Stoichiometry Problems

Here is a picture of the notes we took/ the worksheet we did last week in class when we were beginning to learn about stoichiometry:

These practice problems, along with the flow chart at the top have been really helpful to me while studying this unit, and hopefully they will be to others too. Here is a website that I found to explain more in-depth how to do the above problems: Stoichiometry

Calculating Percent Yield of the Aspirin Lab

Recently in class, we dug out some old information from the Aspirin Lab we did a while ago, and used it to apply to this unit by calculating the percent yield of the reaction from the lab. The balanced chemical reaction that we began with was:

C7H6O3(s) + C4H6O3(aq) --> C9H8O4(s) + C2H4O2(aq)

If you don't know how to balance a chemical equation yet, here is a website to tell you how: Balancing Chemical Equations

Next, we used the mass of the starting salicylic acid to determine the theoretical amount of the acetylsalicylic acid formed, and got 6.7110g C9H8O4

Lastly, we determined the percent yield of the reaction by using this equation:

Source of above picture

Here is a website explaining how to calculate this: Percent Yield

When I used the above formula to calculate the percent yield of the aspirin lab, I came up with 77.179%. 

How to Find Limiting Reagent

When trying to find the limiting reagent in a chemical reaction, there are two different methods you can use. 

Method One:

1. Determine the balanced chemical equation for the chemical reaction.

2. Convert all given information into moles.

3. Calculate the mole ratio from the given information. Compare the calculated ratio to the actual ratio.

4. Use the amount of limiting reagent to calculate the amount of product produced.

5. If necessary, calculate how much is left in excess of the non-limiting reagent.

Method Two:

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 reagent.

5. The reactant that produces a larger amount of product is the excess reagent.

6. To find the amount of remaining excess reactant, subtract the mass of excess reagent consumed from the total mass of excess reagent given. 

Here is a website that I found that uses the above methods to work through several examples: Finding Limiting Reagent

Here is another website that has practice problems dealing with this topic: Limiting Reagent Practice Problems

Copper II Chloride and Iron Lab Reflection

For a couple days during this past week in class, we did the Copper II Chloride and Iron lab. It was by far one of the coolest labs we have done thus far. On day 1, we roughed up an iron nail with steel wool and put it in a baby food jar filled with water and Copper II Chloride. We then let it sit overnight. Here is what it looked like in the beginning:

Here is what it looked like after I checked in on it later that day, after the Copper had begun to form and the solution changed colors:

Here is what it looked like the next day, when we came back to the lab and a lot more Copper had been formed:

We took the nail out of the solution and look what had happened to it overnight:

I did not expect anything like this to happen to the nail so quickly! The lab is still ongoing, as we still have to go back next week and weigh the Copper that was made from the reaction. Overall, this lab was really cool, and calculating the amount of moles of each substance made and the percent yield was educational and really good practice. Here is a website that I found that tells you how to do this same experiment, but using lemon juice as your solution instead, so you can do it at home: Coating a Nail With Copper 

Activity Series of Metals Lab

This past Tuesday, we did a lab about determining an activity series. We combined several types of metals and acids to see if they reacted. A lot of them did, and produced things like bubbles and gas and sometimes changed colors! Here are a couple pictures of what some of the reactions looked like:

After we recorded all the reactions that occurred, we determined our own activity series for the metals, based off of which reacted with the greatest amount of things. Overall, this lab was the most interesting one that we have done so far. I really enjoyed seeing all of the different things that could happen during a chemical reaction.

Types of Reactions

Last week in class, we learned about several different types of reactions to prepare for the unit test that we took on Thursday. The type that we spent the longest time learning about were redox reactions. This stands for reduction and oxidation. During this type of reaction, electrons are transferred from a metal to a non-metal. If a species loses electrons, it is oxidized and is the reducing agent. If a species gains electrons, it is reduced and is the oxidizing agent. A trick to help remember this is: OIL RIG, which stands for "Oxidized is lost. Reduction is gained." A more specific type of redox reactions are redox single-replacement reactions. During these, the metals have changed places and "the likes attack like". This type of reaction is based on reactivity series. Here is a link to a website that I found that explains everything you need to know about redox reactions: Redox Reactions

