When you did the 9 Bottles experiment in General Chemistry 1, explain why you di

Question

When you did the 9 Bottles experiment in General Chemistry 1, explain why you did not observe a precipitate when you mixed equal volumes of 0.01 M BaCl_2 is mixed with 0.1 M Pb (NO_3)_2 The Ksp for PbCl_2 is 2 4 times 10^-4. Barbiturate acid, HC_4 H_3 N_2 O_3, a monoprotic acid, is used to prepare various barbiturate drugs. Calculate the concentration of hydrogen ion and pH in 100.0 ml of 0.250 M solution of the acid. The value of K_a is 9.8 times 10^-5. If 25.0 ml of 0.50 M NaOH is added to the above solution, what is the pH of the resulting solution? After a total of 50.0 ml of 0.50 M NaOH is added, what is the pH of this solution now? What is the pH of the resulting solution after 55 0 ml of 0.50 M NaOH? What is solubility? What is the solubility product? How will intermolecular forces (IMF) affect the solubility of KHTar? How will the effect of IMF be verified in next week's experiment?

Explanation / Answer

Q1.

why no precipitate when mixing:

BaCl2 + Pb(NO3)2

Note that for precipitate to form

We require Q > Ksp

meaning

[Pb+2]actual * [Cl-]^2actual > [Pb+2]equilibrium * [Cl-]^2equilibrium

calcualte actual values

[Pb+2] = M1*V1/(V1+V2) = 0.1*V1/(V1+V1) = 0.1/2 = 0.05

[Cl-] = M2*v2/(V1+V2) = 0.01*V1/(V1+V1) = 0.005 M

Q = 0.05*0.005 = 0.00025

Q = 2.5*10^-4

since Q is approx the same value of Ksp, then this is in EQUILIBRIUM

in order to expect large amount of precipitates, Q >> Ksp

this is why the amount of precipitate is not visible, since it is too low, i.e. equilbrium is achieved

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