1. U NIT 8: M EASUREMENTS AND C ALCULATIONS IN CHEMISTRY – S TOICHIOMETRY I Dr. Chin Chu Chemistry River Dell High School

2. C HEMICAL R EACTIONS Nitrogen gas reacts with hydrogen gas to form ammonia gas.

3. C HEMICAL REACTIONS

4. STOICHIOMETRY Definition – a branch of chemistry that deals with the relative quantities of reactants and products in chemical reactions.

5. S TOICHIOMETRY – EXERCISE PROBLEMS What are the mole ratios for the balanced chemical reaction: CH 4 + 2O 2  CO 2 + 2H 2 O? What are the mole ratios for the chemical reaction: element phosphorus reacts with oxygen gas to form diphosphorus pentoxide? 2Ag 2 O  4Ag + O 2, how many moles of metallic silver and oxygen gas will be produced when 3.27 moles of silver oxide are completely decomposed? The balanced chemical equation for a double- replacement reaction is: FeCl 3 (aq) + 3NaOH(aq)  Fe(OH) 3 (p) + 3NaCl(aq). What are the moles of each reactant needed to produce 2.68 moles of Fe(OH) 3 precipitate?

6. S TOICHIOMETRY – ANSWERS What are the mole ratios for the balanced chemical reaction: CH 4 + 2O 2  CO 2 + 2H 2 O? [1 mol(CH 4 ) = 2 mol(O 2 ) = 1 mol(CO 2 ) = 2 mol(H 2 O)] What are the mole ratios for the chemical reaction: element phosphorus reacts with oxygen gas to form diphosphorus pentoxide? [4P + 5O 2  2P 2 O 5, 4 mol(P) = 5 mol(O 2 ) = 2 mol(P 2 O 5 )] 2Ag 2 O  4Ag + O 2, how many moles of metallic silver and oxygen gas will be produced when 3.27 moles of silver oxide are completely decomposed? [Ag: 6.54 mol; O 2 : 1.64 mol] The balanced chemical equation for a double-replacement reaction is: FeCl 3 (aq) + 3NaOH(aq)  Fe(OH) 3 (p) + 3NaCl(aq). What are the moles of each reactant needed to produce 2.68 moles of Fe(OH) 3 precipitate? [FeCl3: 2.68 mol, NaOH: 8.04 mol]