Question

For each of the following buffer problems, start by writing out the relevant salt dissolution equation and then relevant acid/conjugate base equation. Then do the appropriate calculations to determine the amounts of each material that will be needed to make the solution.

1. 1.00 L of 0.20 M Phosphate buffer, pH=7.20, from K2HPO4 (FW=174.18) and either 6.0M HCl or 6.0M NaOH

2. 1.00 L of 0.15 M carbonate buffer, pH 10.00, from the salt NaHCO3 (FW=84.01) and either 8.0M HCl or 8.0M NaOH (pKa of carbonic acid= 3.77)

3. 1.00L of 0.70M TRIS buffer, pH 7.60, from Trizma base (FW=121.1) and 12.0M HCl. pKa=8.08

Answer #1

1. The no. of moles of phosphate buffer = 1 L * 0.2 M, i.e. 0.2 mol

K_{2}HPO_{4}
2K^{+} + HPO_{4}^{2-}

HPO_{4}^{2-} + H^{+}
H_{2}PO_{4}^{-}

According to Henderson-Hasselbalch equation, pH = pKa +
Log(n_{HPO42-} / n_{H2PO4-}),
where n = no. of moles

i.e. 7.2 = 7.2 + Log(n_{HPO42-} /
n_{H2PO4-})

i.e. Log(n_{HPO42-} /
n_{H2PO4-}) = 0

i.e.n_{HPO42-} =
n_{H2PO4-}

Here, _{HPO42-} + n_{H2PO4} = 0.2

Therefore, n_{HPO42-} =
n_{H2PO4-} = 0.1 mol

i.e. n_{HPO42-} = 0.1 mol * 174.18 g/mol, i.e. 17.418
g

Similarly, you can calculate for problems 2 and 3. All the very best !!!!!

Given the following list of common buffer systems available to
you in your lab, how would you prepare a system with a pH of
7.70?
HEPES pKa = 7.56
HEPPS pKa = 7.96 TRIS·
HCl pKa = 8.07
A.Using HEPES solution, add NaOH to raise the pH to 7.70
B.Using HEPES solution, add HCl to lower the pH to 7.70
C.Using HEPPS solution, add HCl to lower the pH to 7.70
D.Using HEPPS solution, add NaOH to raise the pH...

The Henderson-Hasselbalch equation relates the pH of a buffer
solution to the pKa of its conjugate acid and the ratio of
the concentrations of the conjugate base and acid. The equation is
important in laboratory work that makes use of buffered solutions,
in industrial processes where pH needs to be controlled, and in
medicine, where understanding the Henderson-Hasselbalch equation is
critical for the control of blood pH.
Part A.) As a technician in a large
pharmaceutical research firm, you need...

The Henderson-Hasselbalch equation relates the pH of a buffer
solution to the pKa of its conjugate acid and the ratio of
the concentrations of the conjugate base and acid. The equation is
important in laboratory work that makes use of buffered solutions,
in industrial processes where pH needs to be controlled, and in
medicine, where understanding the Henderson-Hasselbalch equation is
critical for the control of blood pH.
Part A
As a technician in a large pharmaceutical research firm, you need...

1.) An aqueous solution contains 0.23 M
hydrofluoric acid.
One Liter of this solution could be converted into a buffer by the
addition of:
(Assume that the volume remains constant as each substance is
added.)
0.12 mol HClO4
0.23 mol KNO3
0.24 mol HClO4
0.24 mol KF
0.117 mol NaOH
2.)
An aqueous solution contains 0.34 M
ammonia.
One liter of this solution could be converted into a buffer by the
addition of:
(Assume that the volume remains constant as...

1) A buffer contains significant amounts of ammonia and ammonium
chloride.
Part A
Write an equation showing how this buffer neutralizes added acid
(HI).
Express your answer as a chemical equation.
Part B
Write an equation showing how this buffer neutralizes added base
(CsOH).
Express your answer as a chemical equation.
2)
Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a
buffer with pH = 10.20.
Express your answer using two significant figures.
3) A 1.0-L buffer solution...

1.) You will work with 0.10 M acetic acid and 17 M acetic acid
in this experiment. What is the relationship between concentration
and ionization? Explain the reason for this relationship
2.) Explain hydrolysis, i.e, what types of molecules undergo
hydrolysis (be specific) and show equations for reactions of acid,
base, and salt hydrolysis not used as examples in the introduction
to this experiment
3.) In Part C: Hydrolysis of Salts, you will calibrate the pH
probe prior to testing...

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