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

The correct answer is soluble metal salt and carbon dioxide.

Explanation:

Both the carbon dioxide and the soluble metal salt may react with a base to produce a solid or what is known as a precipitate. An example of soluble metal salt like calcium nitrate when reacts with a base like sodium hydroxide, leads to the generation of solid calcium hydroxide and sodium nitrate, the reaction is known as the precipitation reaction.  

Ca(NO₂)₂ (aq) + NaOH (aq) ⇒ Ca(OH)₂ (s) + NaNO₃ (aq)

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation:

the correct answer would be b. amelia, because the particals of gas move really fast (charged particals) and gas also has a lot of room (particals move independently) so the only answer that has both of those is amelia's.