Which compound produces a basic solution when dissolved in water?

Question

A. Ca(NO3)2; B. NH4Cl; C. KClO4; D. KCl; E. NaF

How do you judge this and why? Thanks...

Answer 1

im pretty sure C and D are both out because they are both acids

a) calcium nitrate

b)ammonium chloride

e) sodium floride

im going to have to say B ammonium chloride beacuase ammonium is a base? correct me if im wrong its either b or ebut im pretty sure its b

Answer 2

NH4Cl, ammonium chloride, is acutally mildly acidic when dissolved in water.

When determining the pH of a salt, you need to look at the strength of the *conjugate acid* and *conjugate base* formed from each ion. From your choices, I would say that sodium fluoride (NaF, choice 'E') is the answer since it is the salt formed from HF, a weak acid, and sodium hydroxide, a strong base...

Answer 3

E.  NaF will form a basic solution . F-1 is the conjugate base of the weak acid HF which has an ionization constant of ~ 10^-4.

This means that F-1 is a moderately strong base and will compete with OH-1 for protons ( that is, F^-1 will have a tendency to strip a proton from water) making a solution that contains a small amount of OH-1..which will be basic . The weaker the acid the stronger is its base and the pH will become more and more basic for those conjugate bases of weaker and weaker acids

      F^-1 + H2O  ------   HF + OH-1 ----  increases pH

Kh = Kw/Ka=   ~ 10^-10

NO3-1, nor ClO4^-1  cannot hydrolyze as they are the conjugate bases of the very strong nitric and perchloric acids. That means their bases have NO tendency to gain a proton.  NH4+ is the conjugate acid of the base ammonia and will hydrolyze to produce an acid solution, not basic