Answer:
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
