Respuesta :
Answer: The pH of given solution is 3.74.
Explanation:
The given data is as follows.
Mass of lactic acid = 8.52 g, Formula weight of lactic acid = 90.08 g/mol
So, number of moles of lactic acid will be calculated as follows.
No. of moles = [tex]\frac{mass}{\text{molar mass}}[/tex]
= [tex]\frac{8.52 g}{90.08 g/mol}[/tex]
= 0.094 moles
Mass of sodium lactate = 7.93 g, Formula weight of sodium lactate = 112.06 g/mol
Hence, number of moles of sodium lactate is as follows.
No. of moles = [tex]\frac{mass}{\text{molar mass}}[/tex]
= [tex]\frac{7.93 g}{112.06 g/mol}[/tex]
= 0.071 moles
As we know that relation between [tex]K_{a}[/tex] and [tex]pK_{a}[/tex] is as follows.
[tex]pK_{a} = -log K_{a}[/tex]
= -log(0.000137)
= 3.86
Using Henderson equation, we will calculate the pH as follows.
pH = [tex]pK_{a} + log (\frac{\text{Conjugate base}}{\text{Acid}})[/tex]
pH = [tex]3.86 + log (\frac{\text{sodium lactate}}{\text{lactic acid}})[/tex]
= [tex]3.86 + log (\frac{0.071}{0.094})[/tex]
= 3.86 + log (0.755)
= 3.86 - 0.121
= 3.74
Therefore, we can conclude that pH of given solution is 3.74.
