pH Lab

In this lab, we created a spectrum using cabbage juice. First, we created a controlled variable with just the cabbage juice, and we set aside 6 other test tubes for the acids and bases.

The control variable was a pH of 7, and was a light purple color.
For the acids, we had 3 different tubes
tube number 1 had 5 drops of HCL added, with a pH of around 3 and was a red color.
Tube number 2 had 4 drops of HCL added, with a pH of 3-4 around, and was a red-pink color
Tube number 3 had 3 drops of HCL added, with a pink-violet color, and had a pH of 4

For the bases, we had 3 different tubes
For Tube number 5, it had 10 drops of NaOH added, and it was a yellow color, with a pH of 12
For tube number 6, we added 12 drops of NaOH and it was a lime green color, with a pH of around 12-13
For tube number 7, we added 14 drops of NaOH, with a dark green color, with a pH of 13






4. Which drops (acid or base) caused a more dramatic change in the pH of the solution? Why?

In my opinion, the drops of bases caused a more dramatic change in color. I thought this because it already had a natural purple color, the change from purple to yellow is more dramatic. I think the change from purple to pinkish-red is less of a change. This change from the purple to the yellow color was a bigger change because it completely changed the entire color of the spectrum for example. I think this makes sense because of the already dark color of purple, adding the base of NaOH would have more of an effect of the color change. I think that this change was more dramatic just because of the already dark color of the purple cabbage juice. If the starting color was a lighter color, for example, red, I think that the acid would make a more dramatic change because it would become a dark red, but in this case, I think the base change was more dramatic. I think if the starting color was less of a factor, this experiment could have been easier to see which effects a neutral more; acid or base.

5. What did I learn?
I learned a lot from this lab. I learned about the whole acid vs. base idea, and how each of these acids or bases effect each of the neutral pH colors. I learned about how the pH is affected, specifically by acids and bases, or HCL and NaOH. I also learned about adding acids and bases to neutral solutions, and that it often takes a lot of a certain acid or base to create a bigger change in color. For example, we had to add a lot of the NaOH to create a distinct change between the others. At first, we added around 3, 4, or 5 drops of the NaOH but these colors were not really any different. We later had to add a lot more of the drops to get a real change between the different test tubes.

This is my interpretation of the graph of this lab. I used the pH as the x variable and put the (0,7) variable in as well.

Also, you may notice the Our own experiment sign. This specific beaker was when we tried to add bases and acids together into one test tube to see the color. I believe that we added too much base because it ended up being a yellow color, similar to the other bases. We also tried to create different colors like blue and we created this by adding the base and more cabbage juice to get a blue color. I think this makes sense because the already dark color of the cabbage juice often overwhelms the base or acid colors. 

Here are some more pictures. Here is a picture of the pH scale for reference, along with some pictures of our clean lab table. Here are more pictures 

In this lab, we measured the pressure in the popcorn kernels. The popcorn kernels have water inside them, and when the water boils and has a lot of pressure, then it pops and becomes popcorn. First, we weighed all the measurements.

2.34 grams of water for 5 mL of water
30 kernels in total which was 4 grams in total
water displacement with kernels- 4.8
final weight- 118.5 including all the popped kernels
before popping 120.5
20 kernels popped, 10 did not.

4.8 divided by 30 is .16 and multiplied that by 20 is 3.2 mL.

then I took the 2 grams of the mass of H20 loss and found that that was.11 moles H2O

then I took the PV=nRT formula so
(.11 mole h20)(498 K)(.0821)
over 3.2 mL for the volume

with this equation, I got 1.45 and that divided by 20 of the number of kernels popped is .07 which I am sure is incorrect.

6. I think all the kernels did not pop because it got too hot. Most of the kernels, as you can see in the picture above that, did not pop looked like they were burnt, rather than popped. I think we may have used too much oil, or the oil was not evenly distributed so some of the kernels popped and others did not.
7. Obviously, something went wrong with our calculations because we got .07 atm per each kernel. I think it's because a lot of the popcorn pieces we counted as "popped" were not really popped, and were more of just bigger pieces than the kernels. I think also the moving of the bunsen burner could have affected the end result because there was an uneven distribution of the heat produced by each kernel. There also could have been a lot of miscalculations on the weight of the products, or the kernels could have been just bad.

