The trademark indicates the calcium carbonate content.

The mass of carbon dioxide produced by (1) is 2.5g×4+40.0g-47.8g=2.2g,

So fill in: 2.2.

(2) Let the mass of hydrogen chloride in hydrochloric acid be X and the mass of calcium carbonate in calcium tablets be Y,

CaCO3+2HCl═CaCl2+H2O+CO2↑，

10073? Forty-four

x y？ 2.2g

100x=73y=442.2g，

x=5g，y=3.65g，

The mass fraction of solute in the dilute hydrochloric acid used is: 3.65g 40.0g×100% = 9.1%,

Answer: The mass fraction of solute in dilute hydrochloric acid used is 9. 1%.

(3) The mass of calcium carbonate in each calcium tablet is 5g÷4= 1.25g,

Through calculation, it is known that the content of calcium carbonate per tablet is > 1.24 g, and the label of this calcium tablet is true.

(4) The mass fraction of calcium in this calcium tablet is:1.25G2.5g×100% = 50%,

A: The mass fraction of calcium in this calcium tablet is 50%.