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Stoichiometry. Lancaster High School. Stoichiometry. “ stochio ” = ___________ “ metry ” = ____________ Stoichiometry is about measuring the amounts of elements and compounds involved in a reaction. Consider the chemical equation: 4NH 3 + 5O 2 6H 2 O + 4NO
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Stoichiometry Lancaster High School
Stoichiometry “stochio” = ___________ “metry” = ____________ Stoichiometry is about measuring the amounts of elements and compounds involved in a reaction. Consider the chemical equation: 4NH3 + 5O2 6H2O + 4NO There are several numbers involved. What do they all mean?
Stoichiometry 4NH3 + 5O2 6H2O + 4NO Recall that Chemical formulas represent numbers of atoms
Stoichiometry 4NH3 + 5O2 6H2O + 4NO Recall that Chemical formulas have molar masses:
4NH3 + 5O2 6H2O + 4NO Stoichiometry Recall that Chemical formulas are balanced with coefficients
Stoichiometry 4NH3 + 5O2 6H2O + 4NO With Stoichiometry we find out that 4 : 5 : 6 : 4 do more than just multiply atoms. 4 : 5 : 6 : 4 Are what we call a ____ ratio.
Stoichiometry 4NH3 + 5O2 6H2O + 4NO 4 : 5 : 6 : 4 Can mean either: 4 _________ of NH3 react with 5 _________ of O2 to produce 6 __________ of H2O and 4 _________ of NO OR 4 ______ of NH3 react with 5 ______ of O2 to produce 6 ______ of H2O and 4 ______ of NO
Stoichiometry Question (1) 4NH3 + 5O2 6H2O + 4NO • How many moles of H2O are produced if 2.00 moles of O2 are used? Notice that a correctly __________ equation is essential to get the right answer
Stoichiometry Question (2) 4 NH3 + 5 O2 6 H2O + 4 NO How many moles of NO are produced in the reaction if 15 mol of H2O are also produced?
Stoichiometry Question (3) 4 NH3 + 5 O2 6 H2O + 4 NO • How many grams of H2O are produced if 2.2 mol of NH3 are combined with excess oxygen?
Stoichiometry Question (4) 4 NH3 + 5 O2 6 H2O + 4 NO • How many grams of O2 are required to produce 0.3 mol of H2O?
Stoichiometry Question (5) 4 NH3 + 5 O2 6 H2O + 4 NO • How many grams of NO is produced if 12 g of O2 is combined with excess ammonia?
_______of x _________of y _____ ratio from ________________ 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)
Converting grams to grams 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 Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles and mole ratio in the balanced equation.
Have we learned it yet? Try these on your own - 4 NH3 + 5 O2 6 H2O + 4 NO a) How many moles of H2O can be made using 1.6 mol NH3? b) what mass of NH3 is needed to make 0.75 mol NO? c) how many grams of NO can be made from 47 g of NH3?