A beaker with 120mL of an acetic acid buffer with a pH of 5.00 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.1M. A student adds 6.60mL of a 0.300M HCl solution to the beaker. How much will the pH change?
The pKa of acetic acid is 4.76.
Chemistry Buffer Calculations
1 Answer
Stefan V.
May 8, 2016
Δ
pH
=
0.29
Explanation:
!! LONG ANSWER !!
The idea here is that you need to use the Henderson-Hasselbalch equation to determine the ratio that exists between the concentration of the weak acid and of its conjugate base in the buffer solution.
Once you know that, you can use the total molarity of the acid and of the conjugate base to find the number of moles of these two chemical species present in the buffer.
So, the Henderson-Hasselbalch equation looks like this
∣
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
pH
=
p
K
a
+
log
(
[
conjugate base
]
[
weak acid
]
)
a
a
∣
∣
∣
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
In your case, you have acetic acid,
CH
3
COOH
, as the weak acid and the acetate anion,
CH
3
COO
−
, as its conjugate base. The
p
K
a
of the acid is said to be equal to
4.76
, which means that you have
pH
=
4.76
+
log
(
[
CH
3
COO
−
]
[
CH
3
COOH
]
)
The pH is equal to
5
, and so
5.00
=
4.76
+
log
(
[
CH
3
COO
−
]
[
CH
3
COOH
]
)
log
(
[
CH
3
COO
−
]
[
CH
3
COOH
]
)
=
0.24
This will be equivalent to
10
log
(
[
CH
3
COO
−
]
[
CH
3
COOH
]
)
=
10
0.24
which will give you
[
CH
3
COO
−
]
[
CH
3
COOH
]
=
1.74
This means that your buffer contains
1.74
times more conjugate base than weak acid
[
CH
3
COO
−
]
=
1.74
×
[
CH
3
COOH
]
Now, because both chemical species share the same volume,
120 mL
, this can be rewritten as
n
C
H
3
C
O
O
−
120
⋅
10
−
3
L
=
1.74
×
n
C
H
3
C
O
O
H
120
⋅
10
−
3
L
which is
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
n
C
H
3
C
O
O
−
=
1.74
×
n
C
H
3
C
O
O
H
a
a
∣
∣
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
(
1
)
So, the buffer contains
1.74
times more moles of acetate anions that of acetic acid.
Now, the total molarity of the buffer is said to be equal to
0.1 M
. You thus have
[
CH
3
COOH
]
+
[
CH
3
COO
−
]
=
0.10 M
Once again, use the volume of the buffer to write
n
C
H
3
C
O
O
H
120
⋅
10
−
3
L
+
n
C
H
3
C
O
O
−
120
⋅
10
−
3
L
=
0.1
moles
L
This will be equivalent to
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
n
C
H
3
C
O
O
−
+
n
C
H
3
C
O
O
H
=
0.012
a
a
∣
∣
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
(
2
)
Use equations
(
1
)
and
(
2
)
to find how many moles of acetate ions you have in the buffer
1.74
⋅
n
C
H
3
C
O
O
H
+
n
C
H
3
C
O
O
H
=
0.012
n
C
H
3
C
O
O
H
=
0.012
1.74
+
1
=
0.004380 moles CH
3
COOH
This means that you have
n
C
H
3
C
O
O
−
=
1.74
⋅
0.004380 moles
n
C
H
3
C
O
O
−
=
0.007621 moles CH
3
COO
−
Now, hydrochloric acid,
HCl
, will react with the acetate anions to form acetic acid and chloride anions,
Cl
−
H
Cl
(
a
q
)
+
CH
3
COO
−
(
a
q
)
→
CH
3
COO
H
(
a
q
)
+
Cl
−
(
a
q
)
Notice that the reaction consumes hydrochloric acid and acetate ions in a
1
:
1
mole ratio, and produces acetic acid in a
1
:
1
mole ratio.
