How many atoms are there in each of the following?

Question

a. 1.50 mol Na
b. 6.755 mol Pb
c. 7.02 g Si

PLEASE SHOW WORK!!!

Answer 1

Some hints:

There are 6.023 x 10 to the 23rd atoms in every mol of any element. (doesn't matter whether it's Na or Pb.)
Also there are 6.023 x 10 to the 23rd molecules in every mol of any compound (like NaCl or H20 for instance).

Soooo to get the answers for a. and b., all you need to do is to multiply the amount of mols you have for each substance times 6.023 x 10 to the 23rd. Also 6.023 x 10 to the 23rd is known as Avogadro's Number.

Knowing what I just told you about the number of particles in every mol will help you find the answer to c, but you need a little more information.

Here's a link to the periodic table:
http://images.google.com/imgres?imgurl=http://www.corrosionsource.com/handbook/periodic/periodic_table.gif&imgrefurl=http://www.corrosionsource.com/handbook/periodic/&h=480&w=580&sz=19&tbnid=G4wY8RtD2Q3CMM:&tbnh=111&tbnw=134&prev=/images%3Fq%3Dperiodic%2Btable&start=1&sa=X&oi=images&ct=image&cd=1
Click on the link, then click on Si
Look at the table and find the atomic weight (should be 28.086)

Now for example, if you have 28.086 grams of Si, then you have a mol of Si.
(That works for all the other elements as well, you just have to look up the unique atomic number for each.)

Now you have to ask yourself, "What fraction of a mol of Si do I have if I have 7.02g?"

Answer: 7.02/28.086 mol

Now convert the number of mols to atoms the same way you did for a. and b. by multiplying times Avogadro's Number.

Hope that helps.