#24.08 times 10^23# atoms of boron is equal to how many moles of Boron?
Here's what I got.
For starters, notice that your sample contains
#24.08 * 10^(23) = 4 * (color(blue)(6.02 * 10^(23)))#
atoms of boron. At this point, you should be able to recognize the fact that
In other words, a mole of boron is defined as
This means that your sample contains
#4 * color(blue)("1 mole B") = color(darkgreen)(ul(color(black)("4.000 moles B")))#
You must report the answer rounded to four sig figs, the number of sig figs you have for the number of atoms present in your sample.
SIDE NOTE As an interesting fact, Avogadro's constant is often times approximated to
#24.08 * 10^(23) color(red)(cancel(color(black)("atoms B"))) * "1 mole B"/(6.022 * 10^(23)color(red)(cancel(color(black)("atoms B")))) = "3.99867 moles B"#
Rounded to four sig figs, the answer would be
#"no. of moles = 3.999 moles B"#
So make sure that you use the value for Avogadro's constant provided to you by your textbook.