Ideal Gas Law

Note: Pressure must be in atm, volume must be in L, and 

temperature must be in K. The constant R is .0821 L atm/ mol K. 

Modeled on the Kinetic Theory of Gases which has 4 basic postulates:

• Gases consist of molecules which are in continuous random motion
• The volume of the molecules present is negligible compared to the total volume occupied by the gas
• Intermolecular forces are neglibible
• Pressure is due to the gas molecules colliding with the walls of the container

Example: Calculate the volume (L) occupied by 7.40 g NH3 at STP. 

First, list the knowns. 

• V= ?
• T=273.15K
• P= 1.00 atm
• n= 7.40 g x (1 mol/17.04g) = .434 g
• R=.0821

Then, plug in the values into the equation to solve for V. 

• PV=nRT
• 1.00V=.434 x .0821 x 273.15
• V = 9.73 L 

Ideal Gas Law Video

Common Units of Pressure

All of these need to be memorized. Note that the values with the word exactly by them have an infinite number of significant figures. 

Charles' Law

    In Charles' law, pressure and moles are held constant which gives us the formula:

Note: Temperature must be in Kelvin

Example:

     A sample of gas at 15 degrees C and 1 atm has a volume of 2.58L. What volume will this gas occupy at 38 degrees C and 1 atm. 

First, start by listing the known variables. Pressure stays constant, so we do not have to worry about pressure in our calculations. 

• T1= 15 degrees C--> 15 + 273.15 = 288.15 K
• V1= 2.58 L
• V2= ?
• T2= 38 degrees C--> 38 + 273.15 = 311.15 K

Then, plug in the variable into the equation to solve for V2

• V1 x T2 / T1 = V2 
• V2 = (2.58 x 311.15) / 288.15
• V2= 2.79L

Other Gas Laws:

• Boyle's Law
• Avagadro's Law
• Dalton's Law

Air Bag Lab

     Today in class, we had to determine the moles of baking soda and mL of vinegar that would create enough CO2 gas without bursting the bag as a result. Below is the procedure for how we did so.

1. Fill a graduated cylinder with a known amount of water and then pour into the ziplock bag. Repeat this until ziplock bag is full. This value is the volume of the ziplock bag. 

1. Record the pressure and temperature of the room. We were told the temperature was 21 degrees C and the pressure is 29.06 inHg. Then, convert temperature and pressure to Kelvin and atm respectively. Calculaions are shown below.

     3. Use PV=nRT in order to find the moles of CO2. There is a 1:1 molar ratio, so the moles of                  CO2 needed is equal to the moles of NaHCO2 (baking soda). 

     4. Once the number of moles of baking soda and vinegar are found, convert each to g and mL                  respectively. 

Video of a Similar Lab

Flowchart

Below is the flow chart used to determine intermolecular and intramolecular forces:

Hint: If the bond is ionic, the bond contains ions. If it does not, it is covalent.

Example:

KBr contains ions --> No polar molecules --> Ionic bonding 

Helpful links:

• Intermolecular vs intramolecular forces
• How to tell if a molecule is polar
• Ionic or covalent?
• Intermolecular forces practice quiz

Phase Change Diagrams

Pressure and Temperature

• Triple point- point at which the solid, liquid and vapor states that all have the same vapor pressure coexist
• Critical temperature- the temperature above which the vapor cannot be liquefied regardless of the pressure applied
• Critical pressure- the pressure required to liquefy the vapor at the critical temperature
• Critical point- point at which the critical temperature and critical pressure coincide

Temperaure

 Helpful links:

• Phase diagrams
• Phase diagrams video

Biodiesel Video Project

     We have started filming our project for the biodiesel project! Our video is going to be my partner drawing on a white board with voiceovers explaining the benefits of biodiesel. It is not a super creative concept, but neither my partner or I are very creative and with the tight deadline, we did not want to try and do something completely out of the box that may fail miserably. Also, both of us are not advnaced with using iMovie, the editting program we are using, but it is fairly easy to figure out as we go along. Below is a snippet of the opening of our video.

Tips for iMovie

Biodiesel lab

     We made our own biodiesel in lab today. We did this by taking dirty oil from a fast food restaurant and mixing it with a base solution. We let the solution sit overnight and let the contents separate into the two distinct layers seen below. We then took a micropipette and slowly placed our biodiesel into a separate cup which is seen in the third picture.