Use the molarity and volume of the hydrochloric acid solution to determine how many moles of strong acid you have
∣
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
c
=
n
solute
V
solution
⇒
n
solute
=
c
⋅
V
solution
a
a
∣
∣
∣
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
In your case, this gets you
n
H
C
l
=
0.300 mol
L
−
1
⋅
volume in liters
6.60
⋅
10
−
3
L
n
H
C
l
=
0.001980 moles HCl
The hydrochloric acid will be completely consumed by the reaction, and the resulting solution will contain
n
H
C
l
=
0 moles
→
completely consumed
n
C
H
3
C
O
O
−
=
0.007621 moles
−
0.001980 moles
=
0.005641 moles CH
3
COO
−
n
C
H
3
C
O
O
H
=
0.004380 moles
+
0.001980 moles
=
0.006360 moles CH
3
COOH
The total volume of the solution will now be
V
total
=
120 mL
+
6.60 mL
=
126.6 mL
The concentrations of acetic acid and acetate ions will be
[
CH
3
COOH
]
=
0.006360 moles
126.6
⋅
10
−
3
L
=
0.05024 M
[
CH
3
COO
−
]
=
0.005641 moles
126.6
⋅
10
−
3
L
=
0.04456 M
Use the Henderson-Hasselbalch equation to find the new pH of the solution
pH
=
4.76
+
log
(
0.04456
M
0.05024
M
)
pH
=
4.71
Therefore, the pH of the solution decreased by
Δ
pH
=
|
4.71
−
5.00
|
=
∣
∣
∣
∣
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
a
a
0.29 units
a
a
∣
∣
−−−−−−−−−−−−−
Answer link
Related topic
Buffer Calculations
Questions
Related questions
How are buffer solutions used?
How do you calculate buffer capacity?
How do buffer solutions maintain the pH of blood?
How do you buffer a solution with a pH of 12?
Why are buffer solutions used to calibrate pH?
What is the role of buffer solution in complexometric titrations?
How you would make 100.0 ml of a 1.00 mol/L buffer solution with a pH of 10.80 to be made using...
What is the Henderson-Hasselbalch equation?
What is an example of a pH buffer calculation problem?
Why is the bicarbonate buffering system important?
iOS
Android
Privacy
Terms
Help
why brain remembers picture better than words?
Answer:
your brain processes ever detail in a picture rather than words for for example a picture of something words doesn't describe it as well as the picture could.
Write a paragraph on "lipids as pigments".
Why do scientists use the scientific method?
A. It helps them do research that other scientists can understand.
B. It helps them ask questions that affect as many people as
possible.
C. It helps them make sure a certain question has not been asked
before.
OD. It helps them determine whether an idea is supported by evidence.
Help
Answer:
DExplanation:
It helps determine whether an idea is supported by evidencehope it helps please follow because I don't have any followers I have 0 followersA car goes from 0 to 100m/s in 10s what is that acceleration
Answer:
10m\s
Explanation:
given
initial velocity(u)=0
final velocity (v)=100
acceleration(a)=?
we know,
acceleration = v-u/t
= 100-0\10
= 10 m\s
What holds the nucleus together? Group of answer choices alpha particles strong forces electrical forces between the protons beta particles
Answer:electrical forces between the protons
Explanation: The strong nuclear force pulls together protons and neutrons in the nucleus. At very small distances only, such as those inside the nucleus, this strong force overcomes the electromagnetic force, and prevents the electrical repulsion of protons from blowing the nucleus apart.
Ensure you write the states of the reactants and products.
• phosphoric acid reacts with magnesium hydroxide
How many moles are contained in 127 grams of lead?
Answer:
18.015
Explanation:
What is the pressure exerted by a force of 15.0 N over an area of 0.00372 m^2 ?
Explanation:
Pressure = Force/Area
therefore,
P = 15/0.00372
= 4.03 X10^³N/m²
list 2 underlying causes of water pollution
Answer:
industrialization and rapid human population growth.