Here are the other types of reactions that we learned about:

-Synthesis: two or more reactants combine to form one product
-Decomposition: one reactant produces two or more products
-Combustion: a hydrocarbon reacts with oxygen and the products are CO2 and H2O

Here is a picture of examples of synthesis reaction equations:

Source of above picture

Reactions That Form Water

This past week in class, we learned about acid/ base reactions. The driving force of these reactions is water, and they always produce a salt and water as products. We also learned about strong and weak acid and bases:

Strong Acids:

-Produe H+

-Protonate completely 

-HCl, HBr, HI

-If oxygens outnumber hydrogens by 2 or more

Strong Bases:

-Contain an OH- anion

-Disassociate completely

-All group 1 and 2 metals and the -OH anion

Weak Acids:

-Don't protonate completely

-Not on the memorized list

-Parent present

Weak Bases:

-Don't disassociate completely

-Not on the memorized list

-Parent present

Here are some websites that I found that tell how to figure out if something is a strong or weak acid or base and some examples: 

-Strong and Weak Acids

-Strong and Weak Bases

Here is a picture of some common acids and bases:

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Solubility Rules Lab

This past Friday, in Chemistry class, we carried out a lab where we had to combine 10 different elements in a well plate and write down which ones reacted to form a precipitate. After we collected this data, we had to figure out the balanced chemical reaction equations and the balanced net ionic reaction equations for these. Before we conducted the lab, for practice, I went through all of the possible reactions and predicted whether or not they were going to produce a precipitate, using the solubility rules. Here is a website that explains how to do this: Predicting using Solubility Rules

Whenever two chemicals reacted to form a precipitate, they formed a unique color, and a lot of them were very surprising and cool! I did not know that two clear liquids could come together to form something so colorful. Overall, this lab was really fun to do, and it was really helpful in getting me to memorize the solubility rules. Here is a picture of some of the chemicals that reacted to form a precipitate:

Chemical Reactions

This past week in class, we started learning about our next unit, Chemical Reactions. You can tell when a chemical change is occurring thanks to sensory clues. These are things such as:
-color change
-a solid forms
-bubbles form
-heat/flame is produced or absorbed
Here is a link to a website that I found that has a list of chemical reactions that occur in our everyday life: 10 Chemical Reactions

In a chemical reaction equation, there will be a small letter(s) after each compound, telling you what state it's in. These are:
-g (gas)
-l (liquid)
-s (solid)
-aq (aqueous)

Here is an example of what one of these equations might look like:

Source for above picture

When you change the coefficient in a compound, it changes the amount of the element in it. When you change the subscript, it changes its composition and identity.

Here is an example of how to write out a balanced chemical equation:

-Methane reacts with gaseous oxygen to form gaseous carbon dioxide and water.
CH4 + 2O2(g) --> CO2(g) + 2H2O

Here is a helpful website that I found that explains this process more in-depth: Writing a Chemical Equation

Formula of a Hydrate Lab

 This Monday, we took a pre-lab quiz in order to participate in the Formula of a Hydrate lab. My partner, Kendall Kellerman, and I both managed to pass it and carry out the lab. To start it off, we put some crystallized hydrate into a test tube and recorded its mass. Next, we turned on the bunsen burner and held the flame up to the tube until almost all of the water in the hydrate had evaporated and it had turned white. Then, we recorded the new mass. While doing this lab, I learned a couple things:

1. Adding water back in to the anhydride is really cool looking, and it produces heat.

2. DO NOT ADD WATER BACK IN TO THE ANHYDRIDE. It becomes too hot to hold, and is almost impossible to get out of the test tube. Kendall and I know this from experience....

Here is the hydrate when we added the water back to it:

After completing the lab, I wanted to learn some more about how this whole process worked, so I found this website: Dehydrating a Hydrate

Weekly Quiz Reflection

Yesterday in class, we took our weekly quiz over the first half of the chemical composition unit. It had things on it referring to things like molar mass, percent composition, and hydrated compounds. Going into the test, I did not feel very confident at all. I had heard from other students that it was difficult, and I felt unprepared. However, our scores are in the grade book now, and I ended up getting a 15/17! Which isn't perfect, but I'll take it. Moving forward, and getting closer to the actual unit test, I now have a better idea of what exactly to focus on when I'm studying, and I know how some of the questions might be worded. The main thing I am going to focus on is learning how to calculate percent composition of compounds, because I didn't really know how to do that on the quiz.

