Question

Write a procedure so a lab mate could prepare 100 mL of buffer solution of that pH from two solids. Your procedure should clearly indentify which glassware and chemicals you will use to prepare the solution. Assume that you will use the sodium salt of the conjugate base to prepare the solution. Our desired pH is 7.5 and the weak acid I chose is Sodium hydrogen sulfite with pKa of 7.21.

Use Henderson-Hasselbalch equation to determine molequantities of the weak acid and its conjugate base that you will need to prepare the solution.

Calculate the masses of the weak acids and its conjugate base needed to get the correct pH.

Write a 5-8 step detailed procedure that explains how to actually prepare the buffer solution.

Answer #1

The conjugate base of hydrogen sulphite is sulphate.

Now, using the Henderson-Hasselbach equation, we can calculate the acid/base ratio:

If you choose sodium hydrogen sulphite and sodium sulphate.

The mass ratio is:

You need to prepare a buffer for biochemistry lab. The required
solution is 0.5Msodium phosphate, pH 7.0. Use the
Henderson-Hasselbalch equation to calculate the number of moles and
grams of moobasic sodium phosphate ( NaH2PO4) and dibasic sodium
phosphate ( Na2HPO4) necessary to make 1 liter of solution. The pKa
for this buffer is 7.21

Prepare a buffer by direct addition.
Consider how best to prepare one
liter of a buffer solution with pH = 3.62 using one of the weak acid/conjugate base
systems shown here.
Weak Acid
Conjugate Base
Ka
pKa
HC2O4-
C2O42-
6.4 x 10-5
4.19
H2PO4-
HPO42-
6.2 x 10-8
7.21
HCO3-
CO32-
4.8 x 10-11
10.32
How many grams of the sodium salt of the weak acid
must be combined with how many grams of the sodium
salt of its conjugate...

Consider how best to prepare one liter of a buffer solution with
pH = 8.09 using one of the weak acid/conjugate
base systems shown here.
Weak Acid
Conjugate Base
Ka
pKa
HC2O4-
C2O42-
6.4 x 10-5
4.19
H2PO4-
HPO42-
6.2 x 10-8
7.21
HCO3-
CO32-
4.8 x 10-11
10.32
How many grams of the sodium salt of the weak acid
must be combined with how many grams of the sodium
salt of its conjugate base, to produce 1.00 L of...

Consider how best to prepare one liter of a buffer solution with
pH = 6.55 using one of the weak acid/conjugate
base systems shown here.
Weak Acid
Conjugate Base
Ka
pKa
HC2O4-
C2O42-
6.4 x 10-5
4.19
H2PO4-
HPO42-
6.2 x 10-8
7.21
HCO3-
CO32-
4.8 x 10-11
10.32
How many grams of the sodium salt of the weak acid
must be combined with how many grams of the sodium
salt of its conjugate base, to produce 1.00 L of...

you need to prepare a buffer solution with a ph of 7.8. A lab
mate tells you to use N-2-
hydroxyethylpiperazine-N'-2-ethanesulfonic acid(HEPES), a sulfonic
acid with a pka of 7.5. since you know that the buffer pka should
be close to the desired pH, this sounds good. You make the solution
according to the following recipe, which is supposed to make 600 ml
of a 0.5 M solution:
dissolve 0.2 moles of HEPES in 400 ml of water. add 0.1...

Consider how best to prepare one liter of a buffer solution with
pH = 10.92 using one of the weak acid/conjugate
base systems shown here.
Weak Acid
Conjugate Base
Ka
pKa
HC2O4-
C2O42-
6.4 x 10-5
4.19
H2PO4-
HPO42-
6.2 x 10-8
7.21
HCO3-
CO32-
4.8 x 10-11
10.32
How many grams of the potassium salt of the weak
acid must be combined with how many grams of the
potassium salt of its conjugate base, to produce
1.00 L of...

Consider how best to prepare one liter of a buffer solution with
pH = 11.12 using one of the weak acid/conjugate
base systems shown here.
Weak Acid
Conjugate Base
Ka
pKa
HC2O4-
C2O42-
6.4 x 10-5
4.19
H2PO4-
HPO42-
6.2 x 10-8
7.21
HCO3-
CO32-
4.8 x 10-11
10.32
How many grams of the potassium salt of the
weak acid must be combined with how many grams of
thepotassium salt of its conjugate base, to
produce 1.00 L of...

To prepare 100 mL of 25 mM Tris buffer at pH 8.0, calculate
the amount of Tris base and Tris·HCl needed to make the buffer.
(Hint: find out the pKa of Tris·HCl and use the
Henderson-Hasselbalch Equation.) Describe how do you want to make
the solution, including how much water to add, how to adjust pH,
etc.

2) Two students want to prepare 2.0 L of a buffer solution which
must be buffered at a pH of 4.75. Student A wants to use acetic
acid (CH3COOH, Ka = 1.8 x 10-5) and sodium acetate to prepare the
buffer solution, while student B wants to use formic acid (HCOOH,
Ka = 1.8 x 10-4) and sodium formate.
Which student chose the better conjugate acid-base pair to
prepare the buffer? Why?
Explain the step-by- step procedure that the students...

Prepare a buffer by acid–base reactions.
Consider how to prepare a buffer solution with pH =
9.31 (using one of the weak acid/conjugate base
systems shown here) by combining 1.00 L of a
0.316-M solution of weak acid with
0.351 M potassium hydroxide.
Weak Acid
Conjugate Base
Ka
pKa
HNO2
NO2-
4.5 x 10-4
3.35
HClO
ClO-
3.5 x 10-8
7.46
HCN
CN-
4.0 x 10-10
9.40
How many L of the potassium hydroxide solution
would have to be added...

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