Lab 14: Titration Lab


In this lab, we wanted to find the percent ionization of acetic acid in vinegar. To do this, we titrated a weak acid (acetic acid) with a strong base (sodium hydroxide). We began by filling up a burette to the zero point with 0.25 M NaOH and then we used a graduated cylinder to measure out 7.6mL of vinegar (CH3COOH) into a flask. Next, we added 20 mL of distilled water and a few drops of phenolphthalein (acid-base indicator) to the flask. We used a hot plate and magnetic stirring bar to stir our solution as we added  drops of NaOH to the base-filled flask. We began by slowly adding in drops of acid, but as the pink color remained longer, we dropped the rate of drops even lower. Finally, we added NaOH drop by drop until we reached a very light pink solution.

The setup

Our analyte at the equivalence point

 

Our final percent ionization of vinegar was 0.46%. This percentage is a low number because acetic acid is a weak acid, therefore the reaction between the acid and the base doesn't result in 100% complete ionization and not many hydronium atoms are present in the solution.



Lab 13: Solubility: A Guided Inquiry Lab

Introduction:
In this lab, we identified an unknown salt using the solubility curves of known solids (NaNO3, KNO3, and NaCl). Solubility can be defined as the ability for a substance to dissolve and solubility often increases as temperature increases (which creates the solubility curve). In a solution, there is always a solvent and solute. A solvent can be defined as a substance that dissolves another while a solute is defined as the minor component dissolved in a solution. My lab partners and I created a procedure involving the heating of water to dissolve certain amounts of the mystery substance. By finding the solubility of the substance, we were able to use the given solubility curves to identify the substance.

Procedure:

1. First, we measured out 10 mL of distilled water in a small graduated cylinder and poured it into a small beaker.
2. We began heating our hot water bath (the distilled water beaker in a larger beaker filled with regular water) to our chosen temperature of 45°C using a thermometer and a hot plate. We chose 45°C because that temperature had a large variation in solubility between the three solubility curves, therefore it would be more easy to distinguish between the different substances after finding the solubility of the mystery salt.
3. While the hot bath heated up, we measured out 4.8 g of the mystery salt using a scale. We wanted to use 4.8g of solute at first because it clearly lies over the NaCl curve, but under the KNO3 curve.
4. We poured the 4.8g of solute into the small beaker with distilled water and mixed the solution with a stirring rod. After a few minutes we found the solution remained unsaturated since all the solute dissolved in the solvent. This means the substance is not NaCl.
5. We continued to mass and add 3.5 g more of solute because a total of 8.3g of solute lies over the KNO3 curve while definitely lying under the NaNO3 curve. After a few minutes, all the added solute dissolved in the solution and the solution still remained unsaturated. This means the substance is also not KNO3.
6. By now, we knew the substance must've been NaNO3, but we continued our third test for confirmation. We massed and added 3.4g to our previous solution and later found our solution was finally saturated. This meant our substance was for sure NaNO3.

Data:
Trial 1 (NaCl testing)- Dissolved solute (unsaturated solution)
Mass of solute: 4.8g
Mass of solvent: 10g
Temp: 45°C

Trial 2 (KNO3 testing)- Dissolved solute (unsaturated solution)
Mass of solute: 8.3g
Mass of solvent: 10g
Temp: 45°C

Trial 3 (NaNO3 testing)- Undissolved solute (saturated solution)
Mass of solute: 11.7g
Mass of solvent: 10g
Temp: 45°C

Concluding Summary:
The mystery solute we had was NaNO3. Our claim was justified when we found that 4.8g of solute (above the NaCl solubility curve) and 8.3g of solute (above the KNO3 solubility curve) both fully dissolved and produced unsaturated solutions. Our third test for NaNO3 produced a saturated solution, meaning NaNO3 was certainly our substance. The relationship between the solubility and temperature is that as the temperature of a substance increases, the solubility of the substance also increases. This relationship in the solubility curves is what overall helped us identify the mystery salt.

