Question

A 0.100 mol/L solution of ethanoic acid has a pH of 2.960.

What percentage of the total ethanoic acid and ethanoate concentration consists of unionised ethanoic acid?
A) 98.9%
B) 1.01%
C) 33.8%
D) 66.2%

Answer 1

`\Huge \boxed{\boxed{\bf{A)\ 98.9\%}}}`

Step-by-step explanation:

We've been given the following information:

• pH of the solution (pH = 2.960)

• the concentration of ethanoic acid (0.100 mol/L).

We need to find out the percentage of the total ethanoic acid and ethanoate concentration that consists of unionized ethanoic acid.

1. Calculate [H+] Concentration

The pH of a solution can be calculated using the formula:

`\LARGE \boxed{\texttt{pH = -log[H+]}}}`

❖ [H+] is the concentration of H+ ions in mol/L.

Given the pH of 2.960, we can calculate [H+]:

`\large \boxed{\tt{[H+] = 10^(-pH)}}`

• 
  `\tt{[H+] = 10^(-2.960)}`

• 
  `\tt{[H+] = 0.00109647819}`

• 
  `\tt{[H+] = 1.09647819 * 10^(-3) \,\ mol/L }`

2. Determine Concentration of Unionized Ethanoic Acid

Unionized ethanoic acid does not dissociate into H+ ions. Therefore, its concentration is the same as concentration of ethanoic acid, which is 0.100 mol/L.

3. Calculate Total Concentration

Now, we calculate the total concentration, which includes both ethanoic acid and ethanoate ions:

`\boxed{\texttt{Total concentration = Concentration of ethanoic acid + Concentration of H+}}`

• 
  `\tt{Total\ concentration = 0.100\ mol/L + 1.09647819 * 10^(-3) \ mol/L}`

• 
  `\tt{Total\ concentration = 0.10109647819\ mol/L}`

4. Find Percentage of Unionized Ethanoic Acid

To find the percentage of unionized ethanoic acid, we divide the concentration of ethanoic acid by the total concentration and multiply by 100:

`\boxed{\texttt{Percentage of unionized ethanoic acid = $\frac{\texttt{Concentration of ethanoic acid}}{\texttt{Total concentration}}$ $*$ 100}}`

• 
  `\tt{Percentage = (0.100\ mol/L)/(0.10109647819\ mol/L) * 100\%}`

• 
  `\tt{Percentage = 0.98915414058 %}`

5. Final Answer

The percentage of the total ethanoic acid and ethanoate concentration that consists of unionized ethanoic acid is approximately 98.9%, which is option A.

#BTH1

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