Chemistry Honors Lab: Titration

Lab: Titration

This lab's purpose was to practice our titration skills and calculation skills.  During the lab, my group and I titrated acetic acid and sodium hydroxide with 4 drops of phenolphthalein to visually signal when the equilibrium point just past.  Then we take notes on how much NaOH was used and how much acetic acid was used.  Using that and the given pH of vinegar (2.41) we were able to calculate the percentage ionization.  For this reaction, the percent ionization was 0.44% and the reason for this is that acetic acid is a relatively weak acid and sodium hydroxide only has one ionizable proton.  This percentage was calculated by dividing the molarity of H3O+ (.0039) by the molarity of acetic acid (.885) and then multiplying by 100.

Set Up

Titrated Solution

Chemistry Honors Lab: Chicago River Water Testing

Chicago River Water Testing

My group tested the nitrate levels of the Chicago River, about a one mile from Lake Michigan.  The test consisted of 50 mL of river water and two pre-made mixtures added to the sample.  These mixtures' purpose was to react with the nitrates and create a a pink color for the tester, in this case me.  The more intense this pink color, the more nitrates there were in the water.  If there are too many nitrates in the river, it may cause eutrophication.  High amounts of nitrates in drinking water could also lead to many problems in very young and unborn children, such as infant methemoglobinemia.  Two groups did this test, and the average "Q" value, or quality value, of the river was 100, meaning that water has perfect nitrate levels.  One way I or anyone could continue this great balance is to ensure that there car and its engine is working properly and that there is no chance of leakage of any fluid.

3 Things I Learned

1) Due to the near perfect balance that the bridge achieves, there are surprisingly small motors used to lift the Michigan Avenue bridge.

2) It took 12 years to build the Michigan Avenue bridge.

3) Chicago Sanitary District was established in 1887

2 Surprising Facts

1) The river flow was reversed to avoid polluting Chicago's main source of drinking water with its inhabitants' sewage.

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2) 2/3 of the men died when working on the canal in 1839-1839

1 Question

1) Whose idea was it to name 5 consecutive streets after the Great Lakes?

View from Michigan Ave. Bridge Mueseum

Color comparison to find nitrate levels

Chemistry Honors Lab: Calories in Food

Lab: Calories in Food

This lab was conducted to find calories in many nuts, ours being the brazil nut.  We did this by lighting a brazil nut on fire and heating a beaker with 50 mL of water and measuring the before and after temperatures.  

Questions

1) Did you measure a temperature change in the food sample or the water?

The water

2) Did you measure the energy released by the food sample or the energy gained by the water?

The food sample (brazil nut)

3) What happens to the small amount of energy that is not absorbed by the water?

That energy was absorbed by the the tin can propping the beaker above the flame.

4) Were you surprised by any of the results?  Explain

I was pretty surprised by how much energy was packed into that singal nut.  I never really thought of Calories in that way, I just thought that I need about 2000 of them everyday.  But now I have an image I can look back on to reflect on what the Calorie is in actuality.  

Chemistry Honors Lab: Specific Heat of a Metal

Lab: Specific Heat of a Metal

This lab was set up to find the specific heat of a metal by measuring the rise of temperature in a water bath that surrounded a heated sample of an unknown metal.  After taking measurements, we found the specific heat via the collected data and compared it to the known specific heats of a couple metals.  Our calculated specific heat was 894 J/kg oC.  This was closest to aluminum's specific heat, which in 901 J/kg oC.  This identification makes sense due to the the shinny silverish color the sample had.

Metal heating in water bath

Measuring the water temp with the metal sample

Chemistry Honors Lab: Evaporation and Intermolecular Attractions

Lab: Evaporation and Intermolecular Attractions

2) Explain the differences in the difference in temperature of these substances as they evaporated.  Explain your results in terms of intermolecular forces.

