Respuesta :
Answer: The pH of the solution is 3.03
Explanation:
We are given:
Concentration of acid = 2.1 mg/mL
Converting this into mol/L, we use the conversion factor:
1 g = 1000 mg
1 L = 1000 mL
Molar mass of ascorbic acid = 176.12 g/mol
Converting the concentration, we get:
[tex]\Rightarrow (\frac{2.1mg}{1mL})\times (\frac{1000mL}{1L})\times (\frac{1g}{1000mg})\times (\frac{1mol}{176.12g})=0.0119mol/L[/tex]
The chemical equation for the first dissociation of oxalic acid follows:
[tex]H_2C_6H_6O_6(aq.)\rightleftharpoons H^+(aq.)+HC_6H_6O_6^-(aq.)[/tex]
Initial: 0.0119
At eqllm: 0.0119-x x x
The expression of first equilibrium constant equation follows:
[tex]Ka_1=\frac{[H^+][HC_6H_6O_6^{-}]}{[H_2C_6H_6O_6]}[/tex]
We know that:
[tex]Ka_1\text{ for }H_2C_6H_6O_6=7.9\times 10^{-5}[/tex]
Putting values in above equation, we get:
[tex]7.9\times 10^{-5}=\frac{x\times x}{(0.0119-x)}\\\\x=-0.001,0.00093[/tex]
Neglecting the negative value of 'x', because concentration cannot be negative.
To calculate the pH of the solution, we use the equation:
[tex]pH=-\log[H^+][/tex]
We are given:
[tex][H^+]=0.00093M[/tex]
Putting values in above equation, we get:
[tex]pH=-\log(0.00093)\\\\pH=3.03[/tex]
Hence, the pH of the solution is 3.03
