(1) According to the label, the volume of the bottle of concentrated sulfuric acid is 500mL, the density is 1.84g/cm3, and the mass of the bottle of concentrated sulfuric acid solution before opening is 500ml× 1.84g/cm3 = 920g.

(2) The mass of dilute sulfuric acid =19.6%10g× 98%19.6% = 50g.

So the answer is: (1) 920; (2)50.