1.) What is the pH of a buffer that consists of 0.43 M CH 3 NH 2 and 0.90 M CH 3

Question

1.) What is the pH of a buffer that consists of 0.43 M CH3NH2 and 0.90 M CH3NH3Cl? (pKb of methylamine (CH3NH2) = 3.35.)

(a) 0 mL

(b) 10.00 mL

(c) 15.00 mL

(d) 20.00 mL

(e) 25.00 mL

Qsp ?

Ksp ?

5.) In a qualitative analysis procedure, a chemist adds HCl to an unknown group of ions and then saturates the solution with H2S so that the solution is 0.4 M in HCl and 0.10 M in H2S.

   a) What is the [HS -] of the solution? (Note: The answer should be rounded to one significant figure. Be careful, 3.5 rounds up to 4, but 4.5 rounds down to 4!)

   (b) If 0.01 M of each of the following ions is in the solution, which will form a precipitate? (Select all that apply.)

      Hg2+    Fe2+    Mn2+    Ni2+    K+     Pb2+     Ag+    Cu2+

Hint: First, calculate [HS-] produced by the dissociation of H2S from the given concentrations of HCl and H2S. Second, calculate [OH-] from the given concentration of HCl. Then calculate Qsp for each of the metal sulfides. Remember, sulfides have unique solubility equilibria.

1.) What is the pH of a buffer that consists of 0.43 M CH3NH2 and 0.90 M CH3NH3Cl? (pKb of methylamine (CH3NH2) = 3.35.) 2.) Find the pH during the titration of 20.00 mL of 0.2360 M benzoic acid, C6H5COOH (Ka = 6.3 X 10^7) 5.) In a qualitative analysis procedure, a chemist adds HCl to an unknown group of ions and then saturates the solution with H2S so that the solution is 0.4 M in HCl and 0.10 M in H2S. a) What is the [HS -] of the solution? (Note: The answer should be rounded to one significant figure. Be careful, 3.5 rounds up to 4, but 4.5 rounds down to 4!) (b) If 0.01 M of each of the following ions is in the solution, which will form a precipitate? (Select all that apply.) Hg2+ Fe2+ Mn2+ Ni2+ K+ Pb2+ Ag+ Cu2+ Hint: First, calculate [HS-] produced by the dissociation of H2S from the given concentrations of HCl and H2S. Second, calculate [OH-] from the given concentration of HCl. Then calculate Qsp for each of the metal sulfides. Remember, sulfides have unique solubility equilibria. X 10^-17 and Kf of Ag(NH3)2+ = 1.7 X 10^-3M K2CrO4? Assume no volume change. (NOTE: Only ONE submission is allowed for the first part of this question.) Qsp ? Ksp ? 4.) Find the solubility of AgI in 3.6 M NH3. (Ksp of AgI = 8.3 X 10^-5 g of AgNO3 is dissolved in 15 mL of 5.4 X 10^-5), with 0.2360 M NaOH solution after the following additions of titrant. (a) 0 mL (b) 10.00 mL (c) 15.00 mL (d) 20.00 mL (e) 25.00 mL 3.) Does any solid Ag2CrO4 form when 1.7

Explanation / Answer

1.

pOH = pKb + log (salt/base)
pOH = 3.35 + log (0.9/0.43)
pOH = 3.67

2.
moles acid = 0.02000 L x 0.2360 M = 0.00472
[a].0ml

moles NaOH = 0 L x 0.1000 M = 0
Moles OH- in excess = 0.00472 - 0 =0.00472
total volume = 20.00 + 0ml = 20.0 mL = 0.020 L
[OH-]= 0.00472 / 0.020 =0.236 M
pOH = - log 0.236 = 0.627
pH = 14 - pOH = 13.37

[b]. 10ml

moles NaOH = 0.010 L x 0.1000 M = 0.001
Moles OH- in excess = 0.00472 - 0.001 =0.00372
total volume = 20.00 + 10ml = 30.0 mL = 0.030 L
[OH-]= 0.00372 / 0.030 =0.124 M
pOH = - log 0.236 = 0.907
pH = 14 - pOH = 13.09

[c]. 15ml

As above , you can similarly find for differnt concerntraion of titrant

I'll try and post other parts

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