Lab 12: Alka Seltzer and the Ideal Gas Law

 In this lab, solid sodium bicarbonate (NaHCO3) and citric acid (C6H8O7) reacted with water (H2O) to produce CO2. We collected the CO2 that was given off and used it in the ideal gas law to determine the amount of gas produced. By using a balloon filled with Alka Seltzer powder and a test tube full of water, the powder reacted with the water to produce CO2 that inflated the balloon. Once the reaction ended, we measured the circumference of the inflated balloon and filled the balloon up with water until the water balloon had the same circumference as the gas balloon. We used the water volume in the ideal gas law to finally calculate the amount of CO2 in the balloon.

My Data Table

My Calculations

CO2 inflating the balloon

Analysis Questions:
1. There are multiple areas experimental error may have occurred. For example, we could have inaccurately measured the circumference of the CO2-filled balloon or we could have dropped some powder while transitioning it from the mortar to the balloon. I also know that some water escaped the balloon as we were trying take it off the sink head and pour it into the graduated cylinder.

2. If water leaked out from the balloon, the recorded volume of the balloon would be smaller than the actual volume of the balloon. Since volume has a direct relationship with mass according to Avogadro's law, the number of moles ("n") of CO2 would be too small.

3.  38.00cm= 2πr --> r=6.05cm; V=4/3π (6.05cm)^3= 926.6cm^3= 926.6mL

4. The two volumes (experimental and calculated) of the balloon appear close. I feel that the experimental volume of the balloon is more accurate than the calculated volume because the shape of the balloon is not a perfect sphere. Although some human error may have effected the final numbers of the experimental volume, it is still more accurate than the calculated volume of the balloon.

5. Real gas molecules have interactive forces such as repulsion and attraction while ideal gases aren't supposed to have any interactive forces according to the kinetic molecular theory of gases. This theory also states how ideal gases should not lose energy from collisions with objects or other gas particles, but real gases do not have elastic collisions and tend to lose energy in any collision.

6. The CO2 in this lab would not be considered an ideal gas because ideal gases don't exist and it takes up mass and volume.

Advanced Questions:
1. Each tablet had 1000 mg of citric acid (C6H8O7) and 1916 mg of baking soda (NaHCO3). Using three Alka Seltzer tablets, we found that 3g of citric acid produced 2.062 g of CO2 while 5.74g of baking soda produced 3.011 g of CO2. Since citric acid was the limiting reactant, the theoretical yield is 2.062 g CO2.

2. 1.86g CO2/ 2.062g CO2= 90.2%

3. Some of the CO2 may have been dissolved in the water and therefore was not measured in the balloon as part of the gas volume. This explains how out calculated amount of CO2 appeared higher than our actual amount of CO2 obtained.

Lab 11B: Calories in Food Lab



In this lab we found the number of Calories per gram of different food items using a calorimeter. Each piece of food (a cashew, pecan or cheese puff) was lit on fire and covered with a tin can. The tin can "stove" heated up a flask of water and a change in water temperature was recorded using a thermometer. By using the mass of the food burned, the change in water temperature, and the specific heat of water, we were able to calculate the Calories per gram of each food type.

 

 

Questions #1-#4
1. Since it isn't possible to directly measure the temperature change of a food item, we measured the temperature change of the water. The amount of heat absorbed by the water in the flask is equivalent to the amount of heat given off by the burning food, therefore we know the temperature change of the water would be equivalent to the temperature change of the burning food sample.

2. The energy released by the food sample was gained by the water, therefore we measured the same amount of energy for both the food and the water.

3. The small amount of energy that was not absorbed by the water escaped into its surroundings. The glass flask or tin can may have absorbed some energy, while some energy may have also escaped through the holes of the tin can into the air.

