chem f.4 mole

Be careful to the question. It requires to find the no. of moles of the "ammonium ion" instead of ammonium carbonate.

No. of moles of (NH4)2CO3
= 9.6/(14*2+1*8+12+16*3)
= 9.6/96
= 0.1 mol
In ammonium carbonate, the mole ratio between NH4+ and CO3^2- = 2:1
No. of moles of ammonium ion
= 0.1 * 2
= 0.2 mol

2011-03-17 21:31:43 補充：
因此001的解答是有誤的

In order to calculate this type of questions
you must know the theory first
Once you have learnt the theory
you can diy (do it yourself) !

mass: ____ g
molar mass: ____ g mol-1
no of mole: _____ mol

Relationship:
mass / molar mass = (___ g) / (____ g mol-1)
g is cancelled then the ans's unit will be mol
therefore, we can simply know that
mass / molar mass = no.of mole of substance

From the above
mass of (NH4)2CO3 : 9.6g
molar mass of (NH4)2CO3 :[2x(14+1x4)+12+16x3]=96g mol-1

No of mole of (NH4)2CO3 : 9.6/96 = 0.1 mol

No of mole of NH4+ in 0.1 mol of (NH4)2CO3 : 0.1 x 2 =0.2mol


it is very easy!

number of moles of ammonium ion=MASS/molar mass
=9.6/(14+4+2x60)
=9.6/138
=0.069565217 mole

2011-03-17 20:53:34 補充：
睇錯
=9.6/(18x2+60)
=9.6/96
=0.1mole 先岩