Question #2270c

1 Answer
Nathan L.
Aug 10, 2017

8.43xx10^24 "atoms C"

Explanation:

We're asked to find the number of atoms of "C" necessary to produce 12.0 "mol CO", given the reaction is

2"B"_2"O"_3(s) + 7"C"(s) rarr "B"_4"C"(s) + 6"CO"(g)

First, let's use the coefficients of the chemical equation to find the relative number of moles of "C" that react:

12.0cancel("mol CO")((7color(white)(l)"mol C")/(6cancel("mol CO"))) = color(red)(ul(14.0color(white)(l)"mol C"

Now, we'll use Avogadro's number (6.022xx10^23 "mol"^-1) to convert from moles to atoms:

color(red)(14.0)cancel(color(red)("mol C"))((6.022xx10^23color(white)(l)"atoms C")/(1cancel("mol C"))) = color(blue)(ulbar(|stackrel(" ")(" "8.43xx10^24color(white)(l)"atoms C"" ")|)

rounded to 3 significant figures, the amount allowed in the problem.

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