4. I was surprised that the nuts contained more Calories than the cheese puffs because I have always been told that "unhealthy foods" contain more Calories than "healthy foods", but this lab challenged my knowledge of Calories in comparison to healthiness. I also was surprised that cheese puffs had a higher Calories/gram compared to the nuts because I didn't process how the mass of large cheese puffs are still light compared to a small nuts.

Lab 10: Evaporation and Intermolecular Attractions

Pre-Lab Table

My Data Table

Questions #2-#4
2. There was a wide range of temperature differences as shown in my data table above. Even though all of the substances had the same intermolecular attractive force, some substances had stronger forces than others. A substance with weaker hydrogen bonds (even though it is not an actual bond) will evaporate faster, which leads to a larger temperature difference and higher vapor pressure. Evaporation is a process that involves the use of energy which is why the temperature of the substance often decreases as it loses energy. The more a substance evaporates, the more energy it used and the lower the minimum temperature will be.

3. In this particular lab, Ethanol (molar mass= 46.068) and Methanol (molar mass= 32.0416) were the two compounds with similar molar masses. After experimentation, we found Methanol had the quicker evaporation rate and the larger temperature difference. This result was expected because Ethanol does have a slightly larger molar mass than Methanol. A larger molar mass indicates a substance contains more electrons and a greater number of electrons increases the strength of a substances intermolecular forces. A compound with stronger forces needs more energy to evaporate and therefore it is took less energy for Methanol to evaporate compared to Ethanol.

4. Hydrogen bonds are the strongest type of covalent bonds. The more hydrogen bonds a substance contains, the more energy it needs to break and change in the form of evaporation. In this lab, Glycerin contained the most amount of OH- groups and therefore it needed the most energy to evaporate. Our data shows how Glycerin actually increased in temperature because it was absorbing heat from the room rather than evaporating.  

Lab 7: Flame Test Lab

In this lab, we wanted to determine two compounds using flame tests to compare the flame colors various compounds produced. We held wooden sticks over the flame of the Bunsen burner and the  compound on the stick changed the color of the flame. We used the flames colors of known compounds to identify the unknown compounds. 
 
Pre-Lab Questions:
1. Ground state is the most stable energy state where all the electrons are in the lowest energy levels available. This normal electron configuration differs from excited state, which involves the "jumping" of electrons to higher energy levels due to the absorption of energy from heat at high temperatures. The excited configuration is very unstable and electrons will eventually "drop" to positions of lower energy.

2. Emit means to produce or discharge. For example, the sun emits radiation which means it produces and releases radiation.

3. Atoms are getting their excess energy from the heat of the flame. The flame from the Bunsen burner is exciting the electrons of the substance.

4. Atoms of different substances release different amounts of energy while the electrons are falling back down to ground state. A specific number of electrons in an atom release a certain amount of energy which changes the color of the light produced by a compound.

5. You need to clean the wire to make sure no residue is left from the previous substance. If the cation of the last compound still remained on the wire, it could change the color produced by a mixture of compounds. The wire would not create clear and accurate data.

A picture of Unknown #1 in the flame

Unknown #1: LiCl
Unknown #2: KCl
We were able to identify the unknowns by comparing the color of the flame created by the unknowns to the color of the flames we recorded from our 8 known compounds. We found that unknown #1 created a magenta color flame, just like LiCl did and unknown #2 created a light purple flame, just like KCl did.

Lab 8: Electron Configuration Battleship

The biggest challenge I had was naming elements in the f- block. I continually chose the wrong noble gas when trying to name the correct row in the f block. For example, I would accidently use Radon to name the 4Fs, but Radon is actually the noble gas before the 5Fs. During this challenge, I learned how to properly name the noble gas configurations of elements in the Lanthanides and Actinides.

Lab 6: Mole-Mass Relationships Lab

The purpose of this lab was to practice calculating theoretical yield and percent yield using our experimental data. We also had to find the limiting reactant of NaHCO3(s) + HCl(aq) => NaCl (aq) + CO2(g) + H2O(g) by looking at the relationship between the reactants and how much product they each produced. Overall, we found that NaHCO3 was our limiting reactant and we were able to successfully have a 100% yield.

