Determine the pH of a 0,050M solution of lactic acid, CH3CH(OH)COOH (ka = 1.4x10^-4) and delta Grxn^o at 25 degrees C.
Determine pH and delta Grxn^o at 25 degrees C
I'm having trouble on getting started.
Let's call lactic acid HL.
.......HL --> H^+ + L^-
I.....0.05....0.....0
C.....-x......x.....x
E.....0.05-x..x.....x
Substitute the E line into Ka expression and solve for x = (H^+), then convert to pH.
dG = -RTlnKa
To determine the pH of a solution of lactic acid and the standard Gibbs free energy change (ΔGrxn°) at 25°C, we need to consider the dissociation of lactic acid in water and utilize the acid dissociation constant (Ka) value provided.
Let's first determine the pKa of lactic acid:
pKa = -log10(Ka)
Given Ka = 1.4 x 10^-4
pKa = -log10(1.4 x 10^-4)
Calculating this pKa value will give us insight into the extent of the dissociation of lactic acid in water and will help to determine the pH of the solution.
Next, we can use the Henderson-Hasselbalch equation to calculate the pH of the lactic acid solution:
pH = pKa + log10([A-]/[HA])
In this equation, [A-] represents the concentration of the conjugate base (lactate ion) and [HA] represents the concentration of the undissociated acid (lactic acid). Since we are given the concentration of the lactic acid solution (0.050 M), we can assume that the concentration of the dissociated lactate ion will be negligible compared to the undissociated acid concentration.
Finally, to determine the standard Gibbs free energy change (ΔGrxn°) at 25°C, we can use the equation:
ΔGrxn° = -RTln(Ka)