Question

He table below lists some acids and bases. Strong acids Weak acids Weak bases Strong bases HBr CH3COOH NH3 NaOH HNO3 HCOOH NH4OH KOH H2SO4 Ca(OH)2 Which salt has a pH < 7?
A) KBr
B) HCOOK
C) CaSO4
D) NH4NO3

Answer 1

The answer is D)NH4NO3

Answer 2

Answer : Option D) $NH_{4}NO_{3}$

Explanation :

Amongst the given list of acids and bases, following are the strong acids and weak acids

Strong Acid: HBr, $HNO_{3}$ and $H_{2}SO_{4}$

Weak Acid: $CH_{3}COOH$ and HCOOH

And strong bases with weak bases are given below;

Strong Base: NaOH, KOH and $Ca(OH)_{2}$

Weak Base: $NH_{4}OH$ and $NH_{3}$

Now, Acid  + Base    →    Salt   + Water

so, the salt of strong acid and weak base which will have pH < 7

will be $NH_{4}NO_{3}$

because of the following acid base reaction (neutralization reaction)

$HNO_{3}$     +      $NH_{4}OH$   ↔    $NH_{4}NO_{3}$    +    $H_{2}O$