Which ionic compound forms an acidic solution when dissolved in water?

Question

Which ionic compound forms an acidic solution when dissolved in water?

NH4Br

NaHCO3

KCl

NaN

Answer 1

When ionic compounds are dissolved in water, they break apart into their two ionic components and break down to some degree. Water consists of H⁺ ions and OH^- ions, so the two ionic components will bond with the two ionic components of water, which will create both an acid and a base in the solution. The degree at which the ionic components of the ionic compound dissolve depends on the strength of the acid and base formed in the water. Strong acids and strong bases will completely dissolve in water. All of the strong acids are: HCl - hydrochloric acid, HNO₃ - nitric acid, H2SO₄ - sulfuric acid, HBr - hydrobromic acid, HI - hydroiodic acid, HClO₄ - perchloric acid. All strong bases are: LiOH - lithium hydroxide, NaOH - sodium hydroxide, KOH - potassium hydroxide, Ca(OH)₂ - calcium hydroxide, Sr(OH)₂ - strontium hydroxide, and Ba(OH)₂ - barium hydroxide.

There are four different kinds of solutions made when compounds are put in water. They are: strong acid + strong base, strong acid + weak base, weak acid+ strong base, and weak acid + weak base. For a compound to form an acidic solution when dissolved, the compound must form a strong acid + weak base only, since strong acid + strong base and weak acid + weak base combinations will cancel out and make a neutral solution. A weak acid + strong base will make a basic solution.

You know what ions bond with what other ions in water because you want an ion with a ⁺ charge to bond with one with a ^- charge, and vice versa. H ions in water have a + charge and OH ions in water will have a - charge.

Starting with NH₄Br, it will break down into NH₄⁺ and Br^-, where H⁺ bonds with Br^- to form HBr, and NH₄⁺ bonds with OH- to form NH₄OH, which is a strong acid and weak base combo.

NaHCO₃ will make H₂CO₃ and NaOH, which is a weak acid strong base combo.

KCl will make HCl and KOH, which is a strong acid strong base combo.

NaN makes HN and NaOH, a weak acid strong base combo.

NH₄Br is the only compound that will make a strong acid weak base combo, and therefore, an acidic solution when dissolved in water.

Answer 2

Of these salts, Ammonium Bromide NH4Br is formed from ammonia (ammonia - NH3) a weak base and HBr a strong acid. So this is an acid salt.

On hydrolysis - NH4 + H20>>> H3O + NH3

The NH4+ ion donates a hydrogen to water forming H30 (a hydroniun ion) making NH4+ a weak acid and NH3 its conjugate weak base.

Rule of thumb: A salt formed from the combination of a strong acid and a weak base will form an acid salt and a salt formed from a strong base and a weak acid will form a basic salt.