How many moles of nitrogen, #N_2#, are there in #4.3*10^23# #N_2# molecules?
In order to figure out how many moles of nitrogen gas would contain that many molecules, you need to know how many molecules of a substance are needed in order to make one mole.
If you know how many molecules of a substance you get in one mole, you can use this as a conversion factor to help you find the answer.
The number of molecules that are needed in order to have one mole of a substance is known as Avogadro's number and is equal to
#color(blue)(|bar(ul(color(white)(a/a)"1 mole" = 6.022 * 10^(23)"molecules"color(white)(a/a)|))) ->#Avogadro's number
This is true regardless of the substance you're dealing with. Simply put, in order to have a mole of anything, you need to have
Use Avogadro's number as a conversion factor to get
#4.3 * 10^(23)color(red)(cancel(color(black)("molec. N"_2))) * overbrace("1 mole N"_2/(6.022 * 10^(23)color(red)(cancel(color(black)("molec. N"_2)))))^(color(purple)("Avogadro's number")) = "0.71405 moles N"_2#
Rounded to two sig figs, the number of sig figs you have for the number of molecules of nitrogen, the answer will be
#"no. of moles N"_2 = color(green)(|bar(ul(color(white)(a/a)0.71color(white)(a/a)|)))#