Question

**Part A**

Consider a buffer solution that is 0.50 *M* in NH3 and
0.20 *M* in NH4Cl. For ammonia, p*K*b=4.75.

Calculate the pH of 1.0 L of the original buffer, upon addition of 0.190 mol of solid NaOH.

**Part B**

A 1.0-L buffer solution contains 0.100 mol HC2H3O2 and 0.100
mol NaC2H3O2. The value of *K*a for HC2H3O2 is
1.8×10−5.

Calculate the pH of the solution, upon addition of 0.030 mol of NaOH to the original buffer.

(I will leave a good rating, thank you)

Answer #1

part A)

NH4Cl + NaOH -------------> NH3 + NaCl + H2O

after 0.190/1.0 = 0.190 M NaOH added

[NH3] = 0.50 + 0.190 = 0.690 M

[NH4Cl] = 0.20 - 0.190 = 0.01 M

pOH = pKb + log [NH4Cl] / [NH3]

pOH = 4.75 + log [0.01] / [0.690]

pOH = 2.91

pH = 14 - 2.91

pH = 11.09

part B)

HC2H3O2 + NaOH -----------> NaC2H3O2 + H2O

up on addition of 0.030 / 1.0 = 0.030 M NaOH

[HC2H3O2] = 0.100 - 0.030 = 0.07 M

[NaC2H3O2] = 0.100 + 0.03 = 0.130M

pH = pKb + log [NaC2H3O2]/[HC2H3O2]

pKb = - log Kb = -log [1.8 x 10^{-5} ] = 4.74

pH = 4.74 + log [0.130] / [0.07]

pH = 5.01

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in
NH4Cl. For ammonia, pKb=4.75. You may want to reference (Pages 648
- 658) Section 16.2 while completing this problem. Part A Calculate
the pH of 1.0 L of the original buffer, upon addition of 0.030 mol
of solid NaOH. Express the pH to two decimal places.

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in
NH4Cl. For ammonia, pKb=4.75.
Calculate the pH of 1.0 L of the solution, upon addition of
36.00 mL of 1.0 MHCl.

1.) A buffer solution contains 0.455 M
NH4Cl and
0.295 M NH3
(ammonia). Determine the pH
change when 0.085 mol
NaOH is added to 1.00 L of the
buffer.
pH after addition − pH before addition = pH change
=
2.)
Determine the pH change when
0.044 mol HNO3 is
added to 1.00 L of a buffer solution that is
0.462 M in HF and
0.218 M in F-.
pH after addition − pH before addition = pH change
=

For the next three problems, consider 1.0 L of a solution which
is 0.3 M NH4Cl and 0.2 M NH3 (Ka for NH4Cl = 5.6 x 10-10). Assume 2
significant figures in all of the given concentrations so that you
should calculate all of the following pH values to two decimal
places. 1. Calculate the pH of this solution. 2. Calculate the pH
after 0.10 mol of HCl has been added to the original solution.
Assume no volume change on...

Consider a solution of 2.0 M HCN and 1.0 M NaCN (Ka for HCN =
6.2 x 10-10). Which of the following statements is true?
a) The solution is not a buffer because [HCN] is not equal to
[CN-]
b) The pH will be below 7.00 because the concentration of the
acid is greater than that of the
base.
c) [OH-] > [H+]
d) The buffer will be more resistant to pH changes from addition
of strong acid than to...

A buffer solution is prepared by mixing 50.0 mL of 0.300 M
NH3(aq) with 50.0 mL of 0.300 M NH4Cl(aq). The pKb of
NH3 is 4.74.
7.50 mL of 0.125 M NaOH is added to the 100.0 mL of the original
buffer solution prepared in Question 1 (no HCl added). Calculate
the new NH3 concentration for the buffer solution.
Calculate the new NH4Cl concentration for the buffer
solution.
Calculate the new pH of the solution.

A 1.0-L buffer solution contains 0.100 molHC2H3O2 and 0.100
molNaC2H3O2. The value of Ka for HC2H3O2 is 1.8×10−5. You may want
to reference (Pages 648 - 658) Section 16.2 while completing this
problem. Part A Calculate the pH of the solution upon addition of
48.1 mL of 1.00 MHCl to the original buffer.

A 100 mL of buffer solution contains 0.100 M in NH3 (aq) and
0.100 M in NH4Cl. (Q7 ‒ Q9)
7. Calculate pH of the buffer solution.
8. Calculate the change of pH when 4.00 mL of 0.100 M HCl (aq)
is added to the buffer solution.
9. Calculate the pH of the solution when 4.00 mL of 0.100 M NaOH
is added to the original buffer solution.
Please show steps and explain so I can understand how. thank
you

A 1.0 L buffer solution contains 0.192 MHC2H3O2 and 0.192 M
NaC2H3O2. The value of Ka for HC2H3O2 is 1.8×10−5. Because
the initial amounts of acid and conjugate base are equal, the pH of
the buffer is equal to pKa=−log(1.8×10−5)=4.74.
Calculate the new pH after adding 0.019 mol of solid NaOH to the
buffer.

３９．A buffer solution is 1.20 M in NH3 and 1.00 M in NH4Cl. If
0.190 moles of NaOH are added to 1.00 L of the buffer, what is its
pH? Assume the volume remains constant. Kb of NH3 = 1.8 ✕ 10-5.
ＴＫＳ

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