Here is a link I found that I can use to help me learn about and study this topic for the test: Calculating Percent Composition

Here is another link that I found, and this one explains molar mass in a really easy way to understand: The Mole and Molar Mass

Converting Mass, Moles, and Molecules

The other day in class, we learned how to convert between moles in a balanced chemical equation, mass in grams, representative particles (atoms, molecules, formula units, ions), and the volume of gasses at STP. We were given the "Mole Road Map" to help with this, which can be seen below:

Source for the above picture

This map gives you the proper equations to use when converting, and when to use each of them. Here are a couple examples of problems that you can use the Mole Road Map on:

- How many grams are in 5.9 moles of Na?

(5.9 moles Na) x (22.99g Na/ 1 mole Na) = 140g

-How many grams are in 2.13 x 10^25 atoms of Platinum?

(2.13 x 10^25 atoms Pt) x (1 mole Pt/ 6.02 x 10^23 atoms Pt) x (195.08g Pt/ 1 mole) = 6.90 x 10^3g Pt

Here is a helpful website that I found that goes more in-depth as to how to convert in problems like the ones above: Mole conversions

Hydrated Compounds

Recently in class, we learned about a new topic: hydrated compounds. They have water molecules as a part of their chemical formula. These contribute to the crystalline structure of the compound, as seen below:

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Here is a website with an easy to understand, yet very detailed description of hydrated compounds: Properties of hydrates

Hydrated compounds are different than anhydrides, which were once hydrated.

Here are some examples of how to name hydrated coumpounds:

-CaSO4 x 2H2O = Calcium sulfate dihydride

-MgSO4 x 7H2O = Magnesium sulfate heptahydride

-FeCl2 x 4H2O = Iron (II) chloride tetrahydride

Here is a helpful website that I found that describes how the nomenclature of hydrated compounds works: Naming hydrates

When you heat a hydrated compound, it gets rid off the water in it, and changes the chemical structure of the substance and its appearance, as seen below:

Source for above picture

Significant Figures and Zeroes

Another topic we learned about recently in class are "sig figs"; this is short for significant figures. This is one of the more challenging topics of this unit, so I decided it would be a good idea to make a post about it, so if I need help reviewing/remembering how to use them, I can refer back to this.

Sig figs are the digits that were actually measured, and we pay close attention to them when rounding. When we estimate something using sig figs, we can estimate 1 digit past the calibration on the instrument. 

Take the number:   0.004004500

0.004004500= this zero before the decimal is not significant

0.004004500= these zeroes directly after the decimal are not significant

0.004004500= this 4 is significant

0.004004500= these zeroes stuck in between two numbers are significant

0.004004500= these numbers are significant

0.004004500= these trailing zeroes are significant

The above example shows the rule to follow when determining which numbers are significant. Here is a useful website that I found that describes these rules more clearly: rules for finding significant numbers

Here are a few more examples: 

123 = 3 sig figs

0.123= 3 sig figs

40.506= 5 sig figs

9,800. x 10^4= 4 sig figs

600.= 3 sig figs

4.5600= 5 sig figs

98000= 2 sig figs

The last thing we learned about dealing with significant figures was how to add/subtract and multiply/divide with them. Here is a great website that explains how to do this: adding/subtracting and multiplying/dividing sig figs

Chemical vs. Physical Changes and Properties

The other day in class, we learned about/reviewed chemical and physical changes and properties. Here is a brief outline of the most important things that I learned, that I think will be helpful to know for future tests/quizzes:

Physical Properties: can be observed without changing one substance into another.

-Boiling point

-Density

-Mass

-Volume

-Smell

Chemical Properties: can only be observed when a substance changes into another.

-Flammability

-Corrosiveness

-Reactivity with acid

Here is a helpful website that I found to explain the differences between the two in a more in-depth way: chemical vs. physical properties

Physical Change: changes in matter that don't change composition/identity.

-Change of state

-Change in temperature

-Change in volume

Chemical Change: result in new substances.

