What must be produced for a double-replacement reaction to occur?

What must be produced for a double-replacement reaction to occur?





a. Solid precipitate


b. Gas


c. Molecular compound


d. All of the above

What must be produced for a double-replacement reaction to occur?
I think that if (d) is intended as a possible answer it should be "any of the above". You don't need them all at once.





Think about these reactions and decide if they count as double displacements:





You make sodium chloride and silver nitrate solution, and make solid silver chloride





You pour concentrated sulphuric acid onto sodium chloride, and I left with solid sodium hydrogen sulphate and HCl gas (do not try this at home)





You react an organic acid and an alcohol, and end up with an ester and water.





Over to you.