Question #9001f

1 Answer
Jul 4, 2017

Answer:

There are #7.64 × 10^20 color(white)(l)"atoms Au"#.

Explanation:

Step 1. Calculate the mass of pure gold

If the mass of the ring is 300 mg, then

#"Mass of Au" = "300 mg" × (20 color(red)(cancel(color(black)("kt"))))/(24 color(red)(cancel(color(black)("kt")))) = "250 mg"#

Step 2. Calculate the moles of #"Au"#

#"Moles of Au" = 0.250 color(red)(cancel(color(black)("g Au"))) × "1 mol Au"/(179 color(red)(cancel(color(black)("g Au")))) = "0.001 269 mol Au"#

Step 3. Calculate the atoms of #"Au"#

#"Atoms of Au" = "0.001 269" color(red)(cancel(color(black)("mol Au"))) × (6.022 × 10^23color(white)(l) "atoms Au")/(1 color(red)(cancel(color(black)("mol Au"))))#

#= 7.64 × 10^20 color(white)(l)"atoms Au"#