Question

Question #2270c

Answer 1

`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.