Chemistry 2A Week 5 Review

    This week in chemistry was not too eventful. We spent much of the week reviewing for the Unit 5 Test on Friday, which I'm pretty sure I did a-mole-zing on.

     On Monday we took a short quiz that tested us on conversion skills. We had to go from grams to moles, moles to grams, and moles to atoms. I got 8/8 on the quiz and I understood it. I just messed up on significant figures. I don't understand sig figs at all, I just focused on doing the work right.
Unit 5 Quiz 1c

 

     On Tuesday we completed Unit 5 worksheet 3. We learned the difference between empirical and molecular formulas. Empirical are experimental based while molecular is exact and based on the actual number of atoms in each compound. When given the molar mass, you find the empirical formula and adjust according to what the molar mass is. Like in problem 4 of worksheet 3. We find the empirical formula to be HO. However, we have a molecular mass of 34 g/mol. So you take the atomic mass of Oxygen, 16, and since there is only one Oxygen in the empirical formula, you add 16 to the atomic mass of one Hydrogen, which is 1. If the empirical would have been H2O2 the we would have done 16x2 + 2x1 because of the number of atoms in the empirical formula.

     Anyways, we take 34, our molar mass, and divide it by 17 (H+O). This equals two. So now the molecular formula is H2O2 because the molar mass divided by the atomic mass sum is two. I understood this after some practice with worksheet 3. Explaining and discussing with my table mates helped me get a better understanding of this.

Unit 5 worksheet 3



 

 

     On Wednesday we had PSAT testing and didn't do anything in class.

 

     We spent all of Thursday doing the unit 5 review. There were some things I didn't remember, like relative mass, but now I remember after doing the review. For relative mass, you just divide all your data by the smallest number you got. The data is relative to the smaller number.

     The review also included more conversions, and more problems with empirical and molecular formulas. I felt prepared for Friday's test.

Problems from review guide

 

     On Friday we took the Unit 5 test. I thought it went pretty well. There were probably some stupid mistakes I made but I knew what the questions were asking. I still have no idea about sig figs. I didn't pay attention to them on the test.

 

     Overall I thought it was a good week. We reviewed a lot which really helped. I look forward to seeing what I got on my test!!

 

 

P.S.-What is Avogadro's favorite holiday??

 

 

Cinco de Mole-o!!