Question

What mass (in g) of nitrogen are needed to react completely with 5.8 g of hydrogen?

Answer 1

We have the following chemical reaction:

`N_2+3H_2\rightarrow2NH_3`

First we calculate the moles of hydrogen that react. For this we use its molar mass:

`M_(H_2)=2.1(g)/(mol)=2(g)/(mol)`
`n_(H_2)=(5.8g)/(2(g)/(mol))=2.9mol`

Now, we know that for every 3 moles of H2 we need 1 mol of N2, so we calculate the moles of N2:

`n_(N_2)=2.9mol_(H2)(1mol_(N2))/(3mol_(H2))=0.97mol`

And now we use the nitrogen's molar mass to calculate the grams:

`M_(N_2)=2.14(g)/(mol)=28(g)/(mol)`
`m_(N2)=0.97mol.28(g)/(mol)=27g`

So the answer is 27g