4.7 describe experiments to prepare soluble salts from acids

You need to pick an insoluble base, and the acid of the salt you want to make (sorry that was a bit confusing, I couldn't really find another way to word it). Basically, if you was to make copper nitrate, mix nitric acid and copper carbonate (remember all carbonates are insoluble except sodium, potassium and ammonium carbonate)...

CuCO_3(s) + 2HNO_3(aq) ---> Cu(NO₃)_2(aq) + CO_2(g) +  H₂O_(l)


All you need to do is add the metal oxide, carbonate or hydroxide (aka the insoluble base) to the acid. The base will react with the acid and dissolve.  

NOTE: This is a neutralisation reaction, you will know when the reaction is over as this is when all the acid has been neutralised (this is when the excess solid will sink to the bottom of the flask and not react anymore)

Next, filter the solution to get rid of the undissolved base and evaporate the water to leave pure salt crystals.