Lab 14: Titration Lab

Lab 14: Titration Lab

The purpose of this laboratory experiment was to determine the percentage of ionization of acetic acid. To determine the the percentage ionization we ascertained the amount of a constituent in the solution by measuring the volume of a known concentration of chemical required to complete a reaction. This process is called titration. We titrated the acetic acid with NaOH, a strong base. We poured 50 mL of NaOH into a burette and slowly dripped drops of it into an Erlenmeyer flask that contained acetic acid and an indicator called phenolphthalein so that we would know when the solution had reached equilibrium. All three of our trials resulted in our team missing the point of equilibrium between NaOH and acetic acid, but our last attempt gave us the most reliable molarity of the acetic acid. It was .83M and we had .85M. To calculate the percent ionization of the acetic acid we divided the H30+ concentration by the concentration of NaOH. To determine these concentrations we averaged the molarity of the acid for all three attempts and divided .004 by .81 to get a percent ionization of .49% This number is very low because acetic acid is a very weak acid and does not ionize well.  The hydrogen ions from the acid do not disassociate well because it is so weak, and this results in a low percent ionization.

The Setup

The final product (we missed the point of equilibrium but this was our most accurate attempt)

Lab 13B: Solubilty, A Guided Inquiry Lab

Lab 13B: Solubility, A Guided Inquiry Lab

Introduction: The purpose of this laboratory experiment was to test our knowledge of the process of solubility. We had to create our own procedure for determining the identity of the unknown solute that was to be dissolved in water. To do this we dissolved various amounts of the solute, the substance that was being dissolved, into the solvent, the substance that is dissolving the solute, in this case water. At different temperatures the solubility, or the amount a solute will dissolve in a solvent, changes. The higher the temperature, the higher the solubility and vice-versa. The purpose of the lab was basically to change the temperature and amount of solute to determine the identity of the solute. Other vocabulary terms were saturated- which is when a solution has dissolved the maximum amount of solute it can. Unsaturated- when a solution can still dissolve more solute.

Procedure: For this experiment we filled a beaker of water to 10 ml, and used a larger beaker to heat it up by putting the smaller beaker inside it. This removed temperature fluctuations. Then we dissolved approximately 4.30 grams of the substance at 36 degrees Celsius. It dissolved completely*, so we could rule of the NaCl substance because if it was NaCl it would have formed precipitate according to the solubility graph. The next part of the experiment was to increase the mass of solute to about 7.50 grams and keep the temperature at 40 degrees Celsius. When the water did not dissolve, we could confirm that the substance was not NaNO3, because it was under the solubility line and would have completely dissolved had it been NaNO3. To complete the final part of the experiment and confirm the identity of the substance, which at this point you can guess is KNO3, we increased the temperature to around 80 degrees Celsius and kept the mass at around 7.50 g. When we stirred the solution we noticed that the solid dissolved and this confirmed it at KNO3 because it was below the solubility line of KNO3. Some of the important materials we used were a graduated cylinder, a stirring rod, a scoopula, two beakers, a heating plate, a thermometer, a scale, a measuring plate, 10 ml water, and KNO3.

Data:

Mass of beaker- 29.74 g

Volume of water- 10 mL

Water temp- 21 C

Solute- KNO3

Conclusion: The unknown substance was KNO3. The reason we can be sure of the results was the evidence from the Solubility Chart. The first piece of evidence was that the solid did not dissolve at when we put conditions at 7 grams at 40 degrees. This did not dissolve and was under the solubility line for NaNO3 so we could rule out that substance. The next evidence was 4 grams of substance at 36 Celsius, and when it dissolved and was over the solubility line for NaCl we could rule it out as well. Therefore, the only substance it could possibly be was KNO3.

The illusive KNO3

Lab 12: Gases

Lab 12: Gases

For case 1, we studied the relationship between volume and pressure and found it to be inverse relationship. To do this , we set the temperature as the constant parameter and adjusted the volume of the box so that the pressure would change. 

For case 2, we studied the relationship between volume and temperature and determined that they were directly proportional. We picked a pressure and made that our constant. Then we adjusted volume and temperature and saw that they went up and down together.

For case 3, we studied the relationship between temperature and pressure and found them to be directly proportional. Volume was our constant in this one, and we adjusted the temperature to observe its relationship with pressure.

