Which of the listed salts will orthophosphoric acid interact with? K2SO4, SnCl2, Zn (NO3) 2, Na2SiO3

Answer: with Na2SiO3.
Explanation: there is a rule that says that when an acid interacts with a salt, the salt must be soluble in water, the acid must be stronger than that in the salt, and a precipitate, gas or water must precipitate as a result of the reaction.
This rule is satisfied only by the variant of interaction of orthophosphoric acid with sodium silicate (orthophosphoric acid is stronger than silicic acid, as a result a precipitate of silicic acid will precipitate, Na2SiO3 is soluble):
2H3PO4 + 3Na2SiO3 = 2Na3PO4 + 3H2SiO3.

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