[steph_r]

Hi there!
Just wondering whether i could have some assistance with this quesiton.

Calculate the number of ions present altogether in 25.0mL (0.025L) of 0.050M aluminium chloride (AlCl3)

I worked out the following:
The amount (in mol) of aluminium chloride: 1.3 x 10^ -3
The amount (in mol) of aluminium ions: (1.3 x 10^ -3) x 1 = 1.3 x 10^-3
The amount (in mol) of chloride ions: (1.3 x 10^ -3) x 3 = 3.9 x 10^ -3

I just don't know how to go about answering the question above.
Help would be greatly appreciated. Thanks 

[Astrokel]

hey steph_r

you are right and one more step to the answer and that is to covert to no. of ions for each species and sum them up

good luck

[steph_r]

Would i be able to have some assistance with that? That is, converting to no. of ions? I'll be able to add them up..

Im just a little bit confused..

Thank you for your help and patience, Astrokel

[Astrokel]

hey,

do you know about this formula?

No. of particles or ions = no of moles x Avogadro's constant

Avogadro's constant = 6.02 x 10^23

[steph_r]

Yes.. ive come across that formula, but ive always said: number of particles, instead of number of ions. I think thats why i got a little confused.. but not your fault 

So, do i use N = n/Na for both:
The amount (in mol) of aluminium ions: 1.3 x 10^-3, and
The amount (in mol) of chloride ions:  3.9 x 10^ -3

and then add them together? Is that what you mean?

Thank you once again

[Astrokel]

hey,

yes, but N=n/Na? sorry but i don't understand your notation for the formula. No of particles in general means ions, molecules, atoms...

[steph_r]

Sorry,
At school we use:
N = n / NA, meaning :

no. of particles = no. of mole / Avogadro's constant

[Astrokel]

hey

The formula is wrong, should be

hey,

do you know about this formula?

No. of particles or ions = no of moles x Avogadro's constant

Avogadro's constant = 6.02 x 10^23

[steph_r]

Thank you, Astrokel! I can't believe it was just a silly mistake..

Thank you for your help.. i really appreciate it!! 

[P]

At school we use:
N = n / NA, meaning :
no. of particles = no. of mole / Avogadro's constant

It is right if you take:

n = number of particles/molecules/ions
N = No. of moles
NA = Avagadro's number


I think you just mixed up the definitions of N and n.

[steph_r]

At school we use:
N = n / NA, meaning :
no. of particles = no. of mole / Avogadro's constant

It is right if you take:

n = number of particles/molecules/ions
N = No. of moles
NA = Avagadro's number


I think you just mixed up the definitions of N and n.

Yes, i think i did mix them up. At least now i won't forget.  Thank you!

[Mitch]

Remember Avogadro's number is easiest to remember in units of inverse mols (mol^-1) at this level of chemistry.

[calcium]

Remember Avogadro's number is easiest to remember in units of inverse mols (mol^-1) at this level of chemistry.

can u expand on that idea please

[Astrokel]

hey!

What Mitch is saying is that Avogadro's constant actually mean there are approximately 6.02 x 10^23 particles PER MOLE. Therefore the unit is in inverse mole.