ch 3

Question 1

molar mass name for ionic compounds

Answer 1

formula weight

Question 2

molar mass name for covalent compounds

Answer 2

molecular weight

Question 3

finding emp form using mass %s

Answer 3

• assume 100 g
• convert % to grams of sample in 100 g
• convert g to moles
• divide by the smallest number of moles

Question 4

finding emp form through combustion analysis

Answer 4

• Given amount of CO2 formed, convert to moles of carbon or grams of carbon (C).
• Given amount of H2O formed, convert to moles of hydrogen or grams of hydrogen (H).
• If nitrogen is in your original sample also, given amount of N2 formed, convert to moles of nitrogen or grams of nitrogen (N).
• If oxygen is in your original sample, determine the amount of oxygen in your sample by subtracting the initial amount of sample given by the carbon, hydrogen, and nitrogen from steps 1-3.
• Once you have moles of all elements in your original sample, follow simple directions for determining empirical formula (divide all by the smallest number of moles, this is the mole ratio of all the elements in your sample, the empirical formula)!

Question 5

finding molecular formula from empirical formula

Answer 5

divide molecular formula’s molar mass by the empirical formulas molar mass