Stoichiometry: Mole-Mole?

My high-school chemistry class is working on stoichiometry...I have problems with moles. I think I get Mole-Mass and maybe Volume-Volume, but I do not get Mole-Mole...if someone would please help me out! Here is an example, a question from my homework:

*sub= subscript

NH(sub)2 + 3H(sub)2 -->2NH(sub)3

How many moles of hydrogen are needed to completely react with two moles of nitrogen?

I do not get how to set up the equation...walking me through this, giving me a formula, even a useful link. Or, if anybody can recommend some good chemistry books to assist me! I really do appreciate your help!

In this reaction, gaseous hydrogen (H2) and NH2 are reacting to form ammonium (NH3).

For every one mole of NH2, you need 3 moles of gaseous hydrogen (H2). So, if you had twice as much NH2, you'd need twice as much hydrogen.

Hope that helps.

first u should balance the reaction equation,

2NH2 + H2 -->2NH3

the coefficients in front of the formulas are usd to figure out the mole ratio between them. so, 2 moles of NH2 will react with 1 mole of H2. i.e. the mole ratio betweem NH2 and H2 IS 2:1

HOPE THIS HELPS:-)

I'm sort of doubtful that the educt is NH2 - there is no such (stable) molecule).

Possible alternatives:

N2

N2H4

HN3

Anyway, about your basic problem: don't think moles when writing the equation, but count the atoms on both sides of the arrow. If the same number of atoms of each element is found on both sides of the arrow, the equation is potentially correct.

BTW, the subscripts are usually ignored when writing molecules in ASCII. In case of several sub- and super-scripts, use (lots of) brackets.

So:

N2 + 3 H2 -> 2 NH3

This equation is already balanced.

N2H4 + H2 -> 2 NH3

HN3 + 4 H2 -> 3 NH3