Explanation:
Hope this helps
Answer:
Water Pollution
Explanation:
Dumping industrial waste in ocean
Accidental oil leakages
What is the interaction between atmosphere and biosphere
Answer:
Biosphere-Atmosphere Interactions focuses on the sources and sinks of greenhouse gases (GHGs), air pollutants, particulate matter, water, and energy between the Earth's surface and the atmosphere.
Explanation:
17) An ethanol solution has a concentration of 0.500M. What volume in liters of this solution
would contain 8.0 moles of ethanol?
To calculate the Molar Concentration, we will find the molar concentration by dividing the moles by liters of water used in the solution. For example, the acetic acid here is completely dissolved in 1.25 L of water. Then divide 0.1665 moles by 1.25 L to get the molar concentration, which will be 0.1332 M.
Hope It Helpz(◕ᴥ◕)What physical property does salt have when it is dissolved in water?
And
What type of mixture is salt water?
Symbol of elements.
Explanation:
Gold Au
Copper Cu
Iron Fe
Magnesium Mg
Hydrogen H
Helium He
Mercury Hg
Iodine I
Which compound contains ionic bonds?
No
No2
CaO
CO2
Calculate the mass of diphosphorus pentoxide (P,05) that contains a trillion (1.000 x 10^2) phosphorus atoms. Be sure your answer has a unit symbol if necessary, and round it to 4 significant digits.
Answer: The answer is 94.25 × 10¯¹² g.
How do molecules work?
A molecule is essentially created by a collection of atoms linked by a network of bonds.
If 2.5 moles of PA react completely, how many
moles of P203 are formed?
Answer:
For every 2 moles of Na used, 2 moles of NaCl are produced.
Explanation:
when would a scientist choose to conduct a controlled experiment
Answer:a scientist would choose to conduct a controlled experiment when it has all the necessary precautions and has the equipment to do so
Explanation:thank you
Plz mark for brainlist
The boiling point of a liquid is tested at 10 different pressures, from 0.5 to 1.4 atmospheres. The results of the tests show that
there is a nearly constant increase in boiling point for each increase in pressure. Which conclusion is reasonable based on this
information? (1 point)
O A boiling point at 1.5 atmospheres could not be predicted with any certainty at all.
O A boiling point at 15 atmospheres could not be predicted with any certainty at all.
O A boiling point at 1.5 atmospheres could be predicted fairly well.
O A boiling point at 15 atmospheres could be predicted fairly well.
Since the increase in boiling point with increasing pressure is fairly constant, then, the boiling point at 1.5 atmospheres could be predicted fairly well.
We say that a substance has reached its boiling point when its pressure equals the atmospheric pressure. Recall that we can be able to make predictions from the results of an experiment.
In this case, we are told that there is a nearly constant increase in boiling point for each increase in pressure. Therefore, it is reasonable to conclude that, a boiling point at 1.5 atmospheres could be predicted fairly well.
Learn more: https://brainly.com/question/6284546
what is involved fashion of male and female gametes to form a zygote which develops into an embryo
Which of these challenges is unique to the process of designing prostheses as opposed to engineering other technologies?
- Knowing how a material will fail
- Using the engineering process
- Identifying a need for the technology
- Predicting how a technology will interact with human tissue
Answer:
predicting how a tech will interact with human tissue.
Explanation:
thats not really common except for in the medical field.
The challenge that is unique to the process of designing prostheses as opposed to engineering other technologies is Predicting how a technology will interact with human tissue. The correct option is option 4.
What is Prosthetic Design?Prosthesis design is typically undertaken by shaping wax on a plaster replica of the patient's anatomy. Realism is predominantly achieved through the prosthetist's ability to interpret the correct location and physically recreate the anatomical shape and detail.
Prosthetic applications are an example of the intersection of design, technology and science.
Therefore, The challenge that is unique to the process of designing prostheses as opposed to engineering other technologies is Predicting how a technology will interact with human tissue. The correct option is option 4.
Learn more about Prosthetic Design, here:
https://brainly.com/question/20548709
#SPJ3
The Universal Space Agency wants to know the results of your Sim investigation. Write your report to the lead chemist, explaining why drops of liquid water appeared on the outside of the cold, but not the warm, soda can. Use evidence from your investigation in your explanation.
