You are asked to prepare 500 mL 0.300 M500 mL 0.300 M acetate buffer at pH 4.904.90 using only pure acetic acid ( MW=60.05 g/mol,MW=60.05 g/mol, pKa=4.76), pKa=4.76), 3.00 M NaOH,3.00 M NaOH, and water. Answer the questions regarding the preparation of the buffer. 1. How many grams of acetic acid will be needed to prepare the 500 mL buffer? Note that the given concentration of acetate refers to the concentration of all acetate species in solution.

Answers

Answer 1
Answer:

The quantity of acetic acid that is needed to prepare the 500 mL buffer is 9.0075 grams.

Given the following data:

  • Volume of acetate buffer = 500 mL to L = 0.5 L.
  • Molarity of acetate buffer = 0.300 M.
  • pH = 4.90.
  • MW = 60.05 g/mol.
  • pKa = 4.76.

How to calculate the mass of acetic acid.

First of all, we would write the equilibrium chemical reaction for acetate-acetic acid as follows:

                                CH_3COOH \rightleftharpoons CH_3COO^(-)+H^+

Next, we would calculate HA by applying Henderson-Hasselbalch equation:

pH =pka+ log_(10) (A^-)/(HA)

Where:

  • HA is acetic acid.
  • A^-  is acetate ion.

Substituting the given parameters into the formula, we have;

4.90 =4.76+ log_(10) (A^-)/(HA)\n\n4.90 -4.76+ log_(10) (A^-)/(HA)\n\n(A^-)/(HA)=1.38\n\nA^- = 1.38[HA]

For the concentration of both acids, we have:

[HA]+[A^-]=0.300M\n\n[HA]+1.38[HA]=0.300M\n\n2.38[HA]=0.300M\n\nHA = 0.126

For acetate ion:

A^- = 1.38[HA] = 1.38 * 0.126\n\nA^- =0.174

At a volume of 0.5 liters, we have:

HA = 0.5 * 0.126\n\nHA = 0.063 \;moles

A^- =  0.5 * 0.174\n\nA^- =0.087 \;moles

By stoichiometry:

Total moles = 0.063 + 0.087 = 0.15 moles.

Mass = number \;of \;moles * molar\;mass\n\nMass =0.15 * 60.05

Mass = 9.0075 grams.

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Answer 2
Answer:

Answer:

You will need 9,0 g of acetic acid

Explanation:

The equilibrium acetate-acetic acid is:

CH₃COOH ⇄ CH₃COO⁻ + H⁺ pka = 4,76

Using Henderson-Hasselbalch you will obtain:

pH = pka + log₁₀([A^(-)])/([HA])

Where HA is acetic acid and A⁻ is acetate ion

4,90 = 4,76 + log₁₀([A^(-)])/([HA])

1,38 = ([A^(-)])/([HA])(1)

As acetate concentration is 0,300M:

0,300M = [HA] + [A⁻] (2)

Replacing (2) in (1):

[HA] = 0,126 M

And:

[A⁻] = 0,174 M

As you need to produce 500 mL:

0,5 L × 0,126 M = 0,063 moles of acetic acid

0,5 L × 0,174 M = 0,087 moles of acetate

To produce moles of acetate from acetic acid:

CH₃COOH + NaOH → CH₃COO⁻ + Na⁺ + H₂O

Thus, moles of acetate are equivalents to moles of NaOH and all acetates comes from acetic acid, thus:

0,087 moles of acetate + 0,063 moles of acetic acid  ≡ 0,15 moles of acetic acid ×(60,05 g)/(1mol) = 9,0 g of acetic acid

I hope it helps!


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1. The atomic number of an element isdetermined by the number of:
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Be sure to answer all parts. A baseball pitcher's fastballs have been clocked at about 97 mph (1 mile = 1609 m). (a) Calculate the wavelength of a 0.148−kg baseball (in nm) at this speed. × 10 nm (Enter your answer in scientific notation) (b) What is the wavelength of a hydrogen atom at the same speed? nm

Answers

Answer:

a) The wavelength of the baseball is 1.033* 10^(-25) nm.

b) 9.131 nm is the wavelength of a hydrogen atom at the 43.35 m/s.

Explanation:

Velocity of the baseball = v = 97 mile/hour

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1 hour = 3600 seconds

v =(97* 1609 m)/(3600 s)=43.35 m/s

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=(6.626* 10^(-34) Js)/(0.148 kg* 43.35 m/s)

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The wavelength of the baseball is 1.033* 10^(-25) nm.

b)

Mass of the hydrogen atom = m=1.674* 10^(-27) kg

Velocity of hydrogen atom = u = 43.35 m/s

\lambda =(h)/(mv)    De Broglie wavelength

=(6.626* 10^(-34) Js)/(1.674* 10^(-27) kg* 43.35 m/s)

\lambda =9.131* 10^(-9) m

1 m=10^9 nm

\lambda =9.131 nm

9.131 nm is the wavelength of a hydrogen atom at the 43.35 m/s.

Final answer:

To calculate the wavelength of the baseball and hydrogen atom, we can use the wavelength formula. However, the wavelengths calculated are extremely small and cannot be practically detected.

Explanation:

To calculate the wavelength of the baseball, we can use the wavelength formula: λ = v/f. In this case, the velocity (v) of the baseball is given as 97 mph, which is equal to 97 * 1609 m/h. The frequency (f) can be calculated by dividing the speed of light (3 * 10^8 m/s) by the wavelength of the baseball.

For the hydrogen atom, we can use the same formula. However, we need to convert the hydrogen atom velocity to m/s. Once we have the velocity in m/s, we can calculate the wavelength by dividing the velocity by the frequency.

It is important to note that the wavelength calculated for the baseball and hydrogen atom are extremely small and cannot be practically detected by our senses or instruments.

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Answers

Final answer:

Molarity is a measure of concentration in a solution.


Explanation:

Molarity is a measure of concentration in a solution. It represents the amount of a solute dissolved in a given volume of solvent. Molarity is calculated by dividing the moles of solute by the volume of the solution in liters.


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