Problems: Decide which of the following salts will form acidic, basic, or neutra

Question

Problems: Decide which of the following salts will form acidic, basic, or neutral solutions when dissolved in water. (Hint: look at the acids and bases that formed them) 1. For example: KCH COO was formed in the reaction between KOH and CH,COOH. KOH is a strong base. Its conjugate acid, K", has negligible acidity and will leave the pH at 7.00, a neutral solution. CH COOH is a weak acid, making its conjugate base, CH3COO a relatively strong weak base. It will produce a basic solution. Analyze the following salts in the same way: a) KF b) NaNO3 c) NH4NO3 d) KCN e) Rbl f) Na CO Rank the salts (from #1) from most acidic to least acidic. You may need a Ka or Kb table for this last exercise. Assume all solutions are 1.0 M 2.

Explanation / Answer

1.

a)KF. It is formed from Strong base KOH and weak acid HF. so the aquesous solution of KF is Basic.

b) NaNO3. It is formed from Strong Base NaOH and strong acid HNO3. so the aqueous solution of NaNO3 is neutral

c)NH4NO3. It is formed from weak base NH4OH and strong acid HNO3. so the aqueous solution of NH4NO3 is acidic

d) KCN . It is a salt from strong base KOH and weak acid HCN. so aqueous solution is basic.

e)RbI. It is a salt of strong base RbOH and strong acid HI. so the solution is neutral

f)Na2CO3. It is a salt of strong base NaOH and weak acid H2CO3. so the solution is basic.

2.for strong substances Ka and kb values are greater than 1.

KF

ka of HF =7.2 x10^-4

NH4NO3

kb for NH4OH = 1.8 x 10^-5

KCN

ka for HCN = 6.2 x10^-10

Na2CO3

Ka for H2CO3=2.1 x10^-4

by using these values

Na2CO3 > KF >NH4NO3 > KCN.

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