[trisperon]

I'm posting this question based on a chemistry book's solution which tells that given the molar mass of the substances:

[tex]\frac{85 g}{30g} = \frac{1000g}{x}[/tex]
where:

[tex]x=0.35kg[/tex]
What I don't understand is that if urea contains 2 moles of N compared to Sodium Nitrate, then why do we have to divide the entire molecule's mass by 2 if only the N atoms are questioned?

[Borek]

If you have 10 molecules of sodium nitrate you have the same number of atoms as in 5 molecules of urea, don't you? So to have the same amount of nitrogen you need twice less urea molecules, hence division by two.