1. Announcements Online HW #2 (Type 2) due tomorrow by 7:00 p.m.
Lab: bring usage card, wear appropriate attire, read Chapter 13
Lab write-up for lab this week is not due until next Wednesday, September 18th.

2. Clicker #1
You have two beakers on your lab table. Beaker #1 contains g of sulfur and Beaker #2 contains g of arsenic (As). Which beaker contains the greatest number of atoms? Choose the best answer.
A) Beaker #1 because one sulfur atom weighs less than one arsenic atom so you need more of the sulfur atoms to fill the beaker.
B) Beaker #1 because it contains more moles of sulfur atoms versus the number of moles of arsenic atoms in Beaker #2.
C) Beaker #2 because arsenic has a greater mass than sulfur.
D) Beaker #2 because it contains more moles of arsenic atoms versus the number of moles of sulfur atoms in Beaker #1.
E) Beakers #1 and #2 contain the same number of atoms because there is one mole in each.

3. Example
How many H2O molecules are contained in 50.0 g of water? How many hydrogen atoms are present in this sample?

4. Clicker #2
Does a methane molecule (CH4) consist of more hydrogen or carbon?
A) hydrogen
B) carbon
C) depends

5. Clicker #3
What is the percent composition (by mass) of carbon in 2 moles of CH4?
A) 2.00% C
B) 37.45% C
C) 74.9% C
D) 149.8% C

6. Example
You have some “nitrogen oxide” compound and you want to figure out what it is (both the formula and the name). You know it’s 30.4% nitrogen by mass.
NxOy = formula?
name?
See other document for more details on this problem!