-Acid base

-Redox

-Double replacement reactions

-Burning

Here is a helpful website that I found to explain the differences between the two in a more in-depth way: chemical vs. physical change

Make-a-Mole Reflection

This past Friday, we celebrated National Mole Day in Chemistry class, which is explained here: "What is National Mole Day?". We all sewed moles, brought them in, and had a party. I spent several hours spread out over several days creating my mole. I cut out lots of colorful 2x2 inch squares, then sewed them all together to make patchwork fabric to make my mole out of.

Above photo was taken by myself

After lots and lots of cutting, pinning, sewing, and stuffing, my mole was complete!!

Above photo was taken by myself

This project was fun and I really loved seeing everyone's finished products and how creative they were. It also helped improve my sewing skills!

Aspirin Lab Reflection

The week before we went on fall break, we took a pre-lab quiz to see which groups would get to participate in the aspirin lab. My partner and I were the only ones out of the Day 2 groups to pass it and get to carry out the lab. This was rewarding, because I took time to thoroughly study the lab before-hand, and it paid off. The first thing we did was combine all of the different chemicals in a flask:

Above photo was taken by myself

After several more steps, the chemicals were put into a beaker and we heated it up:

Above photo was taken by myself

When we came back to the lab the next day, the aspirin crystals had formed:

Above photo was taken by myself

After we drained all the water out and transferred the crystals out of the beaker, this was the finished product:

Above photo was taken by myself

Overall, this aspirin lab was fun yet very educational, and I got to experience using several chemicals and pieces of equipment that I have never used before, so I learned a lot.

After I completed the lab, I wanted to learn more about aspirin and the chemicals/methods used to make it, so I did some research. Here is a very insightful website that I found to help with my curiosity:  more about aspirin

Unit Test Reflection

Today in class, we took the Atomic Structure and Radioactivity unit test. Luckily, it was not as bad as I thought it would be, and I think that is partially thanks to the blog posts I have made this unit. I actually used them as a resource while studying, and they were very helpful. However, there were still a couple things that I was confused about on the test:

-How to calculate the percent abundance of one isotope atom when you are given the individual masses and the amu of the element

-Which type of radioactive decay can penetrate the human body the furthest

To help me learn about the above questions for future exams, I researched each of them. Hgere is a link I found giving the answer to my second question:

Strength of Radioactive Decays

Overall, I knew most of the material on the test, thanks to these blog posts, and I will be sure to keep it up, in order to continue doing well on the tests.

Half-Life

Recently, in class, we learned about half-lives: their meaning and how to calculate them in real-life examples. Half-life is the time it takes for half of a sample to decay into a stable form. Here is a link to a helpful website that goes more into depth on what a half-life is and relates it to radioactive decay:

Half-Lives Explanation

Here are a couple examples of problems dealing with half-lives that I might see something similar to on a test:

Q: How much of a sample of Uranium with a mass of 150 grams is left after 7 half lives? 

A: 150/(2^7)= 1.17 grams

Q: Radium-225 has a mass of 2.59 grams and decays for 135 days. What was the mass of the original sample?

A: 135 days x 1HL/1.5 days = 9 HL passed

(2.59g)(2^9)= 1326.08 grams

Q: The half-life of radium-255 is 15 days. What percentage of radium is left after 3 months?

A: 3 months x 30 days/1 month x 1 HL/15 days = 6 HL

1=50%

2=25%

3=12.5%

4=6.25%

5=3.125%

**6=1.5625%

Overall, this post will serve as a great resource to look back at when I have to solve half-life problems, because the three examples above accurately represent and explain all of the different types of half-life questions that I will probably see on tests or class work. 

Radioactive Decay

Many nuclei are radioactive. This means that they spontaneously decompose to form a new nucleus and produce one or more particles. These nuclear reactions are shown by using a nuclear equation. It shows the radioactive decomposition of an element. Here is an example of some nuclear equations:


Source of picture

There are three different types of radioactive decay. The first is alpha decay, which produces alpha particles, that are helium nuclei. The other two types of radioactive decay are beta and gamma decay. Beta decay releases beta particles, which are electrons. Gamma decay releases high energy forms of light called photons. Here is a link to a website that explains all three types of decay, and how to calculate them:

Radioactive Decay

Overall, radioactive decay is a relatively easy concept to understand, and using this blog post to reflect on throughout the rest of the unit will help me retain all of the information on this topic that I learned in class.

