# How many grams are there in 4.50 moles of Ba(NO_2)_2?

number of moles (n) = 4.50 moles
mass (m) = $n \times M$ [This is what you are trying to find]
molar mass (M) = ?

Your first step is to find out what is the molar mass (M) of $B a {\left(N {O}_{2}\right)}_{2}$.

To find a molar mass of a compound, break the compound up into component parts so you could see what elements are involved.

If you break $B a {\left(N {O}_{2}\right)}_{2}$ up, you can clearly see that it is composed of Ba, N and O.

You got to find the molar mass of each elements involved. You can identify the molar mass straight away if you look into the periodic table.

Ba = $137.3 g m o {l}^{-} 1$
N = $14.0 \times 2$ because there is a number 2 after the closing bracket so $28.0 g m o {l}^{-} 1$
O = There are 2 O atoms inside the bracket and doubled because of the 2 outside the closing bracket, so there are 4 O atoms altogether. $16.0 g m o {l}^{-} 1 \times 4 = 64.0 g m o {l}^{-} 1$

So to get the molar mass of $B a {\left(N {O}_{2}\right)}_{2}$, add the molar mass of the elements up. $137.3 + 28.0 + 64.0$ and that will give you $229.3 g m o {l}^{-} 1$. Therefore the molar mass of $B a {\left(N {O}_{2}\right)}_{2}$ is $229.3 g m o {l}^{-} 1$.

n = 4.50 moles
m = ?
M = 229.3 $g m o {l}^{-} 1$

Step 2, you can now find the mass of $B a {\left(N {O}_{2}\right)}_{2}$. To find the mass, you need to multiply the number of moles (n) with molar mass (M), in other words, $m = n \times M$

$m = 4.50 \times 229.3 = 1031.85$

Therefore, there are 1031.85 grams in 4.50 moles of $B a {\left(N {O}_{2}\right)}_{2}$.