Molar Ratios

​Stoichiometry

Yeast bread rises because the yeast breaks down sucrose (C₁₂H₂₂O₁₁) during cellular respiration and reduces carbon dioxide. The zero Calorie sweetener Steviol (C₂₀H₃₀O₃) has a similar chemical structure. Is it possible to replace sugar with Steviol when baking? If so, is there anything else you need to do to the recipe?

Drag and Drop

Balance the Equation:​

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Zn + ​

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HCl→​

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H₂ + ​

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ZnCl₂

Drag these tiles and drop them in the correct blank above

1

2

3

4

5

6

7

8

Multiple Choice

Which type of reaction makes a new substance from one or more compounds?

• Combustion

• Single-Replacement

• Double-Replacement

• Decomposition

• Synthesis

Multiple Choice

Is Potassium carbonate soluble or insoluble?

• soluble

• insoluble

Drag and Drop

A(n)

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reaction absorbs energy from the surroundings, while an ​

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reaction releases energy into the surroundings.

Drag these tiles and drop them in the correct blank above

endothermic

exothermic

Combustion

Single-Replacement

Double-Replacement

Decomposition

Multiple Choice

What is the name for the solid formed during a reaction between aqueous substances?

• Precipitate
• Rocks
• Bubbles
• Aqueous solid

Multiple Choice

What does the reaction rate describe?

• How fast a reaction takes place

• What type of product a reaction creates

• Whether or not a reaction is reverseable

• How much heat a reaction will release

Lesson Objectives

• Analyze data and predict the stoichiometric ratios in a chemical equation

• Model the conservation of mass in a chemical equation

• Apply Math to interpret Chemical equations

Quantifying Reactants and Products

• Chemical equations work like a recipe

  • Balanced equations tell you the ingredients you need and the proper ratios

• Stoichiometry: The calculation of quantities in a chemical reaction​

  • Can be quantified in terms of moles, mass, volume, and number or atoms/molecules

    • The total amount of atoms remains the same throughout the equation due to the Law of Conservation of mass

Proportionality of Reactants & Products

• In a chemical equation, the chemical symbols tell you the ingredients, and the coefficients in front of them tell you the ratios in terms of moles

  • Example: N_2(g) + 3H_{2 (g)} → 2NH_{3 (g)}

    • For every 1 mole of N_2, you can get 2 moles of NH₃

    • For every 3 moles of H₂ you can get 2 moles of NH₃

    • You need at least 1 mole of N₂ and 3 moles of H₂ for the reaction to take place

Mole Ratios

• A mole Ratio is a conversion factor derived from the coefficients of balanced equations​

  • Can be used to determine the amount of reactant or product involved in a chemical reaction​

    • ​Example: N_2(g) + 3H_{2 (g)} → 2NH_{3 (g)}

Multiple Choice

For the Balanced Reaction:
3 Mg + 1 Fe₂O₃ → 3 MgO + 2 Fe;
What is the Ratio of moles of Mg to moles Fe?

• 3mol Mg / 2 mol Fe
• 2 mol Mg/ 3 mol Fe
• 1 mol Fe/ 2 mol Fe
• 3 mol MgO / 2 mol Fe

Multiple Choice

What is the mole ratio of Ba(OH)₂ to AlPO₄?

2AlPO₄ + 3Ba(OH)₂ → 2Al(OH)₃ + Ba₃(PO₄)₂

(Use the most simplified form)

• 3 mol Ba(OH)₂ / 2 mol AlPO₄

• 1 mol Ba(OH)₂/ 1 mol AlPO₄

• 2 mol Ba(OH)₂/ 3 mol AlPO₄

• 1 mol Ba(OH)₂/ 3 mol AlPO₄

Multiple Choice

What is the mole ratio of Mg to MgCl₂?

Mg + 2HCl → MgCl₂ + H₂

(Use the most simplified form)

• 2 mol Mg/ 1 mol MgCl₂

• 1 mol Mg/ 2 mol MgCl₂

• 1 mol Mg/ 1 mol MgCl₂

• 2 mol Mg/ 2 mol MgCl₂

Types of Stoichiometry Problems

• Several types of Stoichiometry problems

  • Mole-Mole

  • Mole-Mass (Mole-Volume, Mole-Molecules)

  • Mass-Mass​

Mole-Mole Calculations

• Mole ratios are used in mole-mole calculations

  • Converting between the moles of one reactant/product and the moles of another reactant/product​

    • Given: The Moles of one part of the balanced equation

    • Want: The Moles of another part of the balanced equation

Mole-Mole Calculations Sample Problem #1

• How many moles of O₂ would you need to produce 25 moles of H₂O ?from the following equation: 2H₂ + O₂ →​ 2 H₂O

  • Step 1: Identify what value you are starting with

    • 25 moles H₂O

  • Step 2: identify the molar ratio for what you need

    • Going from H₂O to O₂

Multiple Choice

How many moles of H₂O are in the following balanced equation: 2H₂ + O₂ →​ 2 H₂O ?

