Download - I. Stoichiometric Calculations
I. Stoichiometric
Calculations
Stoichiometry
A. Proportional Relationships
I have 5 eggs. How many cookies can I make?
3/4 c. brown sugar
1 tsp vanilla extract
2 eggs
2 c. chocolate chips
Makes 5 dozen cookies.
2 1/4 c. flour
1 tsp. baking soda
1 tsp. salt
1 c. butter
3/4 c. sugar
5 eggs 5 doz.
2 eggs= 12.5 dozen cookies
Ratio of eggs to cookies
A. Proportional Relationships
Stoichiometry
• mass relationships between substances in a chemical reaction
• based on the mole ratio
Mole Ratio
• indicated by coefficients in a balanced equation
2 Mg + O2 2 MgO
B. Stoichiometry Steps
1. Write a balanced equation. Stoichiometry must start with a balance equation
2. Consider which of the following you are trying to do:
• moles moles (1 step)
• moles mass (2 steps)
• mass moles (2 steps)
• mass mass (3 steps)All of them must include moles moles
1 mol of a gas=22.4 Lat STP
C. Molar Volume at STP
Standard Temperature & Pressure0°C and 1 atm
How do I get to moles?
Molar Mass(g/mol)
6.02 1023
particles/mol
MASS
IN
GRAMS
MOLES
NUMBER
OF
PARTICLES
Molar Volume(22.4 L/mol)
LITERS
OF GAS
AT STP
Conversions including molarity
Molar Mass(g/mol)
6.02 1023
particles/mol
MASS
IN
GRAMS
MOLES
NUMBER
OF
PARTICLES
LITERS
OF
SOLUTION
Molar Volume(22.4 L/mol)
LITERS
OF GAS
AT STP
Molarity (mol/L)
Stoichiometry Problems: Moles to MolesIn a spacecraft, the carbon dioxide exhaled by astronauts can be removed by its reaction with lithium hydroxide, LiOH, according to the following chemical equation. How many moles of lithium hydroxide are required to react with 20 molCO2, the average amount exhaled by a person each day?
20 mol CO2 2 mol LiOH
1 mol CO2
= 40 mol
LiOH
? mol20 mol
CO2(g) + 2LiOH(s) → Li2CO3(s) + H2O(l)
Stoichiometry Problems: Moles to MassIn photosynthesis, plants use energy from the sun to produce glucose, C6H12O6, and oxygen from the reaction of carbon dioxide and water. What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide?
3.00
molH2O1 mol C6H12O6
6 mol
H2O
= 90.1 g
C6H12O6
180.2 g C6H12O6
1 mol C6H12O6
3.00 mol ? g
6CO2(g)+6 H2O(l) → C6H12O6(s) + 6O2(g)
Stoichiometry Problems: Mass to MolesThe first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia. If 824 g of NH3 is used in excess oxygen, how manly moles of NO are formed?
824 g NH31 mol
NH3
17.04 g
NH3
= 48.4 mol
NO
4 mol
NO
4 mol
NH3
824 g ? mol
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
Stoichiometry Problems: Mass to MassTin(II) fluoride, SnF2 is used in some toothpastes. It is made by the reaction of tin with hydrogen fluoride according to following equation. How many grams of SnF2 are produced from the reaction of 30.0 g HF with Sn?
30.0
g HF
1 mol
HF
20.01
g HF
= 117.5
g SnF2
Sn(s) + 2HF(g) SnF2(s) + H2(g)
1 mol
SnF2
2 mol
HF
156.7
g SnF2
1 mol
SnF2
30.0 g ? g
Stoichiometry Problems: Converting moles ↔ liters at STP
Add one of the following steps. Can be added to
the equation or done separately.
___ L 1 mol
22.4 L
= ___ mol22.4 L
1 mol
___ mol = ___ L
Stoichiometry Problems: Converting to/from liters at STP
In photosynthesis, plants use energy from the sun to produce glucose, C6H12O6, and oxygen from the reaction of carbon dioxide and water. How much, in liters, oxygen is produced when 3.00 mol of water react with carbon dioxide?
3.00 mol
H2O
6 mol
O2
6 mol
H2O
= 67.2 L O2
22.4 L
O2
1 mol
O2
3.00 mol ? L6CO2(g)+6 H2O(l) → C6H12O6(s) + 6O2(g)