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Stoichiometry Unit Study Guide Part 1
Part A: Molar Mass
Molar mass tells us the mass (“weight”) of 1 mol ofan atom or compound. In each case we simply
calculate the sum of the “weights” of the atoms in the formula to determine the weight of a mole.
These weights can be found on the periodic table.
EXAMPLE: Calculate the molar mass (gram molecular weight) of a mole of iodine, I 2. Round to 2
decimal places.
2 I = 2 X (126.90) = 253.80 g I2/mol
EXAMPLE: Calculate the molar mass (gram formula weight) of a mole of aluminum sulfate, Al 2(SO4)3.
Round to 2 decimal places.
2 Al = 2 X (26.98) = 53. 96
3 S = 3 X (32.07) = 64.14
+ 12 O = 12 X (16.00) = 192.00
__________________________________________
Al2(SO4)3
= 310.10 g Al2(SO4)3 /mol
Calculate the molar mass of the following compounds. Show work and write in units of
grams/mol.
1. Water H2O
____________________
2. calcium chloride CaCl2 ____________________
3.
copper(II) sulfate
CuSO4
____________________
4. silver nitrate AgNO
3 ____________________
5. sulfuric acid
H2SO4. ____________________
Part B: 1 Step Molar Conversons
Fill in the graphic organizer below
Complete the following 1-step conversions.
What is the volume, in liters, of 0.250
moles of carbon monoxide CO at STP?
How many moles of chlorine are there in a
67.2 liter sample of chlorine Cl2 at STP?
Part C: 2 Step Molar Conversons
Complete the following conversions
1) How
2)
many molecules are there in 345 grams of carbon dioxide CO2?
24
What would be the mass, in grams, of 1.204 x 10 molecules of sulfur dioxide SO2?
3
3) How many molecules of water are there in 8.050 x 10 grams of water H2O?
4)
How many oxygen molecules are in a flask that contains 1.43 grams of oxygen O2?
5) What would be the mass, in grams, of 45.0 liters of nitrogen N2 at STP?
6) How many molecules of hydrogen H2 are in a balloon full of hydrogen with a volume of 5.34 liters at STP?
Part D: Limiting Reagent
Define the following terms
a – Limiting Reagent
b – Excess Reactant
Describe these terms in context of either our schmores lab or our copper chloride lab.
Part E: Mole Ratios
Given the equation
N2 + 3H2 → 2NH3
, Give the mole ratios
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐻2
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁𝐻3
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐻2
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁2
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁2
𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑁𝐻3
Part F: Mole Ratios – Mole to Mole 1 Step Conversions
1) Suppose you had 15 moles of H2 , how many moles of ammonia would you make?
2) Suppose you had 10 moles of ammonia, how many moles of nitrogen did you use to make it?
3) Consider the combustion of methane:
How many moles methane (CH4) would be needed to produce 18 moles of water?
Part G: Mole Ratios – Gram to Gram
3 Step
Conversions
Step 1: Convert from Grams A to Moles A Using __________________
Step 2: Convert from Moles A to Moles B Using ___________________
Step 3: Convert from Moles B to Grams B Using __________________
Given the equation…2H2 +
O2 → 2H2O
1) If you used 64 grams of oxygen, how many grams of water would you produce?
2) If you used 10g of Hydrogen (H2), how many grams of oxygen would you need to complete
react?
3) If you produced 54 grams of water, how many grams of hydrogen (H2) did you need to use?
Given the equation…
N2 + 3H2 → 2NH3
4) If you used 155.0 g of Nitrogen (N2), how much ammonia (NH3) would you make?
5) If you used 140.0 g of Nitrogen (N2), how much hydroge (H2) would you need to react?