ionic equations.... but how do i know the ion charges?

Question

okay... i understand the equation needs to be balanced.
i think.. .all the "aq" molecules split up into ions...
But HOW do i know that CuSO4 becomes:
Cu 2+(aq) + SO4 2-(aq)???

how do i find out?
many thanks x

they do give it to you without charges...
like:
CuCl2 (aq) + Mg(s) = Cu(s) + MgCl2(aq)

Answer 1

The best way is to know the monoatomic and polyatomic ions. All of the halogens (F, Cl, Br, I) that are written last in binary compounds have a -1 (neg 1) charge. The oxide ion is -2 etc. There should be a list of polyatomic ions in your chem book or from a list given to you by your teacher. Learn those and it usually easy to determine the charge on the cation (postive one) by the fact that the sum of all the charges in a molecule must be zero. EX. CaCl2 Note that there are 2 Cl ions each with negative 1 charge for a total of -2, calcium must be +2 to give a sum of zero.

Answer 2

You should have a list in your chemistry textbook of all the commonly occurring ions, or else your teacher should have given you such a list.

Incidentally, the 'aq' does not split up into ions, at least not to any extent that will affect the balancing of the equation. In neutral aqueous solution, only one molecule in 10,000,000 will be ionised. A solution of CuSO4, which will be weakly acidic, but even so, fewer than one molecule in 10,000 will be ionised.

As for the problem given: copper(II) chloride will be ionised into Cu++(aq) and Cl-(aq) and magnesium chloride will be ionised into Mg++(aq) and Cl-(aq). So writing it out in ionic form:
Cu++(aq) + 2 Cl-(aq) + Mg(s) ---->
Mg++(aq) + 2 Cl-(aq) + Cu(s)
Now we can cancel out the 2 Cl-(aq) from either side to give:
Cu++(aq) + Mg(s) ----> Mg++(aq) + Cu(s)

Answer 3

Copper metal under suitable conditions will readily ionise by losing its two outer electrons, to form Cu2+.Cation.
Sulphur and oxygen bond covalently in the sulphate anion. (SO4 2-). The sulphate anion is a very stable species.

Starting with Oxygen : for redox purposes it is given the value of -2.
As there are four oxygens then the oxygen part of the molecule has a value of 4 x -2 = -8.
As there is only one sulphur it will oxidise to its maximum : that is it will share/lose its six outer electrons and become S(VI). This means that in the overall state of the sulphate anion has +6 -8 = -2 hence the ionic charge on the anion. As mentioned the sulphate anion is a very stable species. so it will seek a cation(s) which have an overall charge of +2 (Cu2+), and copper readily ionises by losing its two outer electrons to form the Cu2+ cation.
Consequently the two ions are attracted together. to form CuSO4.

Answer 4

you dont, when balancing ionic equations they will give you the equation and all you have to do is balance it,
CuSO4 goes to Cu 2+(aq) + SO4 2-(aq)
if this is what was given to you then, i am a bit confused as to what you are supposed to be balancing as the atoms are balanced(1 Cu on left and 1 on right), (1 SO4 on left one on right)
but also the charges are balanced ( a 2+ and a 2- on the right makes it neatral, the same as on the left.) there is nothing to balance?!