• 1

• 2

• 3

• 4

Multiple Choice

How many moles of O₂ are in the following balanced equation: 2H₂ + O₂ →​ 2 H₂O ?

• 1

• 2

• 3

• 4

Mole-Mole Calculations Sample Problem #1

• How many moles of O₂ would you need to produce 25 moles of H₂O from the following equation: 2H₂ + O₂ →​ 2 H₂O ?

  • Step 1: Identify what value you are starting with

    • 25 moles H₂O

  • Step 2: identify the molar ratio for what you need

    • Going from H₂O to O₂

  • Step 3: Set up your conversion

Mole-Mole Calculations Sample Problem #2

• How many moles of ammonium (NH₃) are produced when 0.60 moles of nitrogen react with hydrogen?

  • Step 1: Write a balanced equation

    • __N₂ + __H₂→​__NH₃

Dropdown

Balance the equation:

​

Select answer

N₂ + ​

Select answer

H₂ → ​

Select answer

NH₃

Mole-Mole Calculations Sample Problem #2

• How many moles of ammonium (NH₃) are produced when 0.60 moles of nitrogen react with hydrogen?

  • Step 1: Write a balanced equation

    • N₂ + 3H₂→​2NH₃

  • Step 2: Identify what you are starting with

    • 0.60 moles of Nitrogen

  • Step 3: Identify what ratio you need to get what you want​

Multiple Choice

Based on the equation

N₂ + 3H₂→​2NH₃

What is the molar ratio of N₂ to NH₃?

• $$\frac{1\ N_2}{3\ H_2}$$

• $$\frac{2\ NH_3}{1\ N_2}$$

• $$\frac{3\ H_2}{2\ NH_3}$$

Mole-Mole Calculations Sample Problem #2

• How many moles of ammonium (NH₃) are produced when 0.60 moles of nitrogen react with hydrogen?

  • Step 1: Write a balanced equation

    • N₂ + 3H₂→​2NH₃

  • Step 2: Identify what you are starting with

    • 0.60 moles of Nitrogen

  • Step 3: Identify what ratio you need to get what you want​

Mole-Mole Calculations Sample Problem #3

• Aluminum combines with oxygen gas to form Aluminum Oxide (Al₂O₃). How many moles of Aluminum are needed to form 3.7 mols of Aluminum Oxide?

  • Step 1: Write your balanced equation

    • ___Al + ___ O₂ →___Al₂O₃

Dropdown

​

Select answer

Al + ​

Select answer

O₂ → ​

Select answer

Al₂O₃

Mole-Mole Calculations Sample Problem #3

• Aluminum combines with oxygen gas to form Aluminum Oxide (Al₂O₃). How many moles of Aluminum are needed to create 3.7 moles of Aluminum Oxide?

  • 4 Al + 3 O₂ →2 Al₂O₃

  • Step 2: Identify the molar ratio you need

Multiple Choice

In the equation

4 Al + 3 O₂ →2 Al₂O₃

What is the molar ratio between Aluminum and Aluminum Oxide?

• $$\frac{4\ Al}{3\ O_2}$$

• $$\frac{3\ O_2}{2\ Al_2O_3}$$

• $$\frac{\text{ }4\ Al}{2\ Al_2O_3}$$

Mole-Mole Calculations Sample Problem #3

• Aluminum combines with oxygen gas to form Aluminum Oxide (Al₂O₃). How many moles of Aluminum are needed to create 3.7 moles of Aluminum Oxide?

  • 4 Al + 3 O₂ →2 Al₂O₃

  • Step 2: Identify the molar ratio you need

  • Step 3: Set up your Conversion Factor

Multiple Choice

2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O

Ethane (C₂H₆) combusts in the above reaction. What is the mole ratio of ethane to oxygen gas?

Multiple Choice

In the equation 2 Al₂O₃ → 4 Al + 3 O₂, what is the mole ratio of aluminum to oxygen?

• 10:6 
• 3:4
• 4:3
• 2:3