please I need help to solve this problem in quantum but I needed in detail is 2
ID: 924322 • Letter: P
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please I need help to solve this problem in quantum but I needed in detail is 2 part CHEM 2211 Fall 2015 Exam 3 Study Questions ic acid with a K, value of 1.44 x 10. A student prepared 100.0 mL 1. Valeric acid is a monoprotic acid with a K, value of 1.44 of a 0.200 M solution of valeric acid. a. What is the pH of the valeric acid solution? b. Suppose point of this titration? c. Choose an indicator for this titration and describe the the end point of the titration. is the ph rn is titrated with 0.200 M NaOH. What will be the pi at the equivalence of this titratotor for this titration and describe the color change that would be observed at this solution is titrated with 0.200 M 2. Consider the titration of 0.150 M carbonic acid with 0.150 M a. What is the initial pH of the carbonic acid solution?50 M NaoH. b. What is the pH at the first equivalence point of this titration? c. What is the pH at the second equivalence point of this titration? d. Choose an indicator suitable for detection of the first change that would be observed. e. Choose an indicator for detection change that would be observed. with 0.150 M NaOH indicator suitable for detection of the first equivalence point and describe the color of the second equivalence point and describe the color to contain 0.500 M propanoic acid, HC,HsO2, and 1.00 M sodium 3. A solution was prepared propionate, NaC3HsO2. a. What is the pH of this solution? b. Suppose 0.100 mole of NaOH is added to 1.00 resulting solution? b.Suppose 0.100 mole of NaOH is added to 1.00 L of the solution in (a). What i L of the solution in (a). What is the pH of th 4. a Write the mass balance and charge balance equations based on the following simultaneou equilibria: 21 (ea) Pbla(s) Pb)21 (a) b. Consider the ionization reactions of phosphoric acid, HsPO4. Write the three equation these ionization reactions. Write the charge balance and mass balance equations for this simultaneous equilibria.Explanation / Answer
1. a. acid dissociates to H+ and A-, let x amount has dissociated then,
Ka = [H+][A-]/[HA] = x^2/[HA]
1.44 x 10^-5 = x^2/0.2
x = [H+] = 1.70 x 10^-3 M
pH = -log[H+] = 2.77
b. titrated with 0.2 M NaOH - equivalence point
Volume of NaOH added = 0.2 x 0.1/0.2 = 0.1 L
[A-] = 0.02/0.2 = 0.1 M
salt hydrolysed in water, let x amount has hydrolyzed then,
A- + H2O ---> HA + OH-
Kb = Kw/Ka = 1 x 10^-14/1.44 x 10^-5 = x^2/0.1
x = [OH-] = 1.2 x 10^-10 M
pOH = 9.921
pH = 14 - pOH = 4.08
(c) An indicator which has pH range is around 4.08 would be best, Methyl organce has a range which matches with our need.
2. (a) initial pH
H2CO3 <==> H+ + HCO3-
Ka1 = 4.3 x 10^-7 = [H+][HCO3-]/[H2CO3]
let x amount has dissociated
4.3 x 10^-7 = x^2/0.15
x = [H+] = 2.54 x 10^-4 M
pH = 3.60
(b) pH at first equivalence point
pH = pKa1 + pKa2/2 = 6.35 + 10.33/2 = 8.34
(c) pH at second equivalence point
Volume of base added = 0.15/0.15 = 1 L
[CO3^2-] = 0.15/2 = 0.075 M
salt hydrolysed in water,
Kb2 = Kw/Ka2 = 1 x 10^-14/5.6 x 10^-11 = x^2/0.075
x = [OH-] = 3.66 x 10^-3 M
pOH = 2.44
pH = 14 - pOH = 11.56
(d) Indicator for this titration would be cresol red for first equivalence point
(e) Indicator for this titration would be alizarin yellow R for the second equivalence point
3. (a) pH = pKa + log([base]/[acid]
[base] = 1.0 M
[acid] = 0.5 M
pH = 4.87 + log(1/0.5) = 5.17
(b) moles of base NaOH added = 0.1 mols
the change in concentrations would be,
[base] = 1 M x 1 L + 0.1 mols/1 = 1.1 M
[acid] = 0.5 M x 1 L - 0.1/1 = 0.4 M
New pH would be,
pH = 4.87 + log(1.1/0.4) = 5.31
4. (a) charge balance : [Pb2+] = [I-] + [PbI3-]
Mass balance : 2[Pb2+] = [I-] + [PbI3-]
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