Beanium Lab Reflection

This week, on Wednesday, our chemistry class did a lab about an imaginary element named "beanium". The purpose of using this imaginary element was so we could see it with the naked eye, since it is macroscopic. To carry out the lab, we counted the number of atoms of each isotope present, and then used an electric scale to find the total mass of each isotope. We also found the average mass and the percent abundance of each isotope. Then, using previous knowledge and the formula that we learned a couple days before, we calculated the average atomic mass of beanium. The formula we used is explained on this website:

Average Atomic Mass Equation Explanation

This lab helped me understand how to find all of the values of isotopes I listed above, because we were able to actually physically see and touch the "atoms". Overall, this was a fun and enlightening lab, that will help me in the future, when I have to calculate the same thing with real-life isotopes.

Here is a picture of the beanium atoms, while we were sorting/counting them:

Source of picture: taken by myself

Mass of Subatomic Particles

Here are some important things that I learned today in class to remember about the mass of subatomic particles:

                        Relative Mass:      Relative Charge:
Electrons:            1                                   1-
Protons:           1863                                 1+
Neutrons:         1839                               none

Isotopes:
-Proton= an elements identity and mass
-Electron= an elements reactivity
-Neutron= an elements mass and isotope determination

There are two ways that the mass number and atomic number of an element may be presented:


Source for the above picture



Source for the above picture

Half-Life Calculation

After taking and reflecting on the Atomic Structure and Radioactivity pre-test, I decided my first focus for this unit would be calculating half-life, since I already have a general understanding of it. This will help me learn it quickly and be able to move on to the more challenging topics in this unit. After doing some research, I found this helpful diagram that shows an example of half-life decay, by illustrating the decay of 544 grams of a substance that has a half-life of 1 day:

 Source for the above picture

Doing research about half-life lead me to discover that there are three different types of half-life decay: zero, first, and second order reactions. The equation that you use to calculate half-life differs depending on the type of reaction. A very useful website to help me remember how to calculate each type is:

How to Solve Half-Lives 

Pre-test Reflection

In chemistry class today, we took a pre-test over atomic structure and radioactivity. I knew very little, but I was surprised that I actually did know how to calculate the answer to a couple of the half-life questions. I remember this information from past science classes such as Earth Science. Some of the things I have never learned about before include all the different types of radiation and decay. I recognized the terms, but did not know what they meant. Throughout the next three weeks, during this unit, I hope to learn these terms and how to apply them to solve problems, so that way I can be much more successful on the actual unit test, compared to this pre-test. After the test, I did some research about some of the questions that I saw on the test, and I found some websites that might be helpful to look back on during the unit. You can find them here:

- Types of Radiation

- Types of Decay


Also, here is a very helpful picture to illustrate the penetrating powers of the different types of radiation:


Source for the above picture

Frontier Chemistry Project

Doing the Frontier Chemistry Project was very educational and practical. I now know how to treat myself if I was in the wilderness and got hurt. I know how to identify medicinal plants and how to prepare and apply them. Also, lately, while just driving down the road, I have been able to name several of the plants that I have seen. So overall, this project was very useful and also helped me apply chemistry to the real world.

Polyatomic Ions

During the nomenclature unit, I successfully memorized all 22 polyatomic ion names and their matching formulas. I was able to accomplish this by making flashcards and reviewing them many times, alternating which side of the card I looked at. Knowing these ions off the top of my head is very useful when it comes to naming acids. Also, we will be using the polyatomic ions throughout the whole entire rest of the year, so having all of them memorized will be very helpful.


Source of the above picture

Introduction Page

Hi, my name is Carly Dobert. I am 16 and a junior in high school. I have a younger brother, an older sister, and two cats. At school, I am involved in National Honor Society, FBLA, and French Club. I like watching Netflix, sleeping, and hanging out with my friends in my free time. I love all food, but my favorite food is ice cream. My favorite color is purple, my favorite animal is a Zebra, and my favorite music artist is Twenty One Pilots. After high school, I want to attend Duke University and earn a degree in Zoology.