CALCULATION ANACHEM

• The mole (mol) is the SI unit for the amount of a chemical species
• The mole is always associated with a chemical formula and represents Avogadro’s number (6.022 × 10^23) of particles represented by that formula
• The molar mass (M) of a substance is the mass in grams of one mole of the substance
• Molar masses are calculated by summing the atomic masses of all elements appearing in a chemical formula
• Example: Calculate the molar mass of formaldehyde (CH2O)

  • C: 12.0 g
  • H: 1.0 g
  • O: 16.0 g
  • M (CH2O) = 12 + 2 + 16 = 30 g/mol
• Sometimes it is more convenient to make calculations with millimoles (mmol) rather than moles, where 1 mmol is 1/1000 of a mole
• 1 mmol = 10^-3 mol

  1 mol = 1000 mmol
• Example: Determine the number of moles and millimoles of benzoic acid (C7H6O2) in 2.00 grams of the pure acid

  • M (C7H6O2) = 122 g/mol
• Mass is an invariant measure of the amount of matter in an object, while weight is the force of attraction between an object and its surroundings
• Weight and mass are related by the expression: W = mg, where W is the weight of the object, m is the mass of the object, and g is the acceleration due to gravity
• Analytical molarity gives the total number of moles of a solute in 1 L of the solution
• Equilibrium molarity expresses the molar concentration of a particular species in a solution at equilibrium
• Normality (N) is a term of concentration based on the ability of some substances to release hydrogen (H+) or hydroxide (OH-) ions in solution
• Normality can be determined given the weight of solute and the volume of solution using the equation N = Eq/L
• Example: What is the normality of a 1-L solution containing 46.3 g Ca(OH)2? (MW of Ca(OH)2 = 74.1 g/mol)

  • The normality of this solution can be written as 1.25 N or 1.25 Eq/L
• Chemists frequently express concentrations in terms of percent (parts per hundred)
• Density is the mass of a substance per unit volume, expressed in units of kg/L or g/mL in SI units
• Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water