  # Tuesday Tutoring: Stoichiometry and Chemistry

Date
March 28, 2023
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In our previous posts, we discussed the importance of unit conversion and how to set up and solve stoichiometry problems using conversion factors. In this final post, we will wrap up our discussion on stoichiometry by exploring how to calculate the limiting reactant and percent yield.

The limiting reactant is the reactant that is completely consumed in a chemical reaction, limiting the amount of product that can be formed. To determine the limiting reactant, we first need to balance the chemical equation for the reaction and then compare the amount of each reactant present to the stoichiometric ratio in the balanced equation.

For example, let's say we have a chemical reaction involving 5 moles of A and 8 moles of B:

3 A + 2 B → C

To determine the limiting reactant, we need to calculate the amount of product that can be formed from each reactant. We can do this by using the stoichiometric ratio in the balanced equation:

• A: 3 moles A produces 1 mole C
• B: 2 moles B produces 1 mole C

Using this information, we can calculate the amount of product that can be formed from each reactant:

• A: 5 moles A x (1 mole C / 3 moles A) = 1.67 moles C
• B: 8 moles B x (1 mole C / 2 moles B) = 4 moles C

In this case, the limiting reactant is reactant A, as it produces the smaller amount of product.

The percent yield is a measure of how efficient a chemical reaction is at producing the desired product. It is calculated by comparing the actual amount of product produced to the theoretical amount of product that could be produced based on the balanced chemical equation.

For example, let's say we have a chemical reaction that produces 10 grams of product, based on the balanced equation:

A + B → C

If the stoichiometric ratio between A and B is 1:2, we can calculate the theoretical amount of product that could be produced from 10 grams of A:

• A: 1 mole A produces 1 mole C
• B: 2 moles B produce 1 mole C

Using this information, we can calculate the theoretical amount of product that could be produced from 10 grams of A:

• A: 10 grams A x (1 mole A / molar mass of A) x (1 mole C / 1 mole A) x (molar mass of C / 1 mole C) = X grams of C
• B: 20 grams B x (1 mole B / molar mass of B) x (1 mole C / 2 moles B) x (molar mass of C / 1 mole C) = Y grams of C

The theoretical yield is the sum of X and Y. The percent yield is then calculated by dividing the actual yield (10 grams) by the theoretical yield and multiplying by 100:

• Percent yield = (actual yield / theoretical yield) x 100

By calculating the limiting reactant and percent yield, we can better understand the efficiency and effectiveness of a chemical reaction, and adjust our processes accordingly.

The process of stoichiometry can also be seen as a metaphor for our spiritual growth and development. In the same way that stoichiometry involves identifying the starting and target points, calculating conversion factors, and solving for the unknown variable, our spiritual journey involves setting goals, identifying the steps needed to reach those goals, and taking action towards our spiritual growth. Just as stoichiometry can help us achieve greater efficiency and effectiveness in our scientific endeavors, a similar process of reflection, self-awareness, and intentional action can help us deepen our connection to the divine and grow spiritually. Through this process, we can gain a greater understanding of ourselves, our relationship to the divine, and our place in the world.