Decomposition of Baking Soda
*Now try problems #1 and 2 on page 8*
*Now try problems #3 and 4 on page 8*
*Now try problems #5 and 6 on page 9*
Stoichiometry II Practice Problems
1. How many grams of H2O are produced when 2.50 grams of oxygen are used?
H2 + O2 ( H2O
2. If 89.5 grams of Ag were produced, how many grams of Cu reacted?
Cu + AgNO3 ( Cu(NO3)2 + Ag
3. What mass of ammonia is formed when 5.38 moles of lithium nitride reacts with water?
Li3N + H2O ( NH3 + Li2O
4. How many grams of KCl are produced from 2.50 mol of K and excess Cl2?
K + Cl2 ( KCl
5. If 80.0 grams of O2 were produced, how many moles of KClO3 decomposed?
KClO3 ( KCl + O2
6. How many moles of sodium iodide will completely react with 10.3 grams of bromine?
Br2 + NaI ( NaBr + I2
7. Molten iron and carbon monoxide are produced in a blast furnace by reacting iron (III) oxide and pure carbon. If 25.0 grams of pure iron (III) oxide is used, how many grams of iron can be produced?
Fe2O3 + 3 C ( 2 Fe + 3 CO
8. The average human requires 120.0 grams of glucose (C6H12O6) per day. How many grams of carbon dioxide (in the photosynthesis reaction) are produced from this amount of glucose?
C6H12O6 + 6 O2 ( 6 CO2 + 6 H2O
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How to do Mass-Mole Problems
You are given the mass, in grams, of one substance and asked to find the number of moles of another substance.
Steps: 1. Write correct formulas
2. Balance the equation
3. Convert the mass given into moles (divide by molar mass)
4. Multiply by the correct mole ratio.
Example : How many moles of FeO will be produced if 50.0 grams of Fe are reacted with excess oxygen?
Fe + O2 ( FeO
How to do Mole-Mass Problems
You are given the number of moles of one substance and asked to find the mass, in grams, of another substance. Steps: 1. Write correct formulas
2. Balance the equation
3. Multiply the moles given by the correct mole ratio.
4. Convert the moles into mass (multiply by molar mass)
Example : How many grams of FeO will be produced from 20.8 moles of oxygen and excess iron?
Fe + O2 ( FeO
[pic]
How to do Mass-Mass Problems (Most Common)
You are given the mass of one substance and asked to find the mass, in grams, of another substance.
Steps: 1. Write correct formulas
2. Balance the equation
3. Convert the mass into moles (divide by molar mass)
4. Multiply by the correct mole ratio.
5. Convert the moles into mass (multiply by molar mass)
Example 1: How many grams of iron will react with 8.80 grams of oxygen?
Fe + O2 ( FeO
Example 2: How many grams of FeO will be produced from 8.80 grams of oxygen and excess iron?
[pic]
Step 2:
Use mole ratio (mole bridge) to convert between two chemicals
Step 3:
Convert to desired units of second chemical
Step 1:
Find moles of first chemical
Solving Stoichiometry problems--Up to three steps!
"That which you persist in doing becomes easy to do - not that the nature of the thing has changed, but your power and ability to do has increased." -- H.J. Grant
Remember…
All stoichiometry problems start with
correct formulas and a balanced equation!
Stoichiometry II: Mass to Mass
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