Question #ccabc

1 Answer
Jun 21, 2016

Answer:

#4.63*10^-20# gram

Explanation:

You can get to the answer in two steps:

  1. calculate: 500 atoms = #color(red)x# mol ?
    using Avogadro's constant.
  2. calculate: #color(red)x# mol = #color(red)?# grams,
    using the atomic mass of Iron.

Step 1
Avogadro's constant says that #1# mole of any atom contains #6.022*10^23# atoms. In this case you have #500# atoms:

#(500 color(red)cancel(color(black)("atoms")))/ (6.022*10^23 color(red)cancel(color(black)("atoms"))/"mol"# = #8.30*10^-22 mol#

Step 2
The atomic mass of iron (Fe) will give you the weight of one mole of this molecule: #1# mol = #55.845# gram:

#55.845 g/(color(red)cancel color(black)"mol") * 8.30*10^-22 color(red)cancel color(black)"mol"# = #4.63*10^-20 g#

So the 500 iron atoms weigh #color(red)(4.63*10^-20) color(red)"grams"#.