I got this in a past exam and how exactly are you mean to work out the answer?

 

 

And if charges moving in a circuit aren't negative then what are they? (I somehow doubt they are talking about positrons here)

 

(I've got the answer here, but I don't know how to reach it.)

The key would be to look at possible charge carriers in each of the substances.

 

Molten NaCl comprises of Na+ and Cl- ions.

 

Potassium Nitrate, KNO3, exists as K+ and NO3- ions in solution.

 

Acidified water contains excess H+ ions.

 

Aluminium has a large number of mobile electrons available to carry charge.

But an ion in solution (or liquid) will conduct electricity, so wouldn't the other 3 options also conduct electricity?

 

But yes, the answer was

Yes they will conduct electricity, but the current would also be due to +ve charges and the questions ask which one will be due only to negative carriers.

Oh, so (I think), in A, B & D electrolysis would occur, whereas in C (molten Al) only electrons would flow, there wouldn't actually be electrolysis.

 

but the current would also be due to +ve charges

But current is electrons, what +ve charges? Or do you just mean positively charged ions?

I am referring to the ions yes.

 

What occurs at the cathode when a positive ion approaches?

What occurs at the cathode when a positive ion approaches?

Was that rhetorical? Yeah I know though, electron is attracted to it... the +ve ion is attracting the electron which causes the electron to move which causes a current.

 

Oh, so (I think), in A, B & D electrolysis would occur, whereas in C (molten Al) only electrons would flow, there wouldn't actually be electrolysis.

Is that correct?

I've added you to my msn - it'll be easier to explain that way!

Basically to finish off for anyone interested...

 

Post #7 is correct!