metal hydroxide+SO2/CO2

Question

metal hydroxide+SO2/CO2
1.係咪任何metal hydroxide都同SO2/CO2有reaction?
定係Na,K,Ca only?

2.metal hydroxide+SO2/CO2一定出XXHCO3/XXHSO3先?
如果NaOH in excess
係咪同SO2 react 就出NaHSO3,再出NaSO3?

如果NaOH 未excess
係咪打錯

Answer 1

1)
Strong alkalis (e.g. NaOH, KOH and Ca(OH)2) react with CO2/SO2 very rapidly. Therefore, strong alkalis can be used to absorb CO2/SO2 effectively.
Many metal hydroxides (e.g. Fe(OH)3) are weak bases, which react with CO2/SO2 very slowly. Therefore, these metal hydroxides are not used to absorb CO2/SO2.

2).
CO2/SO2 and NaOH can react.
When CO2/SO2 is not in excess, the product is Na2CO3/Na2SO3.
2NaOH + CO2 → Na2CO3 + H2O
2NaOH + SO2 → Na2SO3 + H2O
When CO2/SO2 is in excess, the product is NaHCO3/NaHCO3.
Na2CO3 + H2O + CO2 → 2NaHCO3
Na2SO3 + H2O + SO2 → 2NaHSO3