Biodiesel after separation

Leftover biodiesel

Our biodiesel and biodiesel candle

Biodiesel Project

    Today we started our initial research of biodiesel. I did not know much about this topic, so I found the research interesting. Who knew all of the benefits to using biodiesel?

Below are links to some websites we found useful to our research:

• Alternative Fuels Data Center
• What is biodiesel?
• How is biodiesel made?

About the contest

Night Before the Test

     I feel like I have prepared well for the test because I have reviewed notes and completeted the practice tests and worksheets available for test prep online. I feel like I am extra worried about this test because there is no quiz, so this test will make an even larger impact on my grade. I feel like tomorrow should not be that bad though. Hopefully I am not proved wrong.

For those still needing to study, check out the links below:

• Formal charge practice
• Drawing lewis dot structures
• Resonance structures
• Molecular shape and geometry
• Molecular shape and geometry practice quiz
• Bond polarity

Bond Polarity

     When a bond between 2 or more elements is formed, there may be a slight pull of the electrons in the bond toward the more electronegative element which results in a polar molecule. Today we learned how to determine whether or not a bond is polar.

     In the molecule above, flourine (F) has the greatest electronegativity which can be found on the periodic table. Because of this, the electrons are pulled toward it and cause an unequal distribution of charge. F has a slightly negative charge as noted by delta minus because is has to negatively charged electrons closer to it. This unequal distribution in charge causes a dipole moment, which is represented by the arrow above the molecule as shown above, The dipole moment points towards the more electronegative atom. In a molecule containing a single bond is automatically polar if it has a dipole moment, like the HF molecule shown above. Dipole moments do not always mean polar in molecules involving multiple bonds, however.

     For example, the CO2 molecule contains dipole moments but is not considered polar. The oxygens are the more electronegative atoms, so the dipoles point outwards. These 2 dipoles are in the completely opposite directions, so they cancel each other out, making the molecule nonpolar. 

Modeling Lab in Library

Shown above is the HNS, lewis dot structure, and 3D molecule SF4

     Today our class met in the library to do an activty that would help us better understand how to draw lewis dot structures using the have need share model and how to buid these molecules in 3D. Also, this lab gave us practice with determining the shape and geometry of a molecule. I enjoyed this activty because I like working hands on and getting to use the dry erase tables was fun. I am happy we did this lab toward the beginning of the unit because it really helped us get the basics down before moving onto more difficult concepts.

Unit Test

Overall, I feel like I  did well on this unit's test. I knew the material well, but there were a lot of questions to answer within the hour, so I did not have time to work some math problems or double check any of the answers I was unsure about. Hoping for the best.

Time Management During Tests

Quantum Numbers

There are 4 quantum number for each specific electron.

1. Principle Quantum Number
2. Angular Momentum Number
3. The Magnetic Quantum Number
4. The Spin Quantum Number

Practice Quiz

Ionization Energy vs Electron Affinity

     Ionization energy is the energy needed to remove an electron from a gaseous atom. The first ionization energy is the energy required for removal of the first electron. Electron affinity, on the other hand, can be thought of as the ease with which an electron may be added to an atom, creating an anion. They are essentially opposite in definition, but they both increase as you move and up and right on the periodic table.

Sublevels

There are four different sublevels: s, p, d, and f.



Note: Do not forget helium, an element in the s-block, that is hidden in the p-block.

Unit Quiz

Last week we took our weekly quiz for this unit and it went well. I got a grade that is lower than what I had hoped, but it was still higher than most of my other quizzes. After having got the quiz back, I release all of my little mistakes and where I went wrong. I will hopefully not make similar mistakes on the upcoming unit test. This unit seems like a lot of memorization, so maybe that is why I am doing better than many past units.

Rules for Placing Electrons

There are three basic rules for placing electrons. They are listed below:

1. Aufbau Principle: electrons enter orbitals of lowest energy first.
2. Pauli Exclusion Principle: an orbital can only contain two electrons with opposite spin.
3. Hund's Rule: within a sublevel, electrons enter singly before pairing up

Strong Acids and Bases

List of Strong Acids:                            monoprotic acids*

• Perchloric acid
• Chloric acid
• Hydrochloric acid*
• Hydrobromic acid*
• Hydriodic acid*
• Nitric acid 
• Sulfuric acid

Remember: Strong acids contain oxygens that outnumber the hydrogens by a ratio of 2 or more and protonate completely to produce H+ ions when placed in a solution.

Strong Bases:

    Strong bases are those that contain the hydroxide (OH-) ion plus a group one or two element. Just like strog acids, they dissocitate completely when placed in an aqueous solution. 