For case 4, we studied the relationship between the number of particles and volume and determined that they were directly proportional. We set pressure constant and set the number of particles to our choosing. The program changed the volume to accommodate the particles, and we saw that they increased and decreased together.

Spreadsheet of Data

In the spreadsheet we mistyped the first point for Volume versus Pressure. In the volume column, we have the first one as 1.78cm^3, but the point does not make sense. We could not find the actual point so we only have five points for this group.

4.
a. Bicycle tires seem more flat in the winter because of the relationship between volume and temperature. As the temperature goes down, the volume of the tire will go down too because the tire's particles slow and colliding with the boundaries of the tire less frequently.

b. A can of soda will explode if left out in the sun because of the relationship between temperature and pressure. As the temperature goes up, the pressure inside of the can will go up too due to the increasing speed of the gas particles inside. When the pressure gets so high that it can't be contained inside the can, it is released in an explosion.

c. The pressure will go down because as temperature goes down, pressure will also decreases. However, the volume should stay constant, because the container is rigid and will not expand or contract with the movement of the gas.

d. Using heat should will not help because of the relationship between heat and pressure. As heat increases, pressure will also increases. That heat would increase the pressure around the pain, and cause the person with the pain to regret his decision of not paying attention in chemistry class the day the relationships of pressure and temperature were explored.

Lab 11A: Specific Heat of a Metal

Lab 11A: Specific Heat of a Metal 

Today, the purpose of the experiment was to determine the identity of a metal by determining its specific heat and comparing it to known metals. This can be calculated by measuring the difference in temperature between a boiling metal block, and a room temperature one. Now we can use the amount of energy we can calculate the specific heat by using amount of joules.

Click here to view the data for the experiment.

Metal A, our metal block, is most likely brass because the specific heat of brass is 380, which is closest to the specific heat that we found, 329.

The benevolent metal Brass.

Lab 11B: Calories in Food Lab

Lab 11B: Calories in Food Lab

Question 1: We measured the change in temperature in the water above the calorimeter. We put the calorimeter over the food sample that was burning and then we put a flask of water on top of it. This way we could measure the temperature easily with the thermometer we were provided.

Question 2: We measured the energy gained by the water because the temperature of the water measures the energy gained by it.

Question 3: The small amount of energy that does not go into the water will go into the surroundings, or in this case the can and air around the experiment.

Question 4: I was surprised that the cheese puff burned very fast and then did not burn easily. I was also surprised that the pecan had the most calories of all the foods tested.

Lab 10: Evaporation and Intermolecular Attractions

Lab 10: Evaporation and Intermolecular Attractions

Data from the Lab and Pre-Lab

Questions:

1: In data table

2: The reason for the differences in the volatility between the different liquids can be founds in their bonds. Methanol, which was the most volatile, had the lowest number of hydrogen bonds, and was the smallest. Therefore it evaporated quickly. The next one was ethanol which was only slightly bigger than methanol so it evaporated more slowly. After that came water which has a double hydrogen bond, and after that came n-butanol. The reason that glycerin did not evaporate was that it was a fairly large molecule with many bonds, so it gathered heat instead of losing it to evaporation.

3: Water and methanol had similar molar masses, but their speeds of evaporation differ greatly. The reason for this is that water had two hydrogen bonds and methanol only has one. Waters intermolecular forces are higher than that of methanol.

4: The number of OH groups affects the evaporation rates of liquids because it is a hydrogen bond. The more OH groups a liquid has, the harder it will be for it to evaporate, because it requires more energy.

Lab 7: Flame Test

Lab 7: Flame Test

The main purpose of this experiment was to emphasize the concept that different chemicals or elements will emit different wavelengths when they are in excited states. These wavelengths on the visible spectrum are colors. The other purpose was to identify the two unknown substances based on the color they emitted when they were in an excited state. The setup of the lab was simple. We were provided a Bunsen burner to burn the compounds and sticks soaked with the different compounds. We held the stick above the lit Bunsen burner and watched as the compounds emitted different colors.

Lithium Chloride, one of the unknown substances, burning a magenta color

Pre-lab Questions:

Unknown Substances: #1. Lithium Chloride

                                     #2. Potassium Chloride

How we know: We can be sure that the two unknown substances are Lithium Chloride and Potassium Chloride because each each compound will emit a different wavelength when its electrons are in an excited state. The different emitted wavelengths correspond to a color that will be unique to that certain compound. For this reason, we can be sure that the compounds are correctly identified.