Chapter 4 SABIS Grade 10 Part 5

Lesson 20: Stoichiometric Calculations and Balancing Equations 🧮🔍🧪

Hello learners! 🔎💡 Today, we will explore how to balance chemical equations and conduct stoichiometric calculations. This exciting topic will deepen your understanding of chemical reactions and help you make accurate predictions. So let's get started! 🚀🧪

Prerequisite Material Quiz 📚🧠

1. What is a stoichiometric calculation?

2. Why do we need to balance chemical equations?

3. What does it mean if a chemical equation is balanced?

4. Is it possible to calculate the number of molecules or moles of a product from the number of molecules or moles of a reactant?

5. Can the number of moles of a reactant determine the number of moles of a product?

(Answers at the end of the lesson)

Explanation: Stoichiometric Calculations and Balancing Equations 🧐👩‍🔬

Stoichiometric calculations involve using the coefficients from balanced chemical equations to calculate quantities of reactants or products. These quantities can be in terms of moles, molecules, or mass.

Balancing chemical equations is a crucial step because it ensures the law of conservation of matter is obeyed. According to this law, matter cannot be created or destroyed. When a chemical equation is balanced, it means the number of atoms of each element is the same on both sides of the equation.

Examples 🌍🔬🔎

Let's look at the reaction N2H4 + O2 → H2O + N2.

1. Balancing the equation: To balance this equation, we can start by balancing the hydrogen atoms, and we'll find the balanced equation to be: N2H4 + O2 → 2 H2O + N2.

2. Number of molecules: One molecule of N2H4 gives 1 molecule of nitrogen gas and 2 molecules of water.

3. Number of moles: Similarly, one mole of N2H4 gives 1 mole of nitrogen gas and 2 moles of water.

Let's Practice More Examples! 👩‍🔬📚

1. Example 1: Consider the following reaction: CH4 + 2O2 → CO2 + 2H2O. If you have 1 molecule of methane (CH4), how many molecules of CO2 and H2O will you produce?

   • Answer: 1 molecule of methane will produce 1 molecule of CO2 and 2 molecules of H2O.

2. Example 2: Let's take another reaction: 2H2 + O2 → 2H2O. If we start with 1 mole of O2, how many moles of H2 and H2O will we have?

   • Answer: 1 mole of O2 reacts with 2 moles of H2 to produce 2 moles of H2O.

Post-lesson MCQs 📝✅

1. Why is it important to balance a chemical equation before performing stoichiometric calculations?

2. In a balanced equation, the number of atoms of each element on the reactants side is equal to what?

3. True or False: In a stoichiometric calculation, the number of moles of a reactant determines the number of moles of a product.

4. Is it possible to find the number of molecules of product formed from the number of molecules of a reactant?

5. What will one mole of CH4 produce in the reaction CH4 + 2O2 → CO2 + 2H2O?

(Answers at the end of the lesson)

Answers

Prerequisite Material Quiz:

1. A stoichiometric calculation involves using the coefficients from a balanced chemical equation to calculate quantities of reactants or products.

2. We need to balance chemical equations to ensure that the law of conservation of matter is obeyed.

3. A chemical equation is balanced when the number of atoms of each element is the same on both sides of the equation.

4. Yes, it is possible to calculate the number of molecules or moles of a product from the number of molecules or moles of a reactant.

5. Yes, the number of moles of a reactant can determine the number of moles of a product.

Post-lesson MCQs:

1. It is important to balance a chemical equation before performing stoichiometric calculations to ensure that the law of conservation of matter is obeyed.

2. In a balanced equation, the number of atoms of each element on the reactants side is equal to the number of atoms of the same element on the products side.

3. True

4. Yes, it is possible to find the number of molecules of product formed from the number of molecules of a reactant.

5. One mole of CH4 will produce 1 mole of CO2 and 2 moles of H2O.