1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
andre [41]
3 years ago
13

A beaker with 135 mL of an acetic acid buffer with a pH of 5.000 is sitting on a benchtop. The total molarity of acid and conjug

ate base in this buffer is 0.100 M. A student adds 5.70 mL of a 0.490 M HCl solution to the beaker. How much will the pH change
Chemistry
1 answer:
asambeis [7]3 years ago
8 0

Answer:

pH = 4.64

Explanation:

To find the pH of a buffer solution we need to use the Henderson-Hasselbalch equation:

pH = pKa + log(\frac{[CH_{3}COO^{-}]}{[CH_{3}COOH]})

<u>We have</u>:

pKa = 4.76

pH_{i} = 5.00

[CH₃COOH] + [CH₃COO⁻] = 0.100 M

V = 135 mL = 0.135 L  

To find the pH after the student adds the solution of HCl, first, we need to find the concentrations of the acetic acid and acetate (conjugate base). To do that we will calculate the number of moles before and after the addition of HCl solution.  

Before the addition of the HCl solution we have:

pH = pKa + log(\frac{[CH_{3}COO^{-}]}{[CH_{3}COOH]})

5.00 = 4.76 + log(\frac{[CH_{3}COO^{-}]}{[CH_{3}COOH]})

\frac{[CH_{3}COO^{-}]}{[CH_{3}COOH]} = 1.74

[CH_{3}COO^{-}] = 1.74*[CH_{3}COOH]    (1)

Also we have that the total molarity of acid and conjugate base in this buffer is 0.100 M:

[CH_{3}COOH] + [CH_{3}COO^{-}] = 0.100 M   (2)

Solving equation (1) and (2) for [CH₃COOH] and [CH₃COO⁻], we have:

[CH₃COOH] = 0.036 M

[CH₃COO⁻] = 0.064 M

Now, the number of moles of the acid and conjugate base is:  

\eta_{[CH_{3}COOH]} = 0.036 mol/L*0.135 L = 4.86 \cdot 10^{-3} moles

\eta_{[CH_{3}COO^{-}]} = 0.064 mol/L*0.135 L = 8.64 \cdot 10^{-3} moles

                                 

After the addition of HCl solution we have:

\eta_{HCl} = 0.490 M*5.70 \cdot 10^{-3} L = 2.79 \cdot 10^{-3} moles

The HCl added will react with the conjugate base of the acetic acid:

            H₃O⁺   +    CH₃COO⁻     ⇄     CH₃COOH   +    H₂O      

2.79x10⁻³moles   8.64x10⁻³moles                                  

From the reaction of HCl with CH₃COO⁻ we have:

\eta_{CH_{3}COO^{-}} = 8.64 \cdot 10^{-3} moles - 2.79\cdot 10^{-3} moles = 5.85 \cdot 10^{-3} moles

\eta_{CH_{3}COOH} = 4.86 \cdot 10^{-3} moles + 2.79 \cdot 10^{-3} moles = 7.65 \cdot 10^{-3} moles

Finally, we can find the pH of the solution after the addition of HCl:

V_{T} = 5.7 \cdot 10^{-3} L + 0.135 L = 0.141 L

pH = pKa + log(\frac{[CH_{3}COO^{-}]}{[CH_{3}COOH]})

pH = 4.76 + log(\frac{\eta_{CH_{3}COO^{-}}/V_{T}}{\eta_{CH_{3}COOH}/V_{T}})

pH = 4.76 + log(\frac{5.85 \cdot 10^{-3} moles/0.141 L}{7.65 \cdot 10^{-3} moles/0.141 L})

pH = 4.64

I hope it helps you!  

You might be interested in
4 b + 3 o2 → 2 b2o3 if 8 moles of b and 4 moles of o2 are allowed to react, how many moles of b2o3 can be formed?
raketka [301]

The number of moles of  b2o3 that will be formed is determined as 4 moles.

<h3>Limiting reagent</h3>

The limiting reagent is the reactant that will be completely used up.

