計ｍｏｌｅ　＆　ｅｍｐｒｉｒｉｃａｌ　ｆｏｒｍｕｌａ

The basic unit of nitrogen is N atom.

Only nitrogen gas exists as N2 molecules. Two N atoms combine to form one N2 molecules.

Nitrogen-containing compound are formed by combining N atom(s) with other atom(s). For example, NH3 molecule contains 1 N atom and 3 N atoms.

In the compound between R and N (The basic units in compounds are atoms) :
No. of moles of N = 28/14 = 2
Since 3 moles of R combine with 2 moles of N, thus the empirical formula is R3N2.

2008-06-26 01:32:22 補充：
其實任何物質都是由 atoms 所造成的，2 粒 N atoms 造成一個 N2 molecules，N atoms 亦造成其他物質。

所以計算 empirical formula 都是用 atoms 計。記住，兩粒 O atoms 造成 O2，兩粒 N atoms 造成 N2。O2 和 N2 是產物，唔會用來造其他物質。

造任何物質，都係用 atoms。就算 CO2，都係 1 粒 C atom 加 2 粒 O atoms 造成。你諗下，NO (nitrogen monoxide) 點解會存在呢？

我諗你係計no of moles of nitrogen 果陣出左事

因為nitrogen 係diatomic, 所以formula 係N2, 唔係N

No. of mol of N2:
28/(14*2)
=1mol

所以empirical formula 係R3(N2)1 =R3N2