empirical and molecuar formula

• What does the empirical formula represent?

  It shows the simplest whole number ratio of atoms
• What does the molecular formula indicate?

  It gives the actual number and type of atoms
• How can empirical formulas be derived from combustion reactions?

  By determining moles of products and inferring original moles
• What are the steps to derive empirical formulas from combustion products?

  1. Determine moles of products using mass and molar mass
  2. Infer moles of each element in the original compound
  3. Simplify to the lowest mole ratio
  4. Derive the empirical formula from this ratio
• What do ionic compounds consist of?

  A lattice of alternating positive and negative ions
• What is water of crystallisation in ionic compounds?

  Water molecules lodged within the lattice framework
• What is anhydrous ionic compound?

  An ionic compound without water of crystallisation
• What is a hydrated ionic compound?

  An ionic compound with water of crystallisation
• How do anhydrous and hydrated forms of the same compound differ visually?

  They often have different colors
• What is the color of anhydrous copper sulfate?

  White
• What is the color of hydrated copper sulfate?

  Blue
• How is a hydrated compound denoted in its formula?

  With a dot separating salt and water molecules
• What is the formula for copper sulfate pentahydrate?

  CuSO4•5H2O
• What is the procedure to experimentally determine the formula of a hydrated ionic compound?

  1. Heat the hydrated salt to remove water
  2. Calculate moles of water lost and anhydrous salt remaining
  3. Find the mole ratio of salt to water
  4. Express this ratio as a whole number in the formula
• What happens to a hydrated salt when heated?

  It loses water and becomes anhydrous
• How do you find the mole ratio of salt to water after heating a hydrated compound?

  By calculating moles of water lost and remaining salt
• Why is it useful to assume a total sample size of 100 g when calculating empirical formulas?

  It simplifies calculations as percentages equal grams