Answer:
due to warm temperature
Explanation:
Explanation:
There is water present in liquid form instead of liquid nitrogen on the outer side of the can because of the temperature present in the surrounding environment. The temperature around the can is little warm which is favourable for the water but not for the liquid nitrogen. The liquid nitrogen present in liquid state when the temperature of the surrounding is too cold. if it is warm, the liquid nitrogen starts boiling and converts into gaseous state so that's why the warmer temperature is responsible for the presence of water not the liquid nitrogen.
Can someone help me with this please
Answer:
1.
a. Diagram A
b. Diagram A should stay still, but Diagram B should move/roll to the left.
__________________________________
2.
a. Diagram A and Diagram B are different because the object kg are different, one is 10kg and the other is 2kg.
b. Diagram B because its smaller making it lighter to move when Diagram A is 5 times larger, which will make it heavier.
__________________________________
3.
a. Diagram A and Diagram B compare because the object both equal 3kg.
b. Diagram A will have a greater acceleration because 80n > 40n
Anyone mind answering this
Explain in terms of chemical reactivity why the elements in group 18 on the modern periodic table were not identified by Mendeleev's at that time
Answer:
elements tend not to react with other elements, there were no oxide compounds for Mendeleev to study. –Group 18 elements are generally unreactive. sodium ion is smaller because the sodium atom lost one electron. –An Na+ ion is smaller because it has one fewer electron shell.
Explanation:
can you me as brainliest if its right? i just need a few more to rank up! ^-^
Also have a great day and good luck in your studies!
Your teacher asks you to prepare 500 mL of a 2.75 molar solution of NaCl for an upcoming
laboratory experiment. Write a step-by-step procedure describing how you would carry out
this task.
To prepare 500 mL of a 2.75 molar solution of NaCl, measure 80.44 g of NaCl, place it in a 500 mL volumetric flask and fill it with water to the mark.
We'll begin by calculating the number of mole of NaCl in the solution
Volume = 500 mL = 500 / 1000 = 0.5 L Molarity = 2.75 MMole of NaCl =?Mole = Molarity x Volume
Mole of NaCl = 2.75 × 0.5
Mole of NaCl = 1.375 mole
Next, we shall determine the mass of 1.375 mole of NaCl.
Mole of NaCl = 1.375 mole Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol Mass of NaCl =?Mass = mole × molar mass
Mass of NaCl = 1.375 × 58.5
Mass of NaCl = 80.44 g
Therefore, to prepare 500 mL of a 2.75 molar solution of NaCl, measure 80.44 g of NaCl, place it in a 500 mL volumetric flask and fill it with water to the mark.
Learn more about molarity: https://brainly.com/question/6685468
In the urea molecule, (NH2)2CO, both nitrogen atoms are bonded to the carbon atom. Each nitrogen atom has a lone pair. The molecular geometry is
Answer:
There are two -NH2 groups around the C=O. bond in the urea molecule structure. There are one lone pairs on each nitrogen atoms and two lone pairs on oxygen atom.
The molecule urea that the molecular geometry of the nitrogen atoms is tetrahedral.
What is molecular geometry?The term molecular geometry has to do with the arrangement of atoms around the central atom. On this case, we are looking at the arrangement of atoms around nitrogen.
We can see from the molecule urea that the molecular geometry of the nitrogen atoms is tetrahedral.
Learn more about urea:https://brainly.com/question/21133305
#SPJ2
need help with this question asap :)
-20 points!..
If the heat is added to an endothermic system, at equilibrium, the system will move to the _________ to regain equilibrium.
Answer:
At equilibrium, the system will move to the right to regain equilibrium
how many compounds can I make with sodium, hydrogen, oxygen?
will give brainliest and 100 points to the correct answer
Answer:
маны
Explanation:
Answer:
2H2 + O2 → 2H2O
Explanation:
