Please answer my question

Solution:
b)
(i) Na₂S₂O₃ + HCl $\underset{}{\to }$ S + SO₂ + 2NaCl + H₂O
(ii) Ca(HCO₃)₂ + 2HCl $\underset{}{\to }$ CaCl₂ + 2CO₂ + 2H₂O
c)
i. 


ii. Such an arrangement is necessary to prevent back suction of water into the apparatus.
    Secondly, it provides a larger surface area for the dissolution of HCl gas.

iii.Below 200$°$C
NaCl + H₂SO₄  NaHSO₄ + HCl
Above 200$°$C
2NaCl + H₂SO₄  Na₂SO₄ + 2HCl
​​​