Calculate the concentrations of acetic acid and sodium acetate in the buffer sol

ID: 811215 • Letter: C

Question

Calculate the concentrations of acetic acid and sodium acetate in the buffer solution you will prepare in the experiment:

Acetic acid concentration is _____________ M (2 dec places)

Sodium acetate concentration is ______________ M (2 dec places)

The theoretical pH of this buffer solution is (hint: use Henderson-Hasselbach) is ______________ (2 dec places).

Ka= 1.8 *10^-5

Buffer Solution In Ihe Beaker Contains:

50 mL of a 0.20M NaC2H3O2 stock solution

10 mL of a 1.0M HC2H3O2 stock solution

Water is added until the total volume = 100 mL

Given, 50mL of 0.20 M sodiu acetate

Moles of sodium acetate = Molarity x volume (inL) = 0.01 moles

Final volume = 100 mL = 0.1 L

[NaC2H3O2] = 0.01 mol / 0.1 L = 0.1 M

Thus, sodiun acetate concentration is 0.10 M

Given, 10mL of 1.0 M acetic acid

Moles of sodium acetate = Molarity x volume (inL) = 0.01 moles

Final volume = 100 mL = 0.1 L

[HC2H3O2] = 0.01 mol / 0.1 L = 0.1 M

Thus, Acetic acid concentration is 0.10 M

Henderson-Hasselbalch equation is

pH = pKa + log[Salt] / [Acid]

Given, Ka = 1.8 x 10^-5

pKa = -log Ka = 4.74

[Salt] = [Acid] = 0.10 M

pH = 4.74 + log [0.10 / 0.10]

pH = 4.74

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