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Stoichiometry Worksheet
Example:
The formation of water from hydrogen and oxygen gas is: 2H2 (g) + O2 (g) --->
2H2O (l). What mass of water will form from 12.0 grams of hydrogen and excess
oxygen (assuming the reaction goes to completion?)
Answer
First what you must do in any of these problems is get all given masses into
moles. You are given 12.0 grams of hydrogen, let's see how many moles that is:
12.0 g H2 x 1 mol / 2.02 g = 5.94 mol H2
So how much water is formed? According to the equation, for every 2 moles of
hydrogen, 2 moles of water are produced, or in other words, a 1 to 1 ratio. So 5.94
moles of water will be formed. The question asks for what mass, so we're not
quite done yet.
5.94 mol H2O x 18.0 g / mol = 107. grams of H2O.
1. How much water could you produce if you were only given 8.0 g of
hydrogen?
2. If you had 12 g of hydrogen and 100 g of oxygen, which one is the limiting
reagent (limiting reactant)?
3. How much water was produced from problem 2?
4. If 0.2 kg of water is produced, how much oxygen was used?
5. If 0.2 kg of water is produced, how much hydrogen was used?
The reaction that propels rockets is based on the reaction of hydrazine (N2H4).
Assume that you have 1200 kg of N2H4 and that it is completely used up by the
reaction.
N2H4 +
(CH3)2N2H2 +
N2O →
N2 +
CO2 +
H2O
6. Balance the above formula
7. What is the mole ratio of N2H4 to (CH3)2N2H2?_________
8. How much (CH3)2N2H2 is needed?
9. What is the mole ratio of N2H4 to H2O?_________
10. How much H2O is produced?
The reaction that causes cake batter to rise involves the production of CO2 from
NaHCO3 (Sodium Bicarbonate, also known as baking soda). Assume that you
started with 15.0 g of NaHCO3 and heated it up to make the reaction happen.
NaHCO3
→
Na2CO3 +
H2O + CO2
11. Balance the above formula
12. What is the mole ratio of NaHCO3 to CO2? _________
13. How much CO2 is produced?
14. How many liters of CO2 gas will be created? Note: at baking temperature
the density of CO2 gas is 1.10 g/L.
15. What type of reaction is this?