Tuesday, February 12, 2013
Reporters write and publish news stories for their local station or newspaper. They often report from the site of the news and interview people associated with the story. These interviews are compiled with pertinent facts and reported via radio, tv, or in a newspaper. A bachelor's degree is journalism, as well as a love for writing is necessary to succeed in this position. The average yearly salary is $36,000. The industry and position is growing atan average rate. Form ore information, you can contact local newspaper writers (Sun Times) for perspective on the job or field.
Wednesday, March 23, 2011
T(b)=i x m x k(b)
You are supposed to solve for molality here. The ionic solid has 2 ions so i would equal 2. m would equal the molality and k(b) is a constant, which would be 0.51 for water. The T(b) is the Delta H that comes from the data in the lab. The homework is to finish up the post lab which is due on friday. Also there are 3 WebAssigns due on friday so keep up with them. The next scribe is Lauren C.
Tuesday, March 22, 2011
1.Vapor Pressure Lowering
2. Boiling Point Elevation
3. Melting Point Depression
4. Osmotic Pressure
Basically, the relations are simple. The more solute added, the more the vapor pressure decreases. The more solute added, the more the boiling point raises. The more solute added, the lower the melting point becomes. We also got a few formulas to accompany the above.
To calculate the change in boiling point(Blogger isn't letting me use equation editor, get notes off moodle to really see this):
Change in Boiling Point=molal boiling point elevation constant x molality
Traingle T subscript b= K subscript b * m
To calculate freezing point depression, you use the same formula except the constant is different. The K subscript b is repaced with K subscript f.
The van't Hoff factor basically mens that if you have a mole of NaCl, and the ions dissociate when in water, you will get one mole of Na+ ions and one mole of Cl- ions. The van't Hoff factor is i so simply modify the previous equations by multiply i to the end like so:
Triangle T subscript f= K subscript f * m * i
That pretty much sums it up for new material covered today. Liebs demonstrated these new concepts with one demo involving 4 of us as water molecules, showing that the more solute added (balloons), the more interactions we had to make with it (touching each ion), which made it harder for us water molecules to turn into our gaseous state. Also, we took some club soda, stuck it into some ice and upon opening the glass, thus releasing the CO2 which had raised the freezing point, the club soda immediately froze.
Liebs also discussed some issues with the faulty Webassign that was due today, and said he would make corrections. I know it probably frustated myself as much as did to some of you (honestly, comment if you remembered how to use sig figs before this unit started).
That's about all though. Homework tonight is to do all the worksheets you have been given this unit that are due on the day of the test, as well as the 3 remaining webassigns also due on the day of the test.
Justin J., come on down, you are the next contestant on the price is right.
Monday, March 21, 2011
Sunday, March 20, 2011
Hey Guys! So today in chem class we went over notes on molarity and molality dilution.
The first concept that we talked about was the concentration of solute. That is, the amount of solute in a solution is given by its concentration. There are four units if concentration.
The first is molartiy and you can compute it by this equation, molarity (M) = moles of solute/liters of solution. This equation comes in hand when you are trying to figure out the mass of a substance needed to make a certain amount of solution at a specific molarity, or to simply find the molarity of a solution.
The second unit in with you can compute the concentration of a solution is molality, be sure to not get this and molarity confused for the sound very similar. With this unit the equation is molality (m) of solution moles of solute/kilograms of solvent.
The third unit in with you can compute the concentration of a solution is percent by mass. The equation of this unit is % by mass = (grams of solute/grams of solution) X 100.
The fourth and final way of compute the concentration of a solution is by finding the mole fraction. To find this you use the equation mole fraction (x) = moles of solute/ moles of solvent + moles of solution. For this you want to remember to have your final answer be in decimals.
The second concept we discussed was molarity and dilution. This concept talked about diluting a solution and this is simply adding more solvent, in our case water, to the solution. This will dilute the solution but remember that the amount of solute does not change and because of this, it is really easy to calculate the new molarity. All you do is take the information you have (at least three points) and plug it into the equation, MaVa=MbVb.
That was all for today’s class. Homework for Monday is to finish your lab and do the webassigns also remember to keep up with your work sheets.
The next scribe is …………………….. Rachel M.
Thursday, March 17, 2011
Today in 7th Period Chem we did yet another lab! This one dealt with measuring the saturation temperatures for six difference solution concentrates to construct a solubility curve.