1st lesson

Today in class, we had our first lesson on our new unit: Acids and Bases. We first learned about the physical properties of acids and bases:

http://chemwiki.ucdavis.edu/Textbook_Maps/General_Chemistry_Textbook_Maps/Map%3A_Chemistry%3A_The_Central_
Science_(Brown_et_al.)/04._Reactions_in_Aqueous_Solution/4.3%3A_Acid-Base_Reactions

In addition to the picture above, acids feel sticky to the touch, like syrup.

Next, we discussed Arrhenius acids and bases. Arrhenius acids are acids that produce hydrogen ions in a solution. Arrhenius bases are bases that produce hydroxide ions in a solution. So, when put in a solution, the compound that they are a part of breaks apart and either increases the hydrogen or hydroxide concentration in the solution, depending on what is dissolved.

According to the pH scale, the lower the pH, the higher the hydrogen ion concentration in the solution. On the other hand, the higher the pH, the higher the hydroxide ion concentration.

We also learned about Bronsted- Lowery acids and bases. According to this definition, acids donate a proton and bases accept a proton. In B.L. definitions, we also have conjugate acids and bases. Acids produce conjugate bases and bases produce conjugate acids. You can see this in the picture below:



Here are a couple links to practice the new concepts we learned:
acid base quiz
acid and base quiz

Vitamin C Lab Day 1

     Today in class, my lab partner and I did part of the vitamin c lab. First, while waiting for the vitamin c lab standard solution to be made by another lab group, we filled up our different pipets with apple juice, pear juice, V8 juice, white grape juice, starch, and iodine. We made sure to keep the iodine dark and covered in tin foil to prevent it from decomposing. While performing the lab, on one round, we took 20 drops of the vitamin c standard solution and added three drops of starch to that. Then, we added drops of iodine, making sure to count all the drops, until the solution changed from clear to a dark blue. The dark blue color indicated the end of the reaction between the vitamin c and the iodine. We repeated this a few more times, switching out the vitamin c solution with the different juices. Here are some pictures from the lab:

Here is also a helpful website about our new unit:
Acid Base Link

Exam Prep

While studying ahead for the exam today, I picked out which questions from all the practice tests on schoology and the book that were most helpful to review:

Chapter 15 solutions quiz-
questions 29, 30, 22

Chapter 15 standardized test practice-
questions 7, 13, 14, 15

Chapter 15 solutions big test-
questions 10, 14, 16, 17, 40, 47, 48, 49, 51-55, 61, 63

Book Questions-
standardized test practice questions 1, 11
chapter 15 assessment questions 3, 11, 20, 27c, 35-38, 42, 43, 52-54

Hope you find this helpful!

Molarities with Stoichiometric Calculations

Last week, we learned how to use molarity with stoichiometry. Below are some steps to help guide you through problems:

Mrs. Frankenberg also showed us this chart to help you know what to do next in this type of stoichiometry questions:

A question we practiced with involved an aqueous solution of sodium sulfate and lead nitrate,  forming a solid lead sulfate precipitate. It wanted to know the mass of lead sulfate formed when 1.25 liters of 0.0500 M lead nitrate and 2.00 liters of 0.0250 M sodium sulfate are mixed.

To find the mass, we first had to use the molarity formula of moles of solute/ total volume of solution to find the amount of moles in each of the reactants. We then converted the moles of each on two separate equations to grams of lead sulfate formed using a mole to mole ratio. Whichever reactant produced a smaller amount of lead sulfate was the mass of lead sulfate, since it was the limiting reagent.

Here are a couple links with practice problems:

Stoichiometry using molarity ws

Solution stoichiometry

Murder Investigation Lab

On Monday and today, my lab partner and I performed the Murder Investigation Lab. On Monday, we were given the clues to the murder with several suspects, each including their names and the molarities and the amounts of their possible murder weapons. We discovered that the weapon was most likely silver nitrate after solving a few chemical reactions on paper with the chemicals we would be given to test with on Wednesday.

Today, we performed the lab, only testing to silver nitrate with one of the solutions we were given, sodium carbonate, to check our prediction. Like we guessed, the silver nitrate and sodium carbonate did make crystals when they were mixed. We filtered the crystals and set them out to dry for us to weigh tomorrow. Once we know the mass of the crystals, we can convert it to moles and divide it by the total amount of solution it was mixed in to discover its concentration. Then we will compare the concentrations to the suspects' murder weapons to solve the mystery.

Below are some pictures from the lab:

Sodium Carbonate and Silver Nitrate mixed

Flask with funnel, filter, and solution

Leftover crystals in filter paper

Dilution Notes

On Friday, we learned about dilutions. You know if a problem on a test or quiz involves a dilution if the question starts and ends with the same solution. In a dilution, you regularly start with a a stock dilution and add water. With serial dilutions, you make subsequent solutions from an original stock by continuing to dilute it down. The amount of solution you move and add more water to each step is the aliquot.

http://www.quansysbio.com/dilutions

To solve problems involving a dilution, you use the following equation:

http://study.com/academy/lesson/calculating-dilution-of-solutions.html

Something to remember is that the V2 in the equation represents the total solution, which is the aliquot + the water used.

Here is a link to a couple websites where you can learn more about dilutions and use the dilution formula with practice problems:

ChemTeam: dilutions

Dilution Worksheet

Mass Percentage, Molarity, and Concentrations of Ions

Today in chemistry class, we learned about mass percentage, morality, and concentrations of ions in solutions. First, we discussed mass percentage. Below is the equation of how to solve it:

http://cbse-notes.blogspot.com/2012/07/cbse-class-9-ch2-is-matter-around-us.html

A very important thing to remember is that the mass of the solution is not just the solvent, but the solute and the solvent combined. By knowing two parts of this equation, one is able to find the third when solving for the missing variable.

Next, we learned about Molarity. To find Molarity, you have to divide the moles of a solute by the Liters of solution.

http://www.wikihow.com/Calculate-Molarity

Something to remember is that volume can change with temperature, so morality can also change with temperature. You can also manipulate this equation to find the different components within it if you have at least two of the variables. For example,

(Volume(L)) x mol/1L = mol

Lastly, we talked about concentrations of ions. With this, we use the Van't Hoff factor. This factor only applies to ionic compounds. To find the number of ions released in a compound, you must break the compound down. For example, sodium carbonate has a Van't Hoff factor of 3 since Na2CO3 -> 2Na+  +  CO3 2-. With this information, you can find the total ion concentration. 

Here are a couple websites to practice problems that relate to this lesson:

ChemTeam

Molarity

Concentrations of Ions