9.3 NOTES Stoichiometry Non- Mass – Mass Problems
B. Non-mass-mass calculations These problems involve moles and/or grams in some combination. These problems have fewer fractions than the normal mass-mass problems.
a. Example: If 12.8 grams of lithium are reacted with oxygen gas, how many moles of lithium oxide are formed? 4Li + O2 2Li2O Given: 12.8g Li (6.94g/mol) Find: moles Li2O 12.8 g Li x 1 mol Li x 2 mol Li2O 6.94 g Li 4 mol Li = 0.922 mol Li2O
b. If 0.45 mole of water is decomposed, how many moles of oxygen gas are produced? 2H2O 2H2 + O2 Given: 0.45 mol H2O Find: moles O2 0.45 mol H2O x 1 mol O2 2 mol H2O = 0.23 mol O2