Questions #1-#4

 

 

Even though our percent yield was 100%, I believe we did lose some mass when our remaining solid product popped once on the hot plate, but the small amount of water still left in the evaporating dish made up for that lost mass. The fluctuating of the scale is also another reason that error may occur and it could've possibly affected our percent yield if we did not read the scale as accurately as we did.

 

 



My lab partner and I also found it interesting that when we touched the tongs to the remaining solid in the evaporating dish, the solid turned into a yellow-green color due to contamination. 

 

Lab 5B:Composition of a Copper Sulfate Hydrate Lab

Before heating

After heating

Calculations for Questions #1-#4

Possible explanations for percent error include the false reading of the scale while it was fluctuating or not waiting long enough for all the H2O to evaporate.

Question #5
Moles of water evaporated- 0.014 mol H2O
Moles of CuSO4- 0.0032 mol CuSO4
Ratio of moles of CuSO4 to H2O- 1:4
Empirical formula- 1CuSO4 is loosely bonded to (dot symbol) 4H2O
We predict our predicted coefficients are slightly low compared to the actual value, even though our percent error isn't high.  To have a percentage of water closer to 36%, more water needed to be lost and therefore the ratio of Copper Sulfate to water would increase. 

Lab 5AL Mole Baggie Lab

In this lab, we needed to determine mystery substances in plastic bags using given measurements of the substance. We began by weighing the filled bag on the scale to find the total mass, and then we also used our given total mass to find the mass of our substance. For Set A, we calculated the molar mass by dividing the mass of the substance by the given number of moles. For Set B, we first converted the given number of respective particles to moles, and then we calculated the molar mass using the same given formula. Next we compared our calculated molar masses to the molar masses of the possible compounds. Our results were A4 is Calcium Carbonate and B3 is Potassium Sulfate.

Lab 4A: Double Replacement Reaction Lab

Complete molecular and net ionic equations #1-#5



Complete molecular and net ionic equations #6-#10

 



My well plate

 In this lab, I was surprised on how easy it was to write net ionic equations. After I completed writing the molecular equation for each reaction, I used any solid products to write a separate net ionic equation beneath. The shortcut of breaking down the solid compound to its separate polyatomic ions and elements made it very easy to write the net ionic equation. The most challenging part of this lab was finding out the solubility of each compound in the complete molecular equations. I needed to continually look at the solubility rules to find out what compounds were insoluble or soluble. The many exceptions in the solubility rules made this even more challenging.

Lab 3: Nomenclature puzzle

The goal of this lab was to complete a puzzle by matching binary and polyatomic ion formulas to their name. This puzzle was good practice on using the naming rules we learned in class today. The biggest challenge during this activity was searching for certain names that were already part of small groups. At the beginning, it was more simple to match names and formulas because we divided by the triangle pieces by the elements on the triangle, but it became more difficult as more and more small groups formed. I believe my biggest contribution to the group was putting the small groups of triangles together, making it easier to find certain triangles. I also helped assign certain elements to certain people, making the process flow more quickly.

Our completed puzzle

Lab 2B: Atomic Mass of Candium

In this lab we used three different isotopes of candium: regular M&M's, peanut M&M's and pretzel M&M's. The purpose of this lab was to practice calculating average atomic mass and to understand isotopes. We also were able to apply our new terms such as atomic number, atomic mass and natural abundance. Our calculated average atomic mass of candium was 1.357g. 

Conclusion:
     1. We compared with another group and found their average atomic mass to be 1.689g. It is possible they have a different answer than us because of human error such as counting incorrectly or not properly weighing the M&M's. It is also possible that each group started with a different amount of each type of M&M, therefore having a differing average atomic mass.

     2. If everyone were given a larger sample of candium, the difference between our average atomic mass and everyone else's atomic mass would become smaller because the larger sample size would create a more similar ratio of each type of M&M's and therefore the result would be more precise.

