Housekeeping: Are we making progress on our IA topics? Send me an email that contains your RQ, hypothesis and variables. Tell me what kind of quantitative data you're going to collect and how much time you will need. [email protected]. I want these emails before the end of the day.
We are working in Chapter 1, Section 2 of your textbook. HL students get a break, as this chapter does not have a HL section. There are quite a few activities, and two of them you will write up as labs.
Agenda:
1. Housekeeping
2. Experimentation with SR and DR reactions
3. Analysis of results
4. Percent composition
5. Empirical & molecular formulas
Content Review:
Links: Empirical & Molecular Formulas Percent Composition
Textbook Readings: Section 1.2
Student Missions:
Mission 1: Real Chemistry
Mission Objectives. You should be able to...
1. Observe and describe the reactants and products of a chemical reaction.
2. Determine the percent yield of the reaction.
3. Explain whether or not mass was conserved.
As we've been talking about, chemical reactions summarize chemical change and are represented by chemical equations. Reactants are on the left and products are on the right. Equations are balanced using coefficients to ensure that mass is conserved (we can't break that law, y'all). State symbols are used to denote the state of matter each reactant and product are in at the time of reaction.
Reminder: (s) = solid (l) = liquid (g) = gaseous (aq) = aqueous (dissolved in water)
Having said all that, let's take a look at some chemical reactions. You need to predict the results, measure the amount of reactants that you used and determine how much product you should have obtained.
You will complete the following reactions: zinc in hydrochloric acid, magnesium in hydrochloric acid, and aqueous sodium hydroxide in hydrochloric acid. For each reaction, you should measure out 5.0 grams of each solid and 10.0mL of each solution. Be very careful when measuring. From this, determine the amount of moles of each reactant you use. You will determine the theoretical amount of products and compare what you actually obtained to what you should have obtained. This is percent yield. Below is a video showing you how to calculate percent yield.
We are working in Chapter 1, Section 2 of your textbook. HL students get a break, as this chapter does not have a HL section. There are quite a few activities, and two of them you will write up as labs.
Agenda:
1. Housekeeping
2. Experimentation with SR and DR reactions
3. Analysis of results
4. Percent composition
5. Empirical & molecular formulas
Content Review:
Links: Empirical & Molecular Formulas Percent Composition
Textbook Readings: Section 1.2
Student Missions:
Mission 1: Real Chemistry
Mission Objectives. You should be able to...
1. Observe and describe the reactants and products of a chemical reaction.
2. Determine the percent yield of the reaction.
3. Explain whether or not mass was conserved.
As we've been talking about, chemical reactions summarize chemical change and are represented by chemical equations. Reactants are on the left and products are on the right. Equations are balanced using coefficients to ensure that mass is conserved (we can't break that law, y'all). State symbols are used to denote the state of matter each reactant and product are in at the time of reaction.
Reminder: (s) = solid (l) = liquid (g) = gaseous (aq) = aqueous (dissolved in water)
Having said all that, let's take a look at some chemical reactions. You need to predict the results, measure the amount of reactants that you used and determine how much product you should have obtained.
You will complete the following reactions: zinc in hydrochloric acid, magnesium in hydrochloric acid, and aqueous sodium hydroxide in hydrochloric acid. For each reaction, you should measure out 5.0 grams of each solid and 10.0mL of each solution. Be very careful when measuring. From this, determine the amount of moles of each reactant you use. You will determine the theoretical amount of products and compare what you actually obtained to what you should have obtained. This is percent yield. Below is a video showing you how to calculate percent yield.
You need more practice with calculations, so here ya go.
Mission 2: Part vs. Whole
Mission Objectives. You should be able to...
1. Explain what percent composition means in terms of a compound.
2. Calculate percent composition.
Mission 2: Part vs. Whole
Mission Objectives. You should be able to...
1. Explain what percent composition means in terms of a compound.
2. Calculate percent composition.
Let's Practice!!!
Mission 3: Empirical vs Molecular Formulas
Mission Objectives. You should be able to...
1. Distinguish between empirical formulas and molecular formulas.
2. Determine the empirical formula of a compound.
3. Determine the molecular formula of a compound.
Mission 3: Empirical vs Molecular Formulas
Mission Objectives. You should be able to...
1. Distinguish between empirical formulas and molecular formulas.
2. Determine the empirical formula of a compound.
3. Determine the molecular formula of a compound.
Let's Practice!!!
