Question

2. Consider the following solutions at 25°C. Identify the major species present in each solution, and classify each solution as acidic, basic or neutral. Solution Major species Acidic/Basic/Neutral? 1.0.10M CH.NHBr (aq) 11. 0.10M KHCO3(aq) Explain your reasoning for your classification for Solution II. 3. Calculate the molarity of a Na HPO solution that would yield a pH of 10.59 at 25°C MacBook Air

Answer 1

2-

i- CH3NH3Br is a salt of weak base CH3NH2 and Strong acid HBr as-

HBr + CH3NH2 --------> CH3NH3Br

So in aqueous solution, CH3NH3Br dissociates as-

CH3NH3Br --------> HBr + CH3NH2

Again since HBr is a strong acid, it completely dissocilates in water as

HBr + H2O --------> H3O+ + Br-

And since CH3NH2 is a weak base, it partially dissocilates in water as

CH3NH2 + H2O --------> CH3NH3+ + OH-

And both the CH3NH2 and CH3NH3+ will coexist

So the majaor species found in the aqueous solution are-  CH3NH2 , CH3NH3+ and Br-

Now the nature of the solution will be as per the strong species i.e Acidic (due to HBr)

ii- Similarly

KHCO3 is a salt of weak acid H2CO3 and Strong base KOH as-

KOH + H2CO3 --------> KHCO3

So in aqueous solution, KHCO3 dissociates as-

KHCO3 --------> H2CO3 + KOH

Again since KOH is a strong base, it completely dissocilates in water as

KOH + H2O --------> K+ + OH-

And since H2CO3 is a weak acid, it partially dissocilates in water as

H2CO3 + H2O --------> H3O+ + HCO3-

And both the H2CO3 and HCO3- will coexist

So the majaor species found in the aqueous solution are-  H2CO3​​​​​​​ , HCO3- and K+

Now the nature of the solution will be as per the strong species i.e Basic (due to KOH)