2) A 1000 ml sample of 0.20 M HE is itrated with 0.10 M KOH. Determine the pH of

Question

2) A 1000 ml sample of 0.20 M HE is itrated with 0.10 M KOH. Determine the pH of the solution 2) before the addition of any KOH. The Ka of HE is3510 B) 2.08 A) 3.46 C) 0.70 D) 1.00 E) 4.15 3) Calculate the pH of a solution that is 0.295 M in sodium formate (NaHCO2) and 0205 M in formic 3) acid (HCO2H). The Ka of formic acid is 1.77 104, C) 4.963 A) 13.84 B) 3.587 D) 10.10 E) 3.910 4) What is the pH of a solution made by mixing 10.00 mL of 0.10 M acetic acid with 10.00 mL of 0.10 M KOH? Assume that the volumes of the solutions are additive. Ka -1.8-10-5 for 4) CH3CO2H. A) 7.00 B) 8.72 C) 5.28 D) 10.02 5) Determine the molar solubility of CasO4 in a solution containing 0.100 M Na2So4 5) Ksp (Casos) -24 10-5 A) 4.9 10-3 M B) 24 10-4 M C)5.8 10-10 M D) 0.10 M E) 1.2 x 10-5 M 6) Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO2) 6) and 0.278 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50 10-4 A) 0.162 B) 15.5 C) 2.78 10-3 D) 3.448 E) 55.6

Explanation / Answer

2)

Before any addition of KOH there is only HF is present and pH of the compound is given by,

pH = 1/2(pka - logC)

pH = 1/2(-logpKa - logc)

pH = 1/2(-log(3.5*10^-4) - log(0.2*100/1000))

pH = 2.58

3)

The given mixture is buffer solution,

pH of buffer = pKa + log[salt]/[Acid]

pH = -log(1.77*10^-4) + log(0.295/0.205)

pH = 3.910

5)

CaSO4 ------> Ca+2 + SO42-

Ksp = [Ca+2][SO42-]

Ksp = (s)(s)

but the CaSO4 is present in the Na2SO4 solution,

Na2SO4 -----> 2 Na+ + SO4 2-

0.1M ------ 2*0.1M of Na+ and 0.1 M of SO42-

so concentration of SO42- is increases then,

CaSO4 -----> Ca+2 + SO4 2-

solubility    S     (S+0.1)

Ksp = [Ca+2][SO42-]

2.4*10^-5 = (s)(s+0.1)

s = solubility = 2.4*10^-4

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