I think if I were to do this assignment again, I would use different kernels and be a lot more precise with all the measurements. I would measure with a digital scale, rather than a 3 beam balance scale. I would use a more precise amount of oil and be more even with all the fire with kernels. I would also try out different numbers with the number of kernels. I would also try to be more precise with the counting of the kernels and the ones that did not pop.

In this experiment, we tested the pressure caused by mentos and diet coke. First, we took an empty bottle of coke and cut in half, to create a base or launch pad. Then we took a paper clip and put 5 Mentos onto the paper clip, and put that onto a cork. Then we went outside and put the cork with the mentos on top of the coke bottle. then we flipped over the coke and it created a rocket.

Why?
Due to gas laws, and the pressure we created, it created a huge explosion, making it look like a rocket. This is a process called nucleation, where a large amount of carbon dioxide in the diet coke is attracted to the Mentos, causing an immense amount of pressure, thus causing it to explode. Because we put a cork on top of the bottle, the pressure increased greatly. Because the also flipped it upside down and had a base, it was able to fly higher. The Mentos sank because they are fairly dense, and then quickly created bubbles. Low surface tension also helped the bubbles to grow faster. Diet coke works better than normal Coke because it is lower than in sugary water, creating a better rocket.

Gas Laws:
Due to Henry's Law, P=Kc. the p=partial pressure of the gas, K is the constant, and C is the molar concentration of the solute. This is why sodas fizz when you open them. The bubbles form in liquids due to the dissolved gas, and it is easier to form in soda than water. A nucleation site is always needed to form bubbles.

What went wrong?
I think the main reason this went wrong was the weight of the 2-liter bottle of coke. This was a lot of weight for only 5 mentos. We should have either have smaller bottles of coke, or more mentos in the bottle. We could have had two paper clips of mentos and a smaller bottle of coke and it would have flown much higher. Both of these would have increased the pressure, and decreased the weight, thus making it fly higher. Other factors such as temperature, angle, and inproper cutting could have also effected this procedure.

Limiting Reactant Lab

Analysis questions
1. What are the limited and excess reactants for each flask? How did you determine this?

The limited reagent was the baking soda for the flask with 1 and 2.5 grams of baking soda. For the flask with 4 grams of baking soda, and our own personal experiment, the vinegar was the limited reagent. Below is my work for finding what each limited reagent is. I found that for the flask with 1 and 2.5 grams of baking soda, this was less than the controlled variable, meaning that the baking soda was limited.

2. How is the amount of product in a reaction affected by an insufficient quantity of any of the reactants?

If a reaction has a limited quantity, it will not be able to completely finish it's reaction. When there is a limiting reaction, the end result will be heavily affected due to the limiting reactant. They results will not be accurate or precise due to the lack of true experimental values.


3. Which balloon was the largest? Explain.

The largest balloon was our personal experiment. We filled a balloon with the rest of the baking soda, which was around 10.75 grams of baking soda, with a radius of 6.37. This was the biggest, but the biggest balloon from the actual experiment was the balloon with 4 grams of baking soda, with a radius of 5.57.


4. Which balloon was the smallest? Explain.

The smallest balloon was the green balloon, the one with the least amount of baking soda. This one had 1 gram of baking soda, and reacted with the least amount of time. This had the least amount of baking soda, which meant is had the least amount of carbon dioxide in the balloon. It's radius was 2.47.


 5. Rust is produced when iron reacts with oxygen. How many grams of Fe2O3 are produced when 12.0 g of iron rusts?

4Fe(s) + 3O2(g) → 2Fe2O3(s)

It forms a total of 17.2 grams. My work is pictured above.



6. What real-life applications can this concept of limiting and excess reagents be applied to?

Limiting and excess reactants can be applied to real life because when certain items are limited, it affects the goal you are trying to attempt. For example, if your energy is limited, then the rest of your day will be affected due to the limited reactant.