Question

If you start with \[5.5\] grams of sodium fluoride how many grams of magnesium fluoride will it produce in the reaction?
\[Mg+2NaF\to Mg{{F}_{2}}+2Na?\]

Answer 1

Hint: To solve this question we know about the molar mass of a compound is the mass of a given chemical element or chemical compound (g) divided by the amount of substance. It can be calculated by adding the standard atomic mass \[\left( g/mol \right)\] of the constituent atoms.

Complete step by step answer:
Mass of sodium fluoride \[=5.5g\]
\[\left( NaF \right)\]
\[moles=\dfrac{mass}{molar\,mass\,of\,NaF}\]
\[Moles=\dfrac{5.5g}{\left( 22.99+18.998 \right)g/mole}\]
\[moles=\dfrac{5.5}{41.998}moles\]
\[moles=0.13096\]moles of \[NaF\]
for every \[2\]moles of \[NaF\] there is \[1\]mole of \[Mg{{F}_{2}}\]
\[\dfrac{0.13096\,moles\,of\,NaF}{2}=\dfrac{moles\,of}{Mg{{F}_{2}}}\]
Moles of \[Mg{{F}_{2}}=0.06548moles\]
Now, to convert this into grams
\[moles=\dfrac{mass}{molar\,mass\,of\,Mg{{F}_{2}}}\]
\[0.06548\,Moles=\dfrac{mass}{\left( 24.305+2\left( 18.998 \right)g/mol \right)}\]
\[0.6548=\dfrac{mass}{62.301g}\]
Mass of \[Mg{{F}_{2}}=4.1\,grams\]

It will be \[4.1g\] of \[Mg{{F}_{2}}\] produced.

Note: Molar mass of an element is simply the atomic mass in \[g/mol\], However, molar mass can also be calculated by multiplying the atomic mass in amu by the molar mass constant \[\left( g/mol \right)\].