tough chem question?

[dfgjgddjidfg]

how do i do it?

[stephanieteddy]

That one was so hard!

[stephanieteddy]

My teacher showed me this.

Q= It
   = 4200 C (This is the total Charge)

Now the charge on one electron = -1.6 * 10^-19   (From page 5 of the data booklet)

Sooo, the N(e-) = total charge / charge on one electron           

N(e-)=4200/(-1.6 * 10^-19) = 2.625 * 10^22              (Note capital N = number not mole)

We can see that n(Cu)=1.34/63.5 = 0.0211 mol, and since     2 mol of e- are required for 1mol of Cu to be formed, the amount of electrons reacting are  2* n(Cu) = 0.0422mol.

Avagadro's constant (NA) = Number of particles/number of mol  ---------> NA =N/n

So NA = ( 2.625 * 10^22)/0.0422 = 6.22 * 10^23

[dfgjgddjidfg]

thanks once again :p, i just had trouble finding the number of particles,so is that the formula  N(e-) = total charge / charge on one electron for finding the number of electrons         

[stephanieteddy]

Well yeh! It's like you have a bag that weighs 50g, and you know that each licorice bullet weighs 2 grams, the amount of licorice bullets = 25!

If you have a total charge of 50 and you know that each electron has a charge of 2, you know there are 25 electrons!

So it is total charge/ charge of one electron (-1.6*10^-19)