Stoichiometry Made Easy with Ketzbook

Key Concepts

Mole Concept

• A mole is a very large number of atoms (600 billion trillion or $6 \times 10^{23}$).
• Understanding the mole is crucial for stoichiometry as it refers to the number of things (atoms, molecules).

What is Stoichiometry?

• Derived from Greek: "stoichion" (element) and "metron" (measure).
• It's a method for measuring elements and chemicals in a reaction, analogous to a recipe in cooking.
• Balanced chemical equation = recipe.

One-Step Stoichiometry Problems

Example: Grilled Cheese Sandwiches

• Recipe: 2 slices of bread + 1 slice of cheese = 1 grilled cheese sandwich.
• Question: How to make 7 grilled cheese sandwiches?
• Calculation: $7 , sandwiches \times \frac{2 , slices , of , bread}{1 , sandwich} = 14 , slices , of , bread$.
• Principle: Unit conversion problem where the balanced equation is the conversion factor.

Chemistry Application

Haber Process (Formation of Ammonia)

• Reaction: $N_{2} + H_{2} \rightarrow NH_{3}$
• Balanced Equation: $N_{2} + 3H_{2} \rightarrow 2 NH_{3}$
• Ratios: $1N_{2} : 3H_{2} : 2NH_{3}$

Sample Problems

Problem 1: Moles of Nitrogen for Ammonia Production

• Question: How many moles of nitrogen needed to make 10 moles of ammonia?
• Calculation: $10 , moles , of , NH_{3} \times \frac{1 , N_{2}}{2 , NH_{3}} = 5 , moles , of , N_{2}$

Problem 2: Moles of Ammonia from Hydrogen

• Question: How many moles of ammonia can be made from 0.37 moles of hydrogen?
• Calculation: $0.37 , moles , of , H_{2} \times \frac{2 , NH_{3}}{3 , H_{2}} = 0.25 , moles , of , NH_{3}$

Important Notes

• Always use quantities in moles when doing stoichiometry.
• The balanced reaction serves as the conversion factor.

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