Which pair of substances would most likely result in the production of a solid when reacting with a base? litmus and phenolphthalein soluble metal salt and carbon dioxide acids and water hydrogen ions and soaps

Soluble metal salt and carbon dioxide

Both soluble metal salt and carbon dioxide may react with a base to form a solid or what we call a precipitate.

Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)

Ca(NO₃)₂(aq) + NaOH (aq)→ Ca(OH)₂(s) + NaNO₃(aq)

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explanation:

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.