I'm stuck with the following chemical equations
Zn(s)-->Zn2+(aq)+Zn-. Why is there a "2" there?
Cu2+ + 2e- --->Cu(s) Is this based on charges in the periodic table?
How would you find the net ionic equation of this as an example?
Ca(s)+ZnSO4(aq)--->CaSO4(aq)+Zn(s)
You don't use the periodic table to determine charges on transitional elements.They will always specify if the iron ion has a 2+ or 3+ charge. Copper, lead and tin generally have a 2+ charge when unstated. If they say copper has a 1+ charge, or lead/tin has a 4+ charge, then go with that.
The zinc ion has a 2+ charge
The silver ion has a 1+ charge
These are common ones that you need to just know. Just like how you need to know sulfates have a 2- charge.
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Analyse the species separately watching out for where an electron transfer has occurred:
Ca: It went from solid metal to becoming a calcium ion in calcium sulfate
Zn: It went from being an ion in zinc sulfate to just being a solid metal
SO
4: Nothing happened to sulfate
So you have Ca
(s) + Zn
2+ -> Ca
2+ + Zn
(s)