Calculate the p H in 0.25 M solution of N H 4 F . (Hint: The principal reaction

Question

Calculate the pH in 0.25 M solution of NH 4 F . (Hint: The principal reaction is proton transfer from the cation to the anion.) See Appendix C in the textbook for values of equilibrium constants. Express your answer using three significant figures. pH = Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M Calculate the pH in 0.25 M solution of NH 4 F . (Hint: The principal reaction is proton transfer from the cation to the anion.) See Appendix C in the textbook for values of equilibrium constants. Express your answer using three significant figures. pH = Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M pH = Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M pH = Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M pH = Calculate the concentration of NH 4 + , F ? , NH 3 , HF , OH ? and H 3 O + in 0.25 M solution of NH 4 F . Express your answers using two significant figures separated by commas. [NH 4 + ],[F ? ],[NH 3 ],[HF],[OH ? ],[H 3 O + ] = M

Explanation / Answer

NH4F -----> NH4+ + F-

NH4+ -----> NH3 + H+ and F- + H2O----> HF + OH-

Ka = 7*10^-4

so, Kb = 1.43 * 10^-11

1.43 * 10^-11 = [HF][OH-]/[F-]

1.43 * 10^-11 = x^2/0.25-x

since Kb<<1, ignore the x

.43 * 10^-11 = x^2

x = [OH-] = 3.78*10^-6 M

so, [H+] = 2.64 * 10^-11M

we have NH4+ ---> NH3 + H+

Ka NH4+ = 5.56*10^-10 = [NH3][H+]/ [NH4+]

5.56*10^-10 = x^2

x = [H+] = 2.36*10^-5 M

therefore pH = 4.6

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