The main component of eggshells is calcium carbonate. In order to determine the content of CaCO 3 in eggshells, an interest group took 12.5 g of eggshells, put them in a beaker, and then

① The amount of carbon dioxide is:

4.4g

44g/mol

= 0.1mol;

So the answer is: 0.1

②Set the amount of calcium carbonate in egg shells to x. Then

CaCO 3 +2HCl=CaCl 2 +H 2 O+CO 2 ↑

1? 1

x 0.1mol

0.1mol

Solve for x=0.1mol?

Mass fraction of CaCO 3 = (0.1mol x

100g/mol

12.5g

) x 100% = 80%?

Answer: the mass fraction of CaCO3 in this eggshell is 80%.

③ Let the amount of dilute hydrochloric acid required in the reaction be y,

CaCO 3 +2HCl=CaCl 2 +H 2 O+CO 2 ↑

?2?1

y 0.1mol

then

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0.1mol

Solve for y=0.2mol;

The amount of HCl before the reaction=

80g×18.25%

36.5g/mol

=0.4mol,

So the amount of HCl remaining is: 0.4mol-0.2mol=0.2mol;

So the answer is: 0.2mol.