The main idea of the Reaction Particle Diagram was to learn the standard way of drawing particle diagrams. When given a reaction, you must...
1. Balance the equation
2. Draw the correct amount of molecules before the reaction (all spread out)
3. Draw the correct number of molecules after the reaction (including the excess molecules)
In class, we white-boarded the packet "Reaction Particle Diagrams" to go along with this idea. This helped us because it gave us a lot of examples and lots of practice to get us comfortable with drawing these diagrams.
Stoichiometry - limiting reactants
The main idea of limiting reactants in stoichiometry was to understand how to calculate mass of a reaction with limited amounts of reactants. To find the mass, set up two (or more) ratios of the given masses of the two (or more) elements to find which one produces the least amount of a substance. Then, once you find the least amount of product that can be made, go backwards to find the amount of other molecules used to make that product.
In class, we worked on a few worksheets (Stoichiometry(6), (7)). The worksheets allowed us to get some more practice with the new idea.
Stoichiometry - yield
The main idea of yield is that never in reaction is there going to 100% of all products as the result of a chemical reaction. There will be some left inside the container, making the amount of solution less than what is theoretically predicted.
We also got a worksheet in class (Stoichiometry 8 - Yield) to get use to doing these types of problems.
Empirical Formulas
Empirical Formulas describes the relative number of each type of atom in a compound. It is given as the smallest whole number ratios. For example, although glucose is C6H12O6, its Empirical Formula is CH2O. To find the empirical formula given the percent composition...
1. Assume there are 100g of the product in total. All percents given become grams.
2. Find how many moles of each molecule there are in the product.
3. Divide each number of moles by the smallest number of moles.
4. Make sure they are all whole number ratios.
We worked on a worksheet to become comfortable with the new material. There were lots of practice to do this.
In addition to this, we were introduced to Empirical Units and Molecular Formulas, and Mass Percent. Empirical Units and Molecular Formulas basically take the Empirical formula and multiplies it by the number of atoms in the compound, given the molecular molar mass of the compound.
Mass Percent is the percent of a specific element or molecule in a compound.
Main Ideas
All the ideas we learned this week connect because we need to know one concept in order to understand the next one. We are not able to find Empirical formulas without knowing the basics of Stoichiometry. This is the same for reaction particle diagrams, limiting reactants, yield, Empirical Units, molecular formulas, and mass percent. I understand the concepts of reaction particle diagrams, limiting reactants, yield, and empirical units/molecular formulas, but I think I need more practice on mass percent. I don't understand the question when it asks "Find the mass percent of the compound in the sample". If the compound is the sample, wouldn't it just be 100%? I understand the steps you take to find the answer, but I don't understand what the number in the answer represents. I feel that I participated well in the learning process because I helped out with white-boarding the answers to the worksheets. I'm fairly confident in the subject we learned this week. I just need to work on mass percent, and maybe a series of random practice problems to know when to use what method of ratios. Because these ideas are a lot like the concepts we learned last week, I have no change in my ideas. However, I'm wondering what kind of questions will be on the actual AP exam? Will these Stoichiometry problems be on there?
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