Chemistry
Notes- Stoichiometry and Limiting Reactants
Name: ___________________________________
Date: ______________ Block: ________________
Key Things to remember about DA:
Mole Ratios:
AgNO3 (aq) + NaCl(aq)  AgCl(aq) + NaNO3 (aq)
If 1 mole of AgNO3 reacts, ____ moles of NaCl are needed, ____ moles of AgCl and ___ moles of NaNO3 are formed.
Thus if 2 moles of AgNO3 react, ____ moles of NaCl are needed, ____ moles of AgCl and ___ moles of NaNO3 are formed.
2 H2 (g) + O2 (g)  2 H2O (g)
If 2 mole of H2 react, ____ moles of O2 are needed, ____ moles of H2O are formed.
If 4 mole of H2 react, ____ moles of O2 are needed, ____ moles of H2O are formed.
3 Step Mole Method…
Step 1: Convert given to Moles of “given” (A)
Step 2: Convert moles of “given” (A) to moles of “find” (B)
Step 3: Convert moles of “find” (B) to grams of “find” (B)
Conversion Flow Map:
How to think about a stoichiometry problem…
C2H5OH + 3 O2  2 CO2 + 3 H2O
The Problem: Find the number of grams of oxygen gas needed to burn 2.30 grams of C2H5OH.
1. OUTLINE THE PROBLEM – indicate the substance and units
GIVEN (A):___________________________________
FIND (B):____________________________________
2. ANALYZE THE PROBLEM – How many steps of the 3 step mole method are needed?
STEP I (Y or N)
STEP II (Y or N)
STEP III (Y or N)
3. SET UP THE UNIT FACTORS - Flow the flow map and use DA to cross out units.
Find the number of grams of oxygen gas needed to burn 2.30 grams of C2H5OH
C2H5OH + 3 O2  2 CO2 + 3 H2O
How many moles of oxygen are needed to completely combust 50.0 g ethanol?
C2H5OH + 3 O2  2 CO2 + 3 H2O
How many grams of CO2 will be produced if 12.0 grams of oxygen react?
C2H5OH + 3 O2  2 CO2 + 3 H2O
How many grams of ethanol would be needed to produce 35.0 grams of carbon dioxide?
C2H5OH + 3 O2  2 CO2 + 3 H2O
Limiting Reactants
Limiting Reactants
Balanced Chemical Equation:
The __________ to understanding ___________________
is to understand the meaning of a ___________ chemical
equation.
Brownie Recipe:
Ammonia Recipe
N2 (g) + 3 H2 (g)  2 NH3 (g)
This _____________ equation tell you the ____________ in which the _____________ react.
_________ how __________ you have/make of each!!!
Limiting Reactant Definition:
Steps to figure out limiting reactants:
Excess Reactant Definition:
If you have 3 moles NaOH and 4 moles of HCl…What’s your limiting reactant?
_____NaOH (aq) + _____HCl (aq)  _____H2O (l) + _____NaCl (aq)
If you have 3 moles NaOH and 4 moles of HCl… How many moles of product will be formed?
_____NaOH (aq) + _____HCl (aq)  _____H2O (l) + _____NaCl (aq)
If you have 5 moles silver nitrate and 3 moles of barium chloride…What’s your limiting reactant?
____AgNO3 (aq) +____BaCl2 (g)  ____ AgCl (s) + ____Ba(NO3)2 (aq)
Finding Excess Reactants:
If you have 5 moles silver nitrate and 3 moles of barium chloride… how much excess reactant will be left over?
____AgNO3 (aq) +____BaCl2 (g)  ____ AgCl (s) + ____Ba(NO3)2 (aq)
If you have 2.5 moles of nitrogen and 6 moles of hydrogen….How much excess reactant will be left over?
______N2 (g) + ______H2 (g)  _____NH3 (g)
Percent Yield
Practice Problem:
Percent Error