Stoichiometry Review

​Stoichiometry Review

​Please have a calculator and periodic table handy

​Georgia Standards of Excellence

SC3. Obtain, evaluate, and communicate information about how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.

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d. Use mathematics and computational thinking to identify and solve different types of reaction stoichiometry problems (i.e., mass to moles, mass to mass, moles to moles, and percent yield) using significant figures.

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e. Plan and carry out an investigation to demonstrate the conceptual principle of limiting reactants.​

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​1 mole= 6.02 x 10²³ particles

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1 mole= g molar mass (p-table)​

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1​ mole= 22.4L for a gas at STP

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​Mole Equalities

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A balanced equation tells you the mole ratio

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N₂ + 3H₂ ---> 2NH₃

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For every 1 mol for N₂ there are 3 moles of H₂ and 2 moles of NH₃​

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​Mole Ratio

Fill in the Blanks

N₂ + 3H₂  → 2NH₃ 

How many moles of hydrogen, H₂, are needed to react with 2.0 moles of nitrogen, N₂?

Fill in the Blanks

Zn + 2HCl → ZnCl₂ + H₂

How many moles of hydrogen are produced from the reaction of 3.0 moles of zinc?

Multiple Choice

49 grams of hydrogen sulfate are reacted with aluminum.  How many grams of aluminum are needed to do this? 

2Al + 3H₂SO₄  -->  3H₂ + Al₂(SO₄)₃

• 49 grams

• 0.33 grams

• 9 grams

• 27 grams

Multiple Choice

Ca(OH)₂  + 2HCl --> CaCl₂ + 2H₂O

Calcium hydroxide is reacted with hydrogen chloride to form 78 grams of water.  How much calcium chloride is made?

• 18 grams

• 78 grams

• 110 grams

• 238 grams

Fill in the Blanks

What volume of chlorine at STP is necessary for the complete reaction of 4.81 grams of sodium?

2Na(s) + Cl₂(g) --> 2NaCl(s)

​Limiting Reactants

Limiting Reactant: When 2 substances react, it is the one that is used up first.​

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Excess Reactant: When 2 substances react, it is the one that i​s not used up completely in a reaction.

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​Limiting Reactants

​Visual Clue that you have a limiting reactant problem

2 givens​

Multiple Choice

2H₂ + O₂ --> 2H₂O

12 grams of H₂ are reacted with 36 grams of O₂.

What is the limiting reactant?

• Hydrogen

• Oxygen

• Water

• There is not a limiting reactant

Multiple Choice

2H₂ + O₂ --> 2H₂O

12 grams of H₂ are reacted with 36 grams of O₂.

How much water is made?

• 12 grams

• 36 grams

• 41 grams

• 108 grams

Multiple Choice

2H₂ + O₂ --> 2H₂O

12 grams of H₂ are reacted with 36 grams of O₂.

What is the excess reactant?

• Hydrogen

• Oxygen

• Water

• There is no excess reactant

Multiple Choice

2H₂ + O₂ --> 2H₂O

12 grams of H₂ are reacted with 36 grams of O₂.

Calculate the amount of excess reactant.

• 4.5 grams

• 7.5 grams

• 12.5 grams

• 36.5 grams

​Theoretical, Actual, and Percent Yield

Theoretical yield: •The maximum amount of product calculated using the balanced equation.

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Actual yield: •The measured amount of product obtained when the reaction takes place.

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Percent yield: •The ratio of actual yield to theoretical yield.

 

Percent Yield = (Actual Yield/ Theoretical Yield) x 100​

Fill in the Blanks

Be + 2 HCl --> BeCl₂ + H₂

The theoretical yield of beryllium chloride was 10.7 grams. If the reaction actually yields 4.5 grams, what was the percent yield?

Fill in the Blanks

For the balanced equation shown below, if the reaction of 0.112 grams of H₂ produces 0.745 grams of H₂O, what is the percent yield?

Fe₃O₄ + 4H₂ --> 3Fe + 4H₂O

Open Ended

Do you have any questions or concerns about any of the types of Calculations that we reviewed today?