Question

1.What volume of a 1.50 M NaOH solution should be added to 50.0
mL of 1.20 M acetic acid (CH_{3}CO_{2}H;
K_{a} = 1.76×10^{-5}) to obtain a buffer with pH =
5.450?

a) 33.3 mL

b) 6.70 mL

c) 16.4 mL

d) 67.0 mL

e) 42.1 mL

2. Find the concentration of hydronium ion,
H_{3}O^{+}, in a 0.200 M solution of sodium
hypochlorite, NaOCl.

K_{a}(HOCl) = 3.0×10^{-8}.

a) 7.8×10^{-5} M

b) 1.3×10^{-10} M

c) 1.0×10^{-7} M

d) 3.9×10^{-11} M

e) 2.6×10^{-4} M

3. Consider a buffer solution made of 0.155 M acetic acid,
CH_{3}COOH, and 0.205 M sodium acetate,
NaCH_{3}COO. K_{a}(CH_{3}COOH) = 1.8 x
10^{-5}. After addition of 0.030 moles of NaOH to 1.0 L of
this buffer, the pH becomes [X]. *Fill in the*
*blank. Show the number only. Report with 2 digits after the
decimal point.*

4. Nitrous acid, HNO_{2}, has the K_{a} =
7.1×10^{-4}. The pH of a 0.1750 M solution of nitrous acid
is [X]. (*Fill in the blank*. Report with correct
number of significant figures).

5. A 1.25 M solution of chlorous acid, HClO_{2}, is 9.2%
dissociated. What is the pH of this solution?

a) 1.13

b) 0.94

c) 2.16

d) 0.64

e) 0.097

6. What is the pH of a buffer solution that is 0.20 M in
dimethylamine, (CH_{3})_{2}NH, and 0.30 M in
dimethylammoniumchloride,
(CH_{3})_{2}NH_{2}Cl? For
(CH_{3})_{2}NH, K_{b} =
5.95×10^{-4}.

a) 3.05

b) 3.40

c) 10.92

d) 9.89

e) 10.59

Answer #1

1. Using Hendersen-Haselbalck equation,

pH = pKa + log(base/acid)

5.45 = 4.76 + log(x/1.2 x 50 - x)

300 - 5x = x

moles of NaOH required = x = 300/6 = 50 mmol

Volume of NaOH = 50/1.5 = 33.3 ml

Answer: 1) 33.3 ml

2. OCl- + H2O <==> HOCL + OH-

Kb = 3.5 x 10^-8 = x^2/0.2

x = [OH-] = 8.37 x 10^-5 M

[H3O+] = 1 x 10^-14/8.37 x 10^-5 = 1.3 x 10^-10 M

Answer : B) 1.3 x 10^-10 M

3. ph after addition of NaOH

pH = 4.76 + log[(0.155 + 0.03)/(0.205 - 0.03)]

= 4.72

4. HNO2

7.1 x 10^-4 = x^2/0.1750

x = [H3O+] = 1.11 x 10^-2 M

pH= -log[H3O+] = 2.00

5. pH = -log(0.092 x 1.25) = 0.94

Answer: B) 0.94

6. pH = 3.27 + log(0.2/0.3) = 3.05

Answer : a) 3.05

Consider a buffer solution made of 0.255 M acetic acid,
CH3COOH, and 0.165 M sodium acetate,
CH3COONa. Ka(CH3COOH) =
1.8×10-5. After addition of 0.040 moles of NaOH to 1.0 L
of this buffer, the pH becomes [X]. Fill in the
blank. Show the number only. Report with 2 digits after the
decimal point.

You have 500.0 mL of a buffer solution containing 0.20 M acetic
acid (CH3COOH) and 0.30 M sodium acetate
(CH3COONa). What will the pH of this solution be after
the addition of 20.0 mL of 1.00 M HCl solution? Ka for
acetic acid = 1.8 × 10–5

25.00 mL of 0.1 M acetic acid are titrated with 0.05 M NaOH.
Calculate the pH of the solution after addition of 25 mL of NaOH.
Ka(CH3COOH) = 1.8 x 10-5.

1. Determine the volume in mL of 0.2 M NaOH(aq) needed
to reach halfway to the equivalence (stoichiometric) point in the
titration of 31 mL of 0.21 M propanoic acid(aq). The Ka
of propanoic acid is 1.3 x 10-5.
2. Determine the pH at the equivalence (stoichiometric)
point in the titration of 26 mL of 0.15 M
(CH3)2NH(aq) with 0.2 M HCl(aq). The
Kbof (CH3)2NHis 5.4 x
10-4.
Please Help me these questions!

An aqueous solution contains 0.387 M
dimethylamine
((CH3)2NH).
How many mL of 0.258 M perchloric
acid would have to be added to 225 mL of
this solution in order to prepare a buffer with a pH of
10.400.

An aqueous solution contains 0.355 M
dimethylamine
((CH3)2NH).
How many mL of 0.298 M hydrochloric
acid would have to be added to 125 mL of
this solution in order to prepare a buffer with a pH of
10.800.

a) What is the pH of a solution prepared by adding 25.0 mL of
0.10 M acetic acid (Ka=1.8 x 10^-5) and 20.0 mL of 0.10 M sodium
acetate?
b) What is the pH after the addition of 1.0 mL of 0.10 M HCl to
20 mL of the solution above?
c) What is the pH after the addition of 1.0 mL of 0.10 M NaOH to
20 mL of the original solution?

A quantity of 26.4 mL of a 0.45 M acetic acid (CH3COOH) solution
is added to a 31.9 mL of a 0.37 M sodium hydroxide (NaOH) solution.
What is the pH of the final solution?

A buffer solution that is 0.10 M sodium acetate and 0.20 M
acetic acid is prepared. Calculate the initial pH of this solution.
The Ka for CH3COOH is 1.8 x 10-5 M. As usual, report pH to 2
decimal places.
Calculate the pH when 21.1 mL of 0.014 M HCl is added to 100.0
mL of the above buffer.

A 1.0 0Liter buffer solution is .760 M acetic acid and .350 M in
sodium acetate. Calculate the pH of the solution after the addition
of 100 mL of 0.500 M HCl. The Ka for acetic acid is 1.8 * 10^-5

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