Name ____________________________________
Period ____________
9-1 Stoichiometry & Balanced Chemical Reactions
1. How do balanced chemical reactions relate to moles?
2H2
+
O2
→
2H2O
2. You can interpret the above balanced chemical reaction in a number of ways
a. If equation is interpreted in terms of particles:
i. 2 molecules of H2 react with 1 molecule of O2 to produce 2 molecules H2O of water.
1. The ratio of H2 to O2 to H2O is 2 : 1 : 2.
Or
ii. 20 molecules of H2 react with 10 molecules of O2 to produce 20 molecules of water.
1. The ratio of H2 to O2 to H2O is 2:1:2.
Or
iii. 2 x the molecules of H2 react with 1x the molecules of O2 to produce 2x molecules of water.
1. No matter what x is the ratio of H2 to O2 to H2O is still 2 : 1 : 2.
How many molecule of water would be produced if 6
molecules of H2 react with excess O2?
How many molecule of water would be produced if 6
molecules of O2 react with excess H2?
How many molecule of water would be produced if 6736
molecules of H2 react with excess O2?
How many molecule of water would be produced if 1 mole
of H2 molecules react with excess O2?
It is more convenient to interpret the coefficients as the number of moles, because we measure amounts of substances
by mass in the laboratory. We can convert between grams and moles in solving problems involving chemical reactions.
1. What is Stoichiometry?
a. Stoichiometry - The study of the molecular ratios that exist in a balanced formula chemical reactions.
i. Stoichiometry makes it possible to manufacture chemicals and pharmaceuticals safe and
economical.
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2.
How do you solve a Stoichiometry problem?
a. Mole-Mole Problems require 3 steps to solve
i. Write the balanced chemical equation
ii. Determine the molar ratio
iii. Use dimensional analysis to solve
Ammonium nitrate decomposes into dinitrogen monoxide and water. How many moles of products are produced from
2.25 moles of reactants?
Equation:
Ratio:
Hydrochloric acid reacts with zinc to form zinc chloride and hydrogen gas. How many moles of HCl are needed to react
with 2.3 moles of Zn?
Equation:
Ratio:
Name ____________________________________
Period ____________
9-2 Stoichiometry
1. How do you solve a Stoichiometry problem?
a.
b.
2
c.
d.
e.
Al
+
O2
→
Al2O3
1. What mass of Al2O3 can be prepared by the reaction of 67.5 g of Al according to the equation below?
Mole Ratio:__________________
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2. What volume of O2 gas can be obtained from reacting 100g of Al?
Mole Ratio:__________________
3. How many atoms of Al2O3 would you get from reacting 67L of O2 at STP?
Mole Ratio:__________________
4. How many moles of Al2O3 would you get from reacting 20g of Al?
Mole Ratio:__________________
5. What mass of O2 would you need to start with to obtain 1Kg of Al2O3?
Mole Ratio:__________________
9-3
% Composition
1) What is a percent?
2) How are percents represented?
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3) What is percent composition?
a) % Composition –
4) How is percent composition calculated?
Example using molar mass) What is the % hydrogen in water?
Example using grams of each element in the compound: Find the % composition of a compound that contains 2.30
g of sodium, 1.60 g of oxygen, and 0.100 g of hydrogen.
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