I) The equation for the reaction taking place in Flask A is:

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4)

i) The equation for the reaction taking place in Flask A is:

$$\text{ZnCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{ZnCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$$

ii) The product(s) are passed through water to remove acidic impurities (like hydrogen chloride gas or acid spray) from the carbon dioxide gas.

iii) One disadvantage of passing products through water is that some of the carbon dioxide gas will dissolve in the water, leading to a loss of the desired product.