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

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 $\left( g/mol \right)$.