[Shadow]

What processes happen at magnesium and zinc plates if they are immersed in hydrochloric acid and not touching each other.

Probably both metals get oxidized:
Mg+2H⁺ Mg²⁺+H₂
Zn+2H⁺ Zn²⁺+H₂

What happens if they are connected by a wire?

Now, I think that magnesium is protecting zinc and that these processes happen:
Mg Mg²⁺+2e^- at magnesium plate,
2H⁺+2e^- H₂ at zinc plate.

Is my reasoning correct?

Also I was though that salts are called, for example sodium-chloride with the line between sodium and chloride. Now, in many references I see that the small line isn't written, sodium chloride. Is this a new rule or both names are acceptable?
 

[Hunter2]

I am not sure magnesium is strong enough to protect zinc.

The - is not used , for what reason should it be.
English language seperates , other languages dont. So  Natriumchlorid you can find some where else.

[Shadow]

Why not  -it has a much lower electrode potential.

[confusedstud]

What processes happen at magnesium and zinc plates if they are immersed in hydrochloric acid and not touching each other.

Probably both metals get oxidized:
Mg+2H⁺ Mg²⁺+H₂
Zn+2H⁺ Zn²⁺+H₂

What happens if they are connected by a wire?

Now, I think that magnesium is protecting zinc and that these processes happen:
Mg Mg²⁺+2e^- at magnesium plate,
2H⁺+2e^- H₂ at zinc plate.

Is my reasoning correct?

Also I was though that salts are called, for example sodium-chloride with the line between sodium and chloride. Now, in many references I see that the small line isn't written, sodium chloride. Is this a new rule or both names are acceptable?

Your reasoning seems correct to me. Like an electrolytic cell.

[ramboacid]

The reasoning seems correct in that Zn would draw electrons from Mg, however wouldn't the Mg also react with the acid at the same time?

[confusedstud]

The reasoning seems correct in that Zn would draw electrons from Mg, however wouldn't the Mg also react with the acid at the same time?

I don't think so, in a electrolytic cell the less reactive electrode doesn't get eaten away. I think that's the basic fundamentals for sacrificial protection, I'm not too sure about how much protection one piece of more reactive metal can give though.

[CKabes]

The reduction potential of Magnesium is more negative than Zinc, making it more likely to be oxidized by the acid. Magnesium is also used as a "sacrificial anode" on the hulls of ships and such, so it may "protect" the zinc...to a certain extent.

[jepdiniz]

Wouldn't the Mg react with the HCl ?
Mg + 2HCl --> MgCl2 + H2

[confusedstud]

Wouldn't the Mg react with the HCl ?
Mg + 2HCl --> MgCl2 + H2

magnesium is more reactive than zinc, its an electrolytic cell question.

[Shadow]

All in all, I concluded from your responds that mine reasoning is correct. Thanks to everyone for taking part in this.