Steve Marsden’s

What should happen to the conductivity of the mixture?

What if the salt produced is insoluble?

Acids can also react with metal oxides but the visual evidence generally looks like simple dissolving. The chemical process that occurs, however, is very much like the reaction of an acid with a base. In fact, a metal oxide can be thought of as a "base without water".

acid + metal oxide ® salt + water
H2SO4 + MgO
® MgSO4 + H2O

We also saw that acids react with metal cabonates to release carbon dioxide gas. A metal carbonate is just a metal oxide which has picked up carbon dioxide, and so:

acid + metal carbonate ® salt + water + carbon dioxide
2 HCl + K2CO3
® 2 KCl + H2O + CO2