5.7, 5.8 Acid-Base and Gas-Evolution Reactions

5.7 Acid-Base Reactions 5.8 Gas-Evolution Reactions

acid-base reaction aka neutralization reaction

a reaction in which an acid reacts with a base and the two neutralize each other, producing water (or in some cases a weak electrolyte)

gas-evolution reaction

a reaction in which two aqueous solutions are mixed and a gas forms resulting in bubbling

true

(true/false) Acid-base reactions and gas-evolution reactions occur when the anion from one reactant combines with the cation of the other.

false

(true/false) Gas-evolution reactions and acid-base reactions are mutually exclusive.

Arrhenius definition of acid

substance that produces H+ ions in aqueous solution

Arrhenius definition of base

substance that produces OH- ions in aqueous solution

hydronium ion

H₃O⁺ formed when bare protons H⁺ associate with water molecules

true

(true/false) The proton H+ is always solvated.

hydronium

Chemical equations for the ionization of acids is often written to show the association of a proton with a water molecule to form the ___________ ion: e.g. HCl(aq) + H₂O(l) → H₃O⁺(aq) + Cl^-(aq)

polyprotic acid

acid which contains more than 1 ionizable proton and release them sequentially

strong, weak

The first ionizable proton is ______ (strong/weak) while the subsequent ionizable protons are usually ______ (strong/weak).

diprotic acid

an acid that contains two ionizable protons

2

In an analogy to diprotic acids, some bases produce __ moles of OH^- per mole of the base.

acid + base → water + salt

generic equation for acid-base reactions

H⁺(aq) + OH^-(aq) → H₂O(l)

net ionic equation for acid-base reactions involving strong acid

titration

a laboratory procedure in which a substance in a solution of known concentration (titrant) is reacted with another substance in a solution of unknown concentration (analyte) in order to determine the unknown concentration

equivalence point

the point in the titration at which the added solute completely reacts with the solute present in the solution; for acid-base titrations, the point in the titration when the number of moles of base is stoichiometrically equal to the number of moles of acid

• n(H+) = n(OH-)

false

(true/false) The equivalence point always occurs at a pH of 7.

indicator

a dye whose color depends on the pH of the solution in which it is dissolved; often used to detect the endpoint of a titration

intermediate product

Some gas-evolution reactions form gaseous product directly when the cation of one reactant combines with the anion of another. Other gas evolution reactions often form an ________________________ that then decomposes into simpler substances to form a gas.