Homework: Complete the practice problems for each mission. I will email you more practice problems.
Limiting Reactants. Chemical reactions should theoretically go to completion, but they do not because some reactants are used up faster than others. The reactant that runs out first (the limiting reactant or limiting reagent) determines the amount of product that is formed. For example, if you're making cheese sandwiches and you have 16 pieces of bread and five pieces of cheese, but the recipe calls for two pieces of bread and one piece of cheese...how many sandwiches can you make before you run out of ingredients? Which is the limiting ingredient? Which is the excess ingredient (the reactant that is left over)?
In order to complete LR/ER problems, you need to remember how to read a balanced chemical equation and determine the correct mole ratios. Basically, the mole ratio is key in determining how much product is obtained.
Having said that, here's a quick-N-easy set of guidelines on solving LR problems.
Here's an IB-level video to give you an idea of the math that is involved in understanding the concept. Don't go crazy over doing the problems; we will work those out in class. Just try to understand the concept and get familiar with how to do the work.
Homework: Complete the practice problems for each mission. I will email you more practice problems.
Limiting Reactants. Chemical reactions should theoretically go to completion, but they do not because some reactants are used up faster than others. The reactant that runs out first (the limiting reactant or limiting reagent) determines the amount of product that is formed. For example, if you're making cheese sandwiches and you have 16 pieces of bread and five pieces of cheese, but the recipe calls for two pieces of bread and one piece of cheese...how many sandwiches can you make before you run out of ingredients? Which is the limiting ingredient? Which is the excess ingredient (the reactant that is left over)?
In order to complete LR/ER problems, you need to remember how to read a balanced chemical equation and determine the correct mole ratios. Basically, the mole ratio is key in determining how much product is obtained.
Having said that, here's a quick-N-easy set of guidelines on solving LR problems.
Here's an IB-level video to give you an idea of the math that is involved in understanding the concept. Don't go crazy over doing the problems; we will work those out in class. Just try to understand the concept and get familiar with how to do the work.
Let's practice!!!
Today in class, we will run some LR/ER demos using aluminum foil and copper (II) chloride. You will measure out 1.0g of aluminum foil and combine that with 10mL of aqueous copper (II) chloride. Once you put the foil in the solution, allow the reaction to go for 10 minutes or until the bubbles stop forming, whichever comes first. While waiting, do the following:
1. Predict the products and write the balanced chemical equation.
2. Convert the amounts into moles using the molar mass.
3. Determine the theoretical yield of each product.
After 10 minutes, carefully remove the aluminum from the solution. Gently scrape the brown solid onto a piece of filter paper and put it to the side to dry. If there is brown solid remaining in the test tube, remove it using forceps and put it on the filter paper.
THEN...
1. Take the mass of the remaining aluminum foil.
2. Take the mass of the brown solid.
3. Pour the remaining blue copper solution into a graduated cylinder and record the volume.
4. Determine the percent yield of each product. At what point did you lose products?
5. Determine whether mass was conserved. What were the bubbles that formed in the copper solution as the reaction took place?
After that, you must determine which reactant was the LR and which was the ER. You should also determine how much of the excess reactant was used and how much was left over.
Today in class, we will run some LR/ER demos using aluminum foil and copper (II) chloride. You will measure out 1.0g of aluminum foil and combine that with 10mL of aqueous copper (II) chloride. Once you put the foil in the solution, allow the reaction to go for 10 minutes or until the bubbles stop forming, whichever comes first. While waiting, do the following:
1. Predict the products and write the balanced chemical equation.
2. Convert the amounts into moles using the molar mass.
3. Determine the theoretical yield of each product.
After 10 minutes, carefully remove the aluminum from the solution. Gently scrape the brown solid onto a piece of filter paper and put it to the side to dry. If there is brown solid remaining in the test tube, remove it using forceps and put it on the filter paper.
THEN...
1. Take the mass of the remaining aluminum foil.
2. Take the mass of the brown solid.
3. Pour the remaining blue copper solution into a graduated cylinder and record the volume.
4. Determine the percent yield of each product. At what point did you lose products?
5. Determine whether mass was conserved. What were the bubbles that formed in the copper solution as the reaction took place?
After that, you must determine which reactant was the LR and which was the ER. You should also determine how much of the excess reactant was used and how much was left over.
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