First we must find the molar weight of 1 mole of [tex] Mg_{3} N_{2} [/tex]. We take the atomic mass from the periodic table of each of the elements and that is the molar weight, in grams, for 1 mole of that element.
We know that in the chemical formula of [tex] Mg_{3} N_{2} [/tex], we have 3 moles of Mg and 2 moles of N. So we need to multiply these numbers in order to get the correct amount for the compound:
Mg: [tex] 24.305g*3=72.915g [/tex]
N: [tex] 14.007g*2=28.014g [/tex]
So then we add these two together to get the total molar weight of the compound, [tex] Mg_{3} N_{2} [/tex]:
[tex] 72.915+28.014=100.929g [/tex]
So now we know that the molar weight of [tex] Mg_{3} N_{2} [/tex] is [tex] \frac{100.929g}{mole} [/tex]
We want to know how many grams are in 4.5 moles, so we must multiply and cancel out the units:
[tex] \frac{100.929g}{1 mole}*4.5mol=454.18g [/tex]
Now we know that there are 454.18 grams of [tex] Mg_{3} N_{2} [/tex] in 4.5 moles of [tex] Mg_{3} N_{2} [/tex].
