Here are the answers to the worksheet I gave you in class.  Again, they look a little different because of my HTML abilities, but you should be able to tell what is going on.  If you are having trouble with these, come see me - ASAP!  Remember, the test is on Friday.

1.  What is the mass in grams of 3.6 mol of the element carbon, C?

            3.6 mol C   x    12.01 g C     =     43. g C                    (the 12.01g came from the periodic table)
                                     1 mol C

2.  What is the mass in grams of 0.733 mol of the element chlorine, Cl?

            0.733 mol Cl     x     35.45 g Cl     =     25.98 g Cl --->    26.0 g Cl  (adjusted for sig fig's)
                                            1 mole Cl

3.  How many moles of copper, Cu, are in 3.22 g of copper?

            3.22 g Cu     x        1 mol Cu      =   0.0506 mol Cu
                                        63.55 g Cu

4.  How many moles of lithium, Li, are in 2.72 x 10^-4 g of lithium?

            2.72 x 10^-4 g Li     x     1 mol Li      =    3.94 x 10^-5 mol Li        (don't let the ugly numbers fool you - they gave you
                                               6.91 g Li                                                grams and asked for moles -- so just go with it!)

5.  How many moles of C are in 2.25 x 10²² atoms of C?

            2.25 x 10²² atoms C    x              1 mole C          =    0.037 mol C
                                                    6.022 x 10²³ atoms

6.  How many moles of oxygen, O₂ , are in 2,000,000 atoms of oxygen?

            2,000,000 atoms O₂      x           1 mol O₂                 =      3.  x  10^-18 mol O₂ 
                                                       6.022 x 10²³ atoms

7.  How many atoms of sodium, Na, are in 3.80 mol of sodium?

            3.80 mol Na     x      6.022 x 10²³ atoms    =   2.29 x 10²⁴ atoms Na
                                                    1 mol

8.  What is the mass in grams of 5.0 x 10⁹ atoms of neon, Ne?

            5.0 x 10⁹ atoms Ne    x             1 mol Ne                    x    20.18 g Ne   =   1.7 x 10^-13 g Ne
                                                      6.022 x 10²³ atoms                 1 mol Ne

        (This one had three steps.  Why??  Because you are only allowed to make two types of conversion factors - we couldn't change atoms directly into grams -- we can only change them into  moles.  THEN we can change the moles into grams.)

9.  How many atoms of C are in 0.020 g of C?

                0.020 g C    x      1 mol C      x    6.022 x 10²³ atoms    =   1.0 x 10²¹ atoms C
                                          12.01 g C                1 mol C
 
10.  What mass of silver, Ag, contains the same number of atoms as 10.0 g of boron, B?
        (This is a hard one -- it is an extra credit type of problem.)

        First, I found out how many moles were in 10.0 g of B --

                        10.0 g B     x       1 mol B       =  0.925 mol B
                                                 10.81 g B

        Then, I remembered that according to Avogadro - one mole of ANY substance always contains   6.022 x 10²³ atoms.  So
            if I can figure out the mass of 0.925 mol of silver, then I have my answer....

                           0.925 mol Ag     x     107.87 g Ag     =    99.8 g Ag
                                                            1 mol Ag