Gastric juice, the digestive fluid produced in the stomach, contains hydrochloric acid, and HCl. Milk of Magnesia, a suspension of solid Mg(OH)₂ in an aqueous medium, is sometimes used to neutralize excess stomach acid. Write a complete balanced equation for the neutralization reaction, and identify the conjugate acid-base pairs

Conjugate acid-base pairs are acid-base pairs that differ only by one proton. The loss or gain of a proton leads to the formation of such acid-base couples.

Milk of magnesia is Mg(OH)₂and it is used to neutralize gastric acid HCl for balanced neutralized reaction.

\[2HCl(aq) + Mg{(OH)_2}(aq) \to MgCl{l_2}(aq) + 2{H_2}O(l)\]

To determine acid or conjugated base and base or conjugated pairs in the ionic form

\[2HCl(aq) + Mg{(OH)_2}(aq) \to M{g^{2 + }}(aq) + 2{C^ - }(aq) + 2{H_2}O(l)\]

Bronsted-Lowry’s acid is a proton donor, while it is a base is proton acceptor.HCl after donating proton become as Cl^-. Mg (OH)₂accepts proton from HCl to produce a molecule of water and Mg²⁺, so that Mg (OH)₂is a base .To determine if the product is an acid or a base it is called conjugate to from reactants Cl^-to accept the proton in order to become HCl as a conjugated base. Mg²⁺is a conjugated acid.

The conjugate acid-base pairs are

\[2HCl(aq) + Mg{(OH)_2}(aq) \to MgC{l_2}(aq) + 2{H_2}O(l)\]

Acid:HCl

Base: Mg (OH)₂

Conjugated acid: Cl^-

Conjugated base: Mg²⁺