Will a precipitate form if you mixed 30.0 mL. of 0.011 M AgNO_3 with 50.0 mL of

Question

Will a precipitate form if you mixed 30.0 mL. of 0.011 M AgNO_3 with 50.0 mL of 0.080M Na_2SO_4? the K_sp for Ag_2SO_4 is 1.5 times 10^-5. NO CREDIT GIVEN YOU DON'T SHOW YOUR WORK CLEARLY. In a solution of 0.85 M KOCI, which ion will a affect the pH? Write the chemical equilibrium for the reaction of this ion with water. Include physical states. is the equilibrium constant for the reaction K_a or K_b? Set up an ICE table and calculate the pH of this solution 0.85 M KOCI. SHOW YOUR WORK! remember there are constants on the front page. What is the concentration of HOCI in this solution?

Explanation / Answer

20. Qsp for Ag2SO4 = [Ag+]^2[SO4^2-]

                                 = (0.011 M x 30 ml/80 ml)(0.08 M x 50 ml/80 ml)

                                 = 2.06 x 10^-4

As Qsp > Ksp, precipitate would form : Yes

21. a) KOCl the ion affecting pH is OCl-

b) OCl- + H2O <==> HOCl +H-

c) The equilibrium constant is Kb

d) ICE table

                    OCl- + H2O <==> HOCl + OH-

initial           0.85                          -           -

change         -x                            +x        +x

Eq             0.85-x                         x           x

So,

Kb = 1 x 10^-14/3.5 x 10^-8 = x^2/0.85-x

x^2 + 2.86 x 10^-7x - 2.43 x 10^-7 = 0

x = [OH-] = 4.93 x 10^-4 M

pOH = -log[OH-] = 3.31

pH = 14 - pOH = 10.65

e) concentration of [HOCl] = 4.93 x 10^-4 M

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