How high must a metal be in the reactivity series for it to react with an acid to given hydrogen gas?

Chemical formula for

Sodium carbonate + sulphuric acid → sodium sulphate + water + carbon dioxide:

For the first part see Reactivity series - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Reactivity_series)

For the second part, it's very simple so I'm not going to give it away, if you want to have a stab at it, then I can see where I can help you.

It's Ok, I Got It Worked Out Anyway...