
  3. L: electron pair donor
• The Bronsted-Lowry theory states that acids and bases exchange protons to form new conjugate acids and bases.
• Conjugate acids and bases:

  • conjugate acid = base + proton
  • conjugate base = acid - proton