STOICHIOMETRY
STEPS
STEPS
What is the first step you take when doing stoichiometry?
Balance the chemical equation.
What do you use to convert from moles of one substance to moles of another substance?
The Molar Ratio.
What is Stoichiometry?
The study of quantities of materials consumed and produced in chemical reactions
Given the following balanced equation, determine how many moles of Fe2O3 will form from 5.0 moles of Fe?
4Fe + 3O2 --> 2Fe2O3
2.5 moles of Fe
A student is trying to figure out how many moles of MgO she will produce when mixing 2.40 g Mg with 10.0 g O2.
Based off of her work, which compound (Mg or O2) is the limiting reactant?
Mg
What is the second step you take in stoichiometry?
Identify your 'known' and 'unknown' information
4Fe + 3O2 --> 2Fe2O3
What is the mole ratio of Iron to Oxygen gas?
4:3
What do we look at to find molar ratios?
The coefficients in a balanced equation.
2KClO3 --> 2KCL + 3O2
How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas?
6 moles of KClO3
Theoretically, 49.5 g of CO2 would be produced if 20g of Propane reacts with 60g of Oxygen gas.
Cars actually only emit 39.6 g CO2 from the same reaction. Calculate the percent yield.
80%
What is the third step you take in stoichiometry?
Set up conversion factors
What piece of information do you need to convert from moles to grams of a substance?
The Molar Mass.
Which type of calculation would I perform if I wanted to determine how many grams of Cu I would obtain from mixing 1.00g Zn with excess CuSO4?
A 3-step calculation
Cl2 + 2Na --> 2NaCl
How many grams of NaCl will be produced from 1.25 mol of chlorine gas reacting with sodium?
146 g NaCl
Given the following reaction, how many grams of Ag will be produced from 5.00g of Cu and 1.00g of AgNO3?
Cu + 2AgNO3 --> 2Ag + Cu(NO3)2
0.635 g Ag
How does one figure out the limiting reactant?
Perform a 3-step (mass to mass) calculation for each reactant in a reaction.
The one that produces the least product is the limiting reactant.
Calculate the molar mass of Acetaminophen (C8H9NO2), known commercially as Tylenol.
151.163 g/mol
What is Excess Reactant?
Reactant that is not used up when a reaction is run to completion.
Fe3O4 + 4 CO -->3 Fe + 4 CO2
How many moles of CO are needed to react with 16.5 g of Fe3O4?
0.285 moles CO
4NH3 + 5O2 –> 4NO + 6H2O
In an experiment, 6.50 g of NH3 was allowed to react with 7.00 g of O2.
How much excess reactant remains after the reaction?
3.52 g NH3
How does one calculate the amount of excess reactant remaining after a chemical reaction has occurred to completion?
Find the theoretical yield.
Use the theoretical yield and set up a 3-step calculation to find the amount (in grams) of excess reactant used.
Subtract the amount of excess reactant used from the original amount of excess reactant to find how much excess reactant remains after the reaction occurs.
Cu + 4HNO3 –> Cu(NO3)2 + 2NO2 + 2H2O Set up the 3-step calculation for determining how many grams of HNO3 is need to produce 6.97g of Cu(NO3)2.
6.97g Cu(NO3)2 x 1 mol/187.56 x 4 mol/1 mol x 63.01g/1 mol HNO3
What is the difference between theoretical yield and actual yield?
Theoretical yield: the maximum amount of a product that can be formed with the limiting reactant
Actual yield: the actual amount of a product that is formed when carrying out the reaction in a lab setting
Ammonium nitrate decomposes into dinitrogen monoxide gas and water, as seen in the following unbalanced chemical equation:
NH4NO3 → N2O + H2O
Determine the amount, in grams, of water produced if 25.0 g of ammonium nitrate decomposes.
11.3 g H2O
4Al + 3O2 –> 2Al2O3
Identify the limiting reactant for each scenarios:
0.225 mol Al reacts with 0.415 mol O2
77.9 g Al reacts with 111.9 g O2
58.7 g Al reacts with 54.1 g O2
a. Al b. Al c. Al