Thursday, May 12, 2011

Today, class started off with Mr. H giving out a handout that dealt with titration curves. The worksheet was simply a review of what we had learned last Friday in class, but Mr. H felt we needed a review because weren’t quite able to fully understand the concept of titration.

On the first side of the sheet, we learned the concept of titration when a strong acid is mixed with a strong base. Similar to the lab we did the previous day, Mr. H talked to us about the procedure of adding base to an acid with a few drops of phenoplathian. What happens is as base is added to the aqueous solution it slowly reacts away with the H+ inside of the beaker. As soon as there is more OH-, then H+ in the beaker the solution would turn pink. At that point is when titration was reached. This gave a better explanation of what exactly happens when a solution is being titrated.

On the second side of the sheet, we learned about titration when a weak acid is mixed with a strong base. This was also similar to the lab. OH- is constantly added to the beaker as well, but the only difference in this case is that that point of titration is reached earlier. This is because less of the H+ dissolves inside of the phenoplathian. The solution turned to pink faster than when the strong acid and strong base were mixed with each other. Learning these two concepts gave an insight into how to complete the previous labs, and to understand the new lab, Ab7, we were going to do. Lab AB7 required us to find the molarity or concentration of an unknown substance.

During the lab, we had to perform the titration procedures using multiple trials. Almost the whole class finished with time left, so we went to the front of the classroom to discuss the results we got. The point of the lab was to use the basic formula of MaVa=MbVb. The concentration for the base was carried over from the averaged concentrations found in the previous lab. With that, we were able to find the concentration for the unknown substance.

Class ended at that point, and Mr. H reminded us of the 32 point WebAssign we had that was due tomorrow. We only have to get 22 points to get a 100 on the assignment.