The five substances we tested were: Methanol, Ethanol, n-Butanol, Glycerin, and Water.  All of these substances have their strongest intermolecular force being hydrogen bonding.  Of the five, though, Methanol changed the most in terms of temperature, going down a total of 14 degrees Celsius.  We believe that this major change of temperature is due to the high volatility this substance has.  This is caused by the fact that the molecule has only one potential hydrogen bond to form with another molecule.  The one site where potential hydrogen bonds can form is relatively low if compared to other the other substances.  The next largest drop in temperature was Ethanol which 6.3 degrees Celsius.  Ethanol, similarly to methanol, only has one site for a possible hydrogen bond to form with a similar molecule.  The reason why there is a 7.7 degrees difference between the two is due to the increase of the molar mass.  Ethanol has a molar mass of 45.04 grams and methanol has a molar mass of 32.04 grams.  The molar mass of ethanol means that the molecules themselves are heavier, and therefore require more energy to change its state of matter, leading to less molecules evaporating.  The change in temperature for water was -4.3 degrees Celsius.  Water, having two sites for potential hydrogen bonds to form with other molecules definitely has something to do with the 2 degrees difference in change when comparing water to ethanol.  The next substance is n-Butanol, with a change of -2.0 degrees Celsius.  n-Butanol, having only one site for possible hydrogen bonding, would commonly be thought to have a higher change in temperature, but this is not the case.  My partner and I believe it is due to the huge molar mass when compared to water; n-Butanol with 74.04 grams and water with 18.01 grams.  Finally, the last substance tested was glycerin.  The change in temperature recorded was not what was expected.  The change was +1.6 degrees Celsius.  After this result, my group can upon the conclusion that since glycerin has three sites for possible hydrogen bonding and has a substantial molar mass of 92, that the cooler temp. inside the beaker and the warmer temp. in the lab over came the evaporation cooling effect.  This was most likely due to the lack of said evaporation.

3) Explain the difference in evaporation of any two compounds that have similar molar masses.  Explain your results in terms of intermolecular forces.  

Methanol and ethanol have the two closest molar masses in the experiment with a difference of 13 grams, but there difference in temperature was among the largest being 7.7 degrees.  Even though both substances only have one site for hydrogen bonding to take place, the extra carbon atom and two hydrogen atoms where enough to alter the results.  This is most likely due to the idea of London Dispersion Forces.  The extra carbon and hydrogen atoms bring electrons with them as well.  The more electrons in a molecule, the more of a possibility that a slight change in distribution could occur.  The change in distribution could have effect on the overall polarity of the molecule and this has a ripple effect throughout the substance.  The increase in the chance for an intermolecular force to occur causes the evaporation rate to decrease because the substance with more intermolecular force requires more energy to change its state of mater.

4) Explain how the number of -OH groups in the substances tested affects the ability of the tested compounds to evaporate.  Explain your results in terms of intermolecular forces.  

The more -OH groups in the substance, the less it will evaporate.  This is due to the fact that hydrogen bonds are difficult to break.  The more -OH groups there are, the more potential hydrogen bonds there are for that substance.  With these two things in mind, one can come to the conclusion that the more -OH groups there are, the more hydrogen bonds can form, which means that there has to be more energy to change its state of matter, meaning it is less likely to evaporate.  

Chemistry Honors Lab: Electron Configuration Battleship

Lab: Electron Configuration Battleship

This "lab" was a game of Battleship but instead of placing your ships on a grid, you place them on the periodic table and instead of calling coordinates for your opponent to find, you would call out the elements using electron configuration notation.  The biggest struggle I encountered while playing was accurately communicating with my opponent.  The game's purpose was to practice using this newly learned skill, but it was still annoying at times.  I learned, through this game, that in chemistry, there are many different ways to communicate similar things.  Some methods might share more insight on specific details on certain topics, but these ways all can signify a certain element.

Picture of Battleship Set Up

Chemistry Honors Lab: Flame Test

Lab: Flame Test

In this lab, my group and I burned wooden sticks that soaked up many chlorine compounds over a bunsen burner.  Different chlorine compounds produced different shades of light.  We were to compare the results of the known compounds with two unknown substances and predict what they were.  My group decided, that since Unknown #1 had a red shade that the substance we strontium chloride.  We also determined that since Unknown #2 had a light lavender shade that the substance was potassium chloride.  Below are the answer to the pre-lab questions.

1) What is the difference between ground state and an excited state?

The ground state is when the electron configuration of an atom/element are in it's most stable and lowest energy state.  The excited state, on the other hand, is when the electron configuration is unstable and electrons are higher in terms of energy and will eventually calm down and return to the ground state.

2) What does the word "emit" mean?

Emit means that something, whether it be a photon or any amount of energy, is being created and dispersed away from it's source.

3) In this experiment, where are the atoms getting their excess energy from?

In this case, the "excess energy" is coming from the flame created by the bunsen burner.

4) Why do different atoms emit different colors of light?

Electrons, when heated, jump up to higher energy levels, but they don't stay there for long.  When they fall back down, they release their energy as photons.  For every element, the "quantized" amount of energy to go from one level of energy to the next is different.  That amount of energy determines the color of the light emitted.

5) Why is it necessary for each station to have separate wooden splints for each individual flame test?

After using on splint, the wood would be "contaminated" with that solution.  If we were to try and resoak that splint, the results of the following test would be skewed.  The reason being is that we wouldn't know which element is reacting.

Flame produced by Copper Chloride (CuCl₂)