Tuesday, May 10

Today was a very productive class period. In the beginning of the class period, we stayed in the classroom, reviewed Kevin and Kendall's blog, and got our quizzes back.

To do the last problem on the quiz, you had to write the equation consisting of the conjugate base of the weak acid. This would make the equation...

H20 + NO2- ---> HNO2 + OH-

You would then have to set up an ICE table where NO2- would have an initial amount of 2.50 molarity. This is because the problem stated that there were 2.50 M of sodium nitrite (NaNO2). Since NO2- is acting as a base, and we got the Ka value, we have to figure out what the Kb value would be. To do this, one would have to do Kw over Ka which is..

1.00 x 10^-14

7.0 x 10^-4

The Kb value would turn out to be 1.49 x 10^-11. From there it is all algebra (minus the 5% dissociation theory) and the same type of problem we have been doing all unit to find out what the pH value would be.

We spent the remainder of class doing a titration lab. Since it was our first time, our results were not super great as our indicator turned a dark pink instead of an ideal light pink. The procedure of the lab went as the follow. One would have to rinse the buret multiple times to ensure that it was clean. Then, one lab partner would get 30 mL of NaOH solution in a 100 mL beaker and rinse the buret with the NaOH solution. Then, another person would mass out between .30 and 1.00 grams of KHP and would put it in a 250 mL Erlenmeyer flask.

The most important part of the lab comes next...adding three drops of phenolphthalein. If one misses this step, they would have to start all over. After that, one records the initial reading of the buret. Next, the titration of the NaOH solution begins until a light pink color lingers for more than 30 seconds. Now someone records the final reading of the buret.

This is only one titration trial and will have to be repeated at least 2 or 3 more times. It was a very busy day in Mr. Henderson's class. The homework was to finish the labs 1,2, and 3 which we have been working on.