Stoichiometry Compostion Stoichiometry- Mass relationship of elements in compounds Reaction Stoichiometry- Mass relationship between reactants and products in a chemical reaction.

Key Parts to Stoichiometry: 1) The Equation must ALWAYS be balanced first! 2) You must be able to correctly identify the mole ratio needed for proper computation. Mole Ratio = a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction. 3) Determine the Molar Masses of each substance involved in the computation. 1) The Equation must ALWAYS be balanced first! 2) You must be able to correctly identify the mole ratio needed for proper computation. Mole Ratio = a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction. 3) Determine the Molar Masses of each substance involved in the computation.

StoichiometryStoichiometry 1) List all of the mole ratios: 2) In other words, this tells us that for every 4 moles of NH 3, 5 moles of O 2 are required, 6 moles of H 2 O form with 4 moles of NO. 3)Recall also that molar masses provide conversion factors: 1 mol NH 3 / g NH 3, g O 2 / 1 mol O 2 1) List all of the mole ratios: 2) In other words, this tells us that for every 4 moles of NH 3, 5 moles of O 2 are required, 6 moles of H 2 O form with 4 moles of NO. 3)Recall also that molar masses provide conversion factors: 1 mol NH 3 / g NH 3, g O 2 / 1 mol O 2 Consider: 4NH 3 + 5O 2  6H 2 O + 4NO

How many moles of H 2 O are produced if mol of O 2 are used?  How many moles of NO are produced in the reaction if 17 mol of H 2 O are also produced? Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many moles of H 2 O are produced if mol of O 2 are used?  How many moles of NO are produced in the reaction if 17 mol of H 2 O are also produced? 6 mol H 2 O 5 mol O 2 x Stoichiometry questions (mol -> mol) # mol H 2 O=0.176 mol O mol H 2 O = 4 mol NO 6 mol H 2 O x # mol NO=17 mol H 2 O mol NO = Notice that a correctly balanced equation is essential to get the right answer

Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of H 2 O are produced if mol of O 2 are used?  How many grams of NO are produced in the reaction if 17 mol of H 2 O are also produced? Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of H 2 O are produced if mol of O 2 are used?  How many grams of NO are produced in the reaction if 17 mol of H 2 O are also produced? 6 mol H 2 O 5 mol O 2 x Stoichiometry questions (mol -> mass) # g H 2 O= mol O g H 2 O = 4 mol NO 6 mol H 2 O x # g NO= 17 mol H 2 O g NO = Notice that a correctly balanced equation is essential to get the right answer g NO 1 mol NO x g H 2 O 1 mol H 2 O x

Consider : 4NH 3 + 5O 2  6H 2 O + 4NO  How many grams of H 2 O are produced if 1.9 mol of NH 3 are combined with excess oxygen?  How many grams of O 2 are required to produce 0.3 mol of H 2 O? Consider : 4NH 3 + 5O 2  6H 2 O + 4NO  How many grams of H 2 O are produced if 1.9 mol of NH 3 are combined with excess oxygen?  How many grams of O 2 are required to produce 0.3 mol of H 2 O? 6 mol H 2 O 4 mol NH 3 x Stoichiometry questions (practice) # g H 2 O= 1.9 mol NH g H 2 O = g H 2 O 1 mol H 2 O x 5 mol O 2 6 mol H 2 O x # g O 2 = 0.3 mol H 2 O 8 g O 2 = 32 g O 2 1 mol O 2 x

Consider : 4NH 3 + 5O 2  6H 2 O + 4NO  How many moles of H 2 O are produced if 49 grams of NH 3 are reacted?  How many moles of O 2 are required to produce 200 g of H 2 O? Consider : 4NH 3 + 5O 2  6H 2 O + 4NO  How many moles of H 2 O are produced if 49 grams of NH 3 are reacted?  How many moles of O 2 are required to produce 200 g of H 2 O? 1 mol NH 3 17 g NH 3 x Stoichiometry questions (mass -> mol) # mol H 2 O= 49 g NH mol H 2 O = 6 mol H 2 O 4 mol NH 3 x 1 mol H 2 O g H 2 O x # mol O 2 = 200 g H 2 O mol O 2 = 5 mol O 2 1 mol H 2 O x

Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of NO is produced if 12 g of O 2 is combined with excess ammonia? Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of NO is produced if 12 g of O 2 is combined with excess ammonia? 4 mol NO 5 mol O 2 x Stoichiometry questions (mass -> mass) # g NO= 12 g O g NO= g NO 1 mol NO x 1 mol O 2 32 g O 2 x

 Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles.  Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y)  We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following  Given 2 moles H 2 O, calculate grams H 2 O?  Moles O 2 required for 36 g H 2 ?  Grams of H 2 O produced from 6 grams O 2 ?  Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles.  Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y)  We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following  Given 2 moles H 2 O, calculate grams H 2 O?  Moles O 2 required for 36 g H 2 ?  Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Converting grams to grams

Moving along the stoichiometry path  We always use the same type of information to make the jumps between steps: grams (x)  moles (x)  moles (y)  grams (y)  We always use the same type of information to make the jumps between steps: grams (x)  moles (x)  moles (y)  grams (y) Molar mass of xMolar mass of y Mole ratio from balanced equation Given: 4NH 3 + 5O 2  6H 2 O + 4NO a) How many moles of H 2 O can be made using 0.5 mol NH 3 ? b) what mass of NH 3 is needed to make 1.5 mol NO? c) how many grams of NO can be made from 120 g of NH 3 ?

4NH 3 + 5O 2  6H 2 O + 4NO a) b) c) 4NH 3 + 5O 2  6H 2 O + 4NO a) b) c) Answers 6 mol H 2 O 4 mol NH 3 x # mol H 2 O=0.5 mol NH mol H 2 O = 4 mol NH 3 4 mol NO x # g NH 3 = 1.5 mol NO 25.6 g NH 3 = g NH 3 1 mol NH 3 x 4 mol NO 4 mol NH 3 x # g NO= 120 g NH g NO= g NO 1 mol NO x 1 mol NH g NH 3 x