Helpful Links:

Identify Strong and Weak Acids and Bases Practice Quiz

Acids and Bases Practice Quiz

Determining pH and pOH

Use this box to go to and from hydriounium and hydroxide concentrations to pH and pOH. Just follow to arrows you need and use the functions on them. Examples are shown below.

Example 1

     What is the pH of a soultion that is 12.5 M HCl?

The problem gives us molarity of a strong acid, so that is the number we use for the [H+] concentration. We want to go from [H+] to pH, so we use the negative log function. 

-log[12.5]= -1.097

The substance has a pH of -1.097.

Example 2

What is the pH of a solution that has 8.95 M NaOH?

The problem gives us molarity of base, so we use this number for the [OH-] concentartion. This problem is a two step problem in which we can go from [H+] concentration to pH or pOH to pH. You will come out with the same answer either way.

Way 1:

Way 2:

Helpful links:

What is a Logarithm?
pH vs pOH

pH Scale

Pictured above is the pH scale. It is used to determine if a substance is an acid or a base. Substances with a pH less than 7 are acidic. Substances with a pH over 7 are considered basic. Substances with a pH of 7 are neutral. Remember, it is possible for a substance to have a pH less than 1 or greater than 14.

pH's of common substances

How to Tell if a Salt is Acidic or Basic

   When an acid- base reaction occurs, the products are a salt and water. The salt will be composed of the cation of the base and the anion of the acid. The determining factor of the strength of a salt is the strengths of the acid and base parents. Use the guide below to determine the strength of a salt.

Helpful Links:
Cation vs Anion

Weekly Quiz

The quiz over this unit was not so bad. I feel like I knew the material, but just made a few simple mistakes. It was only 18 questions so missing a few really put a dent in my quiz grade, but it was not completely terrible. One of the things that really helped me was that none of the options for the math questions included "none of the above". This way I could see if the answer I got was actually right instesad of being unsure if I got the right answer and it purposely was not listed or if I completely messed up the problem. This quiz gave me a chance to correct any mistakes I made in my calculations if I did not come out with any of the numbers listed. This unit does not seem that bad yet, but I have heard so much about how hard it is, so I am waiting for it to hit me.

Unit Test

On Friday, we had our unit test for this unit. I feel like I did not completely fail it, but I do not think I did extremely well. I did many practice problems to review things such as molarity, solubility curves, and mass percent to prepare for the test, but I still had issues with some of the questions. I hope I did somewhat well because I do not want to start off the semester with a really bad grade in the class.

Murder Mystery Lab

   In this lab, we used our knowledge of molarity to determine who killed Miss Scarlet and with what. We were told that the substance that killed her was either silver nitrate or potassium iodide. We were also given a list of suspects that all had one of those two solutions in their possession, but with different molarities.We were also given sodium chloride and sodium carbonate to test with the unknown solution to determine its identity.

  Before we got into lab, we had to see which of the two options for the unknown substance (the substance used to kill Miss Scarlet) would react with which indicator, if any. For this we used our knowledge of double replacement reactions and solubility rules. The calculations for this step are shown below.

   When we tested the unknown substance with sodium chloride, the solution turned white, indicating a reaction. This meant that the unknown substance was silver nitrate. Then, we mixed 10 mL of silver nitatrate with 20 mL of .100M sodium chloride. The solution is pictured below.

   We then used filter paper (which we took the initial mass of) and filtered the solution into a separate beaker. We gave the filter paper a day to dry then took the final mass of it. We subtracted the initial mass from the final mass to find the mass of the precipitate. The calculations for this are shown below.

   We took this to find the molarity of the silver nitrate, which was .09M. This placed the murder substance in between the molarities of .05 and .15 which was listed in the suspect description of...

Helpful links that may help to understand this lab:

Solubility Rules

Double Replacement Reactions

How to Find Molarity

Weekly Quiz

We recently took our quiz over this current unit, aqueous solutions. The quiz was 24, so you could miss a couple of questions and still get a decent grade. The first two questions on the quiz were over limiting reagents which I forgot how to do. This freaked me out because I thought the rest of the quiz was going to involve them, but luckily, it did not. Today I got my quiz back and worked through those first two problems so I can do them if they appear on the test, which I assume they will. The rest of the quiz did not go horribly wrong. I did not get a fabulous grade, but I am fairly pleased with it. Hopefully I can do just as good if not better on the unit test Friday. 

Limiting Reagents Review

Limiting Reagent Review Video