Answer:
[tex]\boxed {\boxed {\sf B. \ 76.0 \ g }}[/tex]
Explanation:
We are asked to find the mass of 4 moles of fluorine atoms.
We will convert moles to grams using the molar mass. This is the mass of 1 mole of a substance. These values are found on the Periodic Table. They are equivalent to the atomic masses, but the units are grams per mole instead of atomic mass units.
Look up fluorine's molar mass.
We will convert using dimensional analysis so we must set up a ratio.
[tex]\frac {18.9984032 \ g \ F}{ 1 \ mol \ F}[/tex]
We are converting 4 moles of fluorine atoms to grams, so we multiply this value.
[tex]4 \ mol \ F *\frac {18.9984032 \ g \ F}{ 1 \ mol \ F}[/tex]
The units of moles of fluorine cancel.
[tex]4 *\frac {18.9984032 \ g \ F}{ 1}[/tex]
A fraction with a denominator of 1 is equal to the numerator, so we can ignore the denominator.
[tex]4 *18.9984032 \ g \ F[/tex]
[tex]75.9936128 \ g \ F[/tex]
Let's round to the tenths place. The 9 in the hundredth place tells us to round the 9 in the tenths place to a 0, then the 5 in the ones place rounds to a 6.
[tex]76.0 \ g \ F[/tex]
4 moles of fluorine atoms are equal to 76.0 grams of fluorine and choice B is correct.