     3. If we took any piece of candium from the sample and put it on the balance, it wouldn't have the exact same atomic mass that I calculated because each type of M&M has its own distinct weight and none of the M&M's alone could weigh the average mass.

     4.

Lab 2A: Chromatography

 

My favorite chromatogram

Lab Questions:

     1. The wick was used to slowly add water to the center of the filter paper and this lab only works when you can visually see the separation of pigment. If we soaked the filter paper itself in the cup of water, the separation of colors on the paper would be too quick and wouldn't be clear which defies the purpose of this experiment.

     2. Different types of ink with various amounts of pigments affects what colors appear on the paper. I also found that more ink on the paper changed the color to a more darker tone. The distance the ink is from the wick and the design drawn also affect the pattern of colors produced.

     3. Different components of the ink have various physical properties and these properties determine how adsorbent certain pigments are to the filter paper. Components in the mixture that are more adsorbed to the paper will move more slowly compared to components in the mixture that aren't as adsorbed to the paper. These not so strongly adsorbed components spend more time ion the solution and move up the paper quickly. The various properties and adsorbing of pigments results in different pigment bands.

     4. Blue appears in more than one type of ink and the same shade of blue always appears. This light blue color was found on the edges of multiple chromatograms which means the blue pigment was not strongly adsorbed by the filter paper. All the markers appeared to have this common blue pigment.

     5. Water is needed to separate pigments in water-soluble markers because the water allows the components in the ink to adsorb to the filter paper which creates the chromatograms. To separate pigments in other types of markers or pens, different solutions would be needed.



Lab 1B: Aluminum Foil Lab

Procedure: We began by using a scale to find the mass of our aluminum foil (0.56g). Next, we measured the length (12.9cm) and width (11.4cm) of the aluminum foil to use in the formula volume=length*width*height. Then using the formula d=m/v and the given density (2.38g/cm^3) and mass, we solved for h and found the height of the aluminum foil to be 0.0016cm. Since the original question asked for the height in millimeters, we converted 0.0016cm to mm and got our final thickness of 0.016mm.

Data:
Mass=0.56g
Density=2.38g/cm^3

Volume-
Length=12.9cm
Width=11.4cm
Height=0.016mm

Lab 1A: Density Block Lab

Introduction: The purpose of this lab was to calculate the mass (amount of matter in an object) of a I given plastic block using a given density and a calculated volume. The density (amount of mass over per amount of space) was given on the block while we calculated the volume (amount of matter an object can hold) of the block using the formula length*width*height=volume. To achieve accuracy, the goal was to have a percent error lower than 2% after discovering the actual mass.

Procedure: The materials used in this lab include: calculator, scale, ruler, and various plastic blocks.
 Steps:
1. Record the given density of the plastic block
2. Measure the sides of the block (in cm) using a ruler and record lengths
3. Find the volume of the block using the formula L*W*H=volume
4. Calculate the experimental mass of the block using the formula M=V*D
5. Use the scale to find the actual mass of the block
6. Calculate percent error using the formula ((actual-experimental)/actual)*100%=% error
7. If percent error is above 2%, repeat steps 1-6 again

Data:

Calculated (Experimental) Mass	Actual Mass	Percent Error
66.3g	67.8g	2.21%
94.3g	97.3g	3.08%
60.1g	63.3g	5.06%
35.5g	37.2g	4.57%

Conclusion: We were not able to reach the goal of a percent error below 2% and the most possible error of the lab was human error. After my lab partner and I were unable to successfully have an accurate mass after the first attempt, we quickly reached for another block and tried to speedily finish the lab to proceed to the next lab. Our frantic attitude to finish resulted in more inaccurate masses and our percent error increased higher and farther from 2%. I have learned that it is more important to attain accuracy rather than time. In the future, I will make sure to keep a steady pace in order to finish a lab with a successful and accurate result.