Question

Question #f33a3

Answer 1

There will be `4.33 xx10^(23)` atoms in the sample.

Explanation:

Whenever you must change the unit of measure in a Chemistry calculation, it is likely that the calculation will consider the number of moles at some point. This question is no exception.

First, we find moles of As, by dividing by the molar mass of the element (found on a periodic table)

moles As = `53.9 g-:74.9 g/"mol" = 0.720` mol

Next, to determine the number of atoms, we note that a mole of anything is equal to `6.02xx10^(23)` of those things.

`0.720 " mol" xx 6.02xx10^(23) "atoms"/"mol"=4.33xx10^(23)` atoms

Answer 2

`2.88*10^23` atoms

Explanation:

Arsenic :
Atomic number = 33
AMU = 74.92 (Atomic Mass Unit)
Avogadro's number = `6.022 * 10^23` (atoms per mol)
1 Mol As = 74.92 grams equals `6.022 * 10^23` atoms

Therefore, `1 gr. = (6.022 * 10^23)/ (74.92) " atoms"`
Or:`53.9/74.92 * (6.022*10^23) = 4.33*10^23 " atoms"` in your sample