Stoichiometry

1
Stoichiometry

• Comparing amounts of chemicals in balanced
  equations

2
Finding Mole Ratios
The first thing we must do is to create a
balanced equation for the reaction in question.
Example Sodium hydroxide is mixed with sulfuric
acid in a double replacement reaction.
For every one mole of sulfuric acid reacting,
there has to be 2 moles of sodium hydroxide.
3
Gravimetric Stoichiometry 5-step method
1. Create a balanced chemical equation.
2. List all known and unknown information.
3. Convert the given mass into moles.
4. Find the moles of unknown using the mole
ratio.
5. Calculate the mass of the substance we are
looking for.
4
Gravimetric Stoichiometry
If we decompose 1.00 gram of malachite, how many
grams of copper (II) oxide will be formed?
Octane, C8H18(l), is one of the main constituents
of gasoline. Calculate the mass of carbon
dioxide gas produced by the complete combustion
of 692 g of octane.
5
Solution Stoichiometry
A 10.00 mL sample of sulfuric acid reacts
completely with 15.9 mL of 0.150 mol/L potassium
hydroxide. Calculate the concentration of the
sulfuric acid.
Excess magnesium metal is dropped into 250 mL of
a 0.0350 mol/L solution of hydrochloric acid.
Calculate the mass of hydrogen gas produced by
this reaction.
6
Gas Stoichiometry
Nitrogen and hydrogen gases can be combined to
form ammonia gas. 3.50 moles of hydrogen are
combined with a stoichiometrically equal amount
of nitrogen to produce 50.0 L of ammonia at 80C.
What is the pressure of the ammonia gas formed?
A patron at a lounge, of legal drinking age,
consumes 700 mL of beer with 5 w/v ethanol
content. Calculate the volume of CO2(g) produced
at 37C and 1.00 atm when the ethanol in the beer
is metabolized into burp.
7
Percent Yield/Difference

• Percent yield compares how much chemical was
  produced in an experiment to a prediction (or
  standard).
• yield experimental amount
• predicted amount
• Percent difference shows the deviation of the
  experiment from the prediction.
• difference 100 - yield

8
Limiting Reagent

• The maximum yield that can be achieved in a
  chemical reaction depends on the limiting
  reagent.
• These problems are identified by having two sets
  of given information.
• Compare this information to determine the
  limiting reagent first.

9
Examples

• What volume of hydrogen gas, at STP, will be
  produced when 100 g of aluminium is added to 4.00
  L of 1.40 mol/L sulfuric acid?
• A 6.72 g sample of zinc was placed in 100.0 mL of
  1.50 mol/L hydrochloric acid. Which chemical is
  the limiting reagent? What mass of excess
  reagent is left after the reaction is complete?