Indicate whether each of the following compounds will give an acidic, basic or neutral solution when dissolved in water. Clear All ammonium bromide potassium hypochlorite calcium perchlorate ammonium nitrate The pH will be less than 7. The pH will be approximately equal to 7. The pH will be greater than 7. Submit AnswerRetry Entire Group

1.-  pH < 7

2.- pH > 7

3.- pH approximately 7

4.-  pH < 7

Explanation:

To answer this question we should think in terms of finding in each salt the acid  and base from which it came from, and determining  for the  the cation and/or anion, the possible hydrolization hydrolization reactions.

1.-ammonium bromide, NH₄Br, salt forms from the neutralization reaction:

NH₃           +     HBr  ⇒               NH₄⁺                   +                   Br ⁻

weak base   strong Acid    weak conjugate                very weak conjugate

                                            acid of weak base NH₃    base of strong acid HBr

                                             Ka = 5.6 x 10⁻¹⁰

Thus the pH will be determined by NH₄⁺ and the pH < 7

2.-potassium hypochlorite, KClO :

KOH          +   HClO      ⇒         ClO⁻                       +                H₂O +       K⁺

Strong base   weak acid       conjugate base of                     neutral    neutral

                                               of weak acid HClO

Here the pH will be driven by the conjugate base ClO⁻ since water is neutral. Therefore pH > 7

3.- calcium perchlorate, Ca(ClO₄)₂:

Ca(OH)₂      +   HClO₄     ⇒       ClO₄⁻                     +                    H₂O +    Ca²⁺

strong base    strong acid        very weak conjugate                neutral  neutral

                                                  base

Here the conjugate base coming from the strong acid HClO₄ will be a very weak one for all practical purposes. The pH will be approximately 7 since it will not hydrolize to any appreciable extent.

4.- ammonium nitrate , NH₄NO₃ :

HNO₃          +      NH₃         ⇒     NH₄⁺                          +            NO₃⁻      

very strong      weak base        weak conjugate              very weak conjugate

acid                                             acid                                  base

                                                   Ka = 5.6 x 10⁻¹⁰

Here the pH will be dominated by the conjugate acid NH₄⁺ since NO₃⁻ is a very weak base. Thus its pH will be less than 7