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*Lesson 7.9: How can we predict the quantity of products in a chemical reaction?  

Review:

  1. When we made the compound found in oyster shells in Unit 5, we used the following reaction.

CaCl2 (aq) + Na2CO3 (aq) → CaCO3(s) + 2 NaCl (aq)

How much CaCl2 and Na2CO3 is needed to make an average sized oyster shell with a mass of 85.1g of CaCO3? (molar mass of CaCl2  = 110.98g/mol, molar mass of Na2CO3 = 105.99g/mol)

  1. What did we learn last class about calculating the moles or mass of a chemical reaction?

the moles in a reaction are proportional to the coefficients in a balanced equation

  1. Complete the IMT for Lesson 8.

Reactants, Products, and Leftovers Simulation  Click on the link, click on sandwiches, click on meat and cheese option. Use the simulation and filli in the chart below using the equation: 2Bd + Ch + Me → Bd2ChMe

Slices of Bread Pieces of Meat Pieces of Cheese Sandwiches made Leftover ingredient Limiting ingredient
2 1 2 1 cheese bread
4 1 3 1 cheese, bread meat
8 5 2 2 meat, bread cheese
10 5 5 5 none none

Part 1: Follow Up Lab: An interaction of two substances

PRE-LAB Questions: 

After reading the lab procedures, answer the following questions. When you finish, show your instructor. 

  1. When we did this lab previously, we used 3 flasks with balloons. The mass of baking soda was 1.5g, 3.0g and 6.0g while the volume of vinegar stayed the same, 50mL. Draw a sketch of the 3 balloons.

  2. What did you learn from our previous investigation? 

An Interaction of 2 substances… Part 2

Materials:

A clean 125 or 250 mL erlenmeyer flask NaHCO3  (Sodium Bicarbonate) 

1 balloons HC2H3O2 (Acetic Acid)  

Graduated cylinder balance and weigh boat

Procedure:

A. Preparing the flasks:

  1. Using the graduated cylinder, measure out 50 mL of acetic acid, pour into an Erlenmeyer flask

  2. Measure out, using the weigh boat, 3.00g of sodium bicarbonate. 

  3. Flex the weigh boat, have a partner pull open the neck of the balloon, and pour the 3.00g of sodium bicarbonate into the bottom of the balloon.  

  4. Keeping the sodium bicarbonate at the bottom of the balloon, stretch open the neck of the balloon and attach it securely down the threads at the top of flask #1.  See image.

  5. Let the balloon hang down.

B. Creating the phenomenon:

  1. Tip up the balloon so that ALL the sodium bicarbonate goes down into the acetic acid.

  2. Swirl your flask well until the reaction stops.

  3. Find the volume of the balloon. There are 2 ways to do this, if you need help deciding ask your instructor. 

  4. Remove the balloon and pour the left over contents down the drain.

Part 2: Calculations and Analysis

Analysis Questions

  1. What volume of carbon dioxide gas was produced from this reaction? 
C = 36.5 cm

V = (4/3)*pi*(C/(2pi))^3

L = V/1000
  1. How many moles carbon dioxide gas were produced? Use PV = nRT to calculate. (Temp of the room, and pressure=1 atm)
P = 1
V = 0.821
R = 0.0821
T = 298

n = (P*V)/(R*T)
  1. How many moles of HC2H3O2 (Acetic Acid - molarity 0.8527M) reacted (50mL)?
V = 0.050
M = 0.8527
mol_vinegar = V * M
  1. How many moles of NaHCO3  (Sodium Bicarbonate) were used? (molar mass = 84.01g/mol)
V = 0.050
M = 0.8527
mol_vinegar = V * M
  1. What mass of CO2 should be produced based on the mass of Acetic Acid? Use stoichiometry to calculate a theoretical yield. 
vol_vinegar = 0.05 ml
molarity_vinegar = 0.8527 mol/L
mol_vinegar = vol_vinegar * molarity_vinegar
molar_mass_vinegar = 60.052 g/mol
mass_vinegar = mol_vinegar * molar_mass_vinegar

mol_CO2 = 0.033557 mol
molar_mass_CO2 = 44.01 g/mol
mass_CO2 = mol_CO2 * molar_mass_CO2

  1. What mass of CO2 should be produced based on the mass of Baking Soda ? Use stoichiometry to calculate a theoretical yield. 

  2. Calculate percent error.  % yield = theoretical - actual / theoretical x 100

  3. How does the moles of carbon dioxide produced in your experiment compare with the calculated value? 

Part 3: Finding the Limiting Reactant

STEPS:  One way to find the limiting reactant is by calculating and comparing the amount of product each reactant will produce.

  1. Balance the chemical equation for the chemical reaction.

  2. Convert the given information into moles.

  3. Use stoichiometry for each individual reactant to find the mass of product produced.

  4. The reactant that produces a lesser amount of product is the limiting reactant.

Example: 

Calculate the mass of magnesium oxide possible if 2.40 g Mg reacts with 10.0 g of O2

Mg + O2 → MgO

Step 1 Balance the equation:      2Mg + O2 → 2MgO

Step 2 & 3  Convert mass to moles and use stoichiometry to determine the amount of product formed. 

2.40g Mg 1 mol Mg 2 mol MgO 40.31MgO = 3.98g MgO
24.31g Mg 2 mol Mg 1 mol MgO
10.0g O2 1 mol O2 2 mol MgO 40.31MgO = 25.2g MgO
32.0gO2 1 mol O2 1 mol MgO

Step 4 Compare the amount of product formed to determine the limiting reactant. 

Mg produces less MgO than O2 does therefore Mg is the limiting reactant

  1. 12.3g C3H8 reacts with 4.02g O2. What is the limiting reactant for this reaction? 

Step 1: ____ C3H8  + ____O2 → ____CO2 + ____H2O 

Step ⅔: 

=
=

Step 4: 

  1. Sodium hydroxide reacts with carbon dioxide as follows: What is the limiting reactant when 73.9g NaOH and 44.01g CO2 react? 

____ NaOH(s) + ____ CO2(g) → ____ Na2CO3(s) + ____H2O(l)

  1. 2.00L of O2  gas at standard temperature and pressure (0.0oC and 1.00 atm) reacts with 2.20g of liquid butane. What is the limiting reactant? (Use PV=nRT to find moles of O2)

____ C4H10  + ____O2 → ____CO2 + ____H2O 

NEXT STEPS:

  1. Reflect on today’s question: Limiting Reactant? 

  2. Reflect on the unit question, how does today’s activity relate to the unit question? 

  3. Make sure all parts of the L7.9 student sheet are complete.**

Last update: June 5, 2023
Created: June 5, 2023