The Student Room Group

AS Chem

One mole of BeCl2 reacts with NaCl to form a new ionic compound which contains 23.3% by mass Na and 4.6% by mass beryllium.

1. Calculate empirical formula of this new compound- for this i have got BeNa2Cl - i didnt think i could have all three elements in one ionic compound, but since the %'s of Na and Be by themselves didnt add up, I added Cl too.... is this right ???

2. The Molecular formula of the compound is same as EF. Predict the shape of the berryllium-containing ion which exists in this compound ... - what is the berrllium containing ion ??!! If i knew that and it has only 2 elements in it i can work out the shape, if it has more than 2 elements... well im stuffed!

Can anyone help ?! please !
Reply 1
okkkk, does anyone know if you are able to predict the shape of a molecule containing 3 elements at AS or whether I'm meant to be choosing 2 of the elements out of BeNa2Cl to make an ion ???
Reply 2
Urm..sounds like a very wierd question...maybe it's just theoretical.
I got the compound to be:

BeNa2CL4

Using the ratios Be=0.5, Na=1 and Cl=2.

And assuming the Be atom is in the middle..i would predict an Octahedral shape...as thier are 6 other atoms (4 Cl's and 2 Na's)

That's my best shot...not too confident though...!
Reply 3
yeah i checked my empirical again - I got BeNa2Cl4 the second time (got my Cl fraction upside down)...
If it is an ionic compound and i have to give the structure of an ION dont I have to work out what the ion containing berillium is and then work out what charge that has, this is so confusing!
OR do I just do the shape of all 5 atoms without a charge, aaah !
Reply 4
hmm

did u do 100-(23.3.+4.6) = 72.1% of Cl?
#
using that i get Na2BeCl4
Reply 5
lol sorry, yes that is what i meant, i'll edit my post
any ideas about the shape or the ion ?
Reply 6
this is just ionic, the 2 Na atoms transfer their 1 outershell electron to one Cl atom each, and the Be tranfers each of its 2 outershell electron to 2 Cl atoms..


..?