4 b + 3O₂ → 2b₂O₃

from the equation above;

4 b ------------> 2 b₂O₃

2b ------------> b₂O₃

2 : 1

3O₂  -------------> 2b₂O₃

3  :  2

b is the limiting reagent, thus, the amount of b2o3 to be formed is calculated as;

4 b ------------> 2 moles of  b2o3

8 moles -------> ?

= (8 x 2)/4

= 4 moles

Thus, the number of moles of  b2o3 that will be formed is determined as 4 moles.

Learn more about limiting reactants here: brainly.com/question/14222359

#SPJ1      

6 0
2 years ago
Gravity is a force that helps to hold the universe together.
My name is Ann [436]

Mhm, it keeps the planets in place and circle around the Sun's gravitational pull, like how the Earth's small-like gravitational pull keeps the moon to circle around our planet,  and as a perk it makes the 80% water that around this whole place to have high and low tides.

- Sincerely, Ouma

7 0
3 years ago
Activation energy is (blank)
timurjin [86]

B. The energy barrier between reactants and products

hope this helps!

(:

7 0
3 years ago
Read 2 more answers
What is a factor that affects the outcome of an experiment?
Anni [7]

Answer:

Observation affects the outcome

7 0
3 years ago
Read 2 more answers
Use lewis theory to determine the formula for the compound that forms between sr and se
katen-ka-za [31]

\text{Sr}\text{Se}

<h3>Explanation</h3>

The Lewis Theory predicts the way atoms form bond based on their numbers of valence electrons. Atoms gain or lose electrons as they seek to achieve either a complete eight-electron valence shell or an empty shell, exposing the inner eight-electron shell. Both electron configurations are stable and are known as "octets". However, atoms tend to prefer the configuration with the minimum number of electron transfers.

Strontium (Sr) is found in group 2 (II A) of a modern periodic table. A neutral atom of strontium has two valence electrons in its valence shell.

Selenium (Se) is found in group 16 (VI A) of a modern periodic periodic table. A neutral atom of selenium contains six electrons in its valence shell.

Strontium needs to either lose two electrons or gain six electrons to achieve a configuration with eight electrons in its valence shell. Losing two electrons take less energy. Strontium is thus expected to lose two electrons.

Similarly, selenium would prefer gaining two electrons to losing six electrons. It is expected to gain two electrons.

As a result, a strontium atom would supply exactly two electrons. At the same time, a  As a result, a selenium atom would accept the two electrons, no more or no less. The two elements would combine at a one to one ratio. In other words:

n(\text{Sr, atoms}) : n(\text{Se, atoms}) \\= n(\text{Sr, electrons lost}) : n(\text{Se, electrons gained}) \\= 1:1

Each electron carries one negative charge. As a result, atoms that have gained electrons demonstrate a negative charge, whereas atoms that have lost electrons appear to be positive. By convention, atoms with a positive charge shall be written in front of those with a negative charge in a formula.

Sr atoms have lost electrons. Accordingly, they carry positive charges and shall be written at the beginning of the formula.

Se atoms have gained electrons. Accordingly, they carry negative charges and shall be placed to the end of the formula.

Thus the chemical formula: \text{Sr}\text{Se}

4 0
3 years ago
Other questions:
  • What is the mass of 1.0 x 10-3 mole of Zn? 3.9 x 1022 0.065 0.000015
    14·2 answers
  • How do you tell if a reaction is endothermic or exothermic using only the written formula
    13·1 answer
  • URGENT HELP PLEASE balance equation !20 points!
    5·1 answer
  • What are three ways heat is transfered
    8·2 answers
  • What’s the physical properties of a molecular solid, in regards to its physical properties of formation?
    8·1 answer
  • Ray puts a glass of ice water on the table. One hour later he observes that only water is left in the glass. What happened?
    7·2 answers
  • What is the mass of 0.25 mol of sulfur atom
    10·1 answer
  • Which of the following describes an energy transformation from chemical to electrical to light energy?
    12·2 answers
  • Sn=0.14 (E) <br>Sn+2 = -0.15(E) <br>Which form of tin is the stronger reducing agent? OS O Sn +2? ​
    10·1 answer
  • If the decomposition of a sample of k c l o 3 kclox3 produces 3. 29 g of o 2 ox2 , what was the mass (g) of the original sample?
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!