Hi I have read conflicting things on this and more than just a little confused:

firstly what will be the end products also why? These are the things I have read which seem to be conflicting:

 

That NaCl will dissolve due to the lone pairs of electron on the oxygen and the partial positive charge from the protons.

 

But I have also read that adding NaCl will have no effect.

 

I'm especially interested in the effect of adding NaCl to speed up/slow down rate of reaction.

 

Thank you!

NaCl will dissolve because it is very soluble in water. This has nothing to do with the reaction between HCl and Mg, however, and I see no way that it would act as a catalyst.