Http://i64.tinypic.com/2gxmtyf.jpg - Question 19 why is answer (b)..?

A. False
Barium carbonate reacts with sulfuric acid to form insoluble barium sulfate which forms a solid layer coated on the surface of barium carbonate.
BaCO₃(s) + H₂SO₄(aq) → BaSO₄(s) + H₂O(l) + CO₂(g)
This insoluble solid layer separates the barium carbonate solid and the dilute sulfuric acid. As the two reactants are separated, the reaction stops in a short period of time after the reaction starts.

B. True
Barium carbonate reacts with dilute hydrochloric acid to form an aqueous solution of barium chloride.
BaCO₃(s) + 2HCl(aq) → BaCl₂(aq) + H₂O(l) + CO₂(g)
When dilute sulfuric acid is added to the barium chloride solution, a white precipitate of barium sulfate is formed.
BaCl₂(aq) + H₂SO₄(aq) → BaSO₄(s) + 2HCl(aq)
The barium sulfate precipitate is filtered off, washed with distilled water, and then dried in an oven. Barium sulfate solid is then obtained.

C. False
Sodium chloride does not react with barium carbonate solid. When dilute sulfuric acid is added, barium carbonate reacts with the sulfuric acid to form insoluble barium sulfate which forms a solid layer coated on the surface of barium carbonate.
BaCO₃(s) + H₂SO₄(aq) → BaSO₄(s) + H₂O(l) + CO₂(g)
This insoluble solid layer separates the barium carbonate solid and the dilute sulfuric acid. As the two reactants are separated, the reaction stops in a short period of time after the reaction starts.

D. False
Barium carbonate decomposes at 1360°C, and heating in laboratory is hardly to reach such a high temperature. Therefore, there is no reaction when barium carbonate is heated in laboratory. When dilute sulfuric acid is added, barium carbonate reacts with the sulfuric acid to form insoluble barium sulfate which forms a solid layer coated on the surface of barium carbonate.
BaCO₃(s) + H₂SO₄(aq) → BaSO₄(s) + H₂O(l) + CO₂(g)
This insoluble solid layer separates the barium carbonate solid and the dilute sulfuric acid. As the two reactants are separated, the reaction stops in a short period of time after the reaction starts.
However, suppose a high temperature heating is used to decompose barium carbonate to barium oxide.
BaCO₃(s) → BaO(s) + CO₂(g)
When sulfuric acid is added, the same problem occurs as a insoluble solid layer of barium sulfate is formed and coated on the surface of barium oxide.
BaO(s) + H₂SO₄(aq) → BaSO₄(s) + H₂O(l)
This insoluble solid layer separates the barium oxide solid and the dilute sulfuric acid. As the two reactants are separated, the reaction stops in a short period of time after the reaction starts.

...... The answer is : B. by adding dilute hydrochloric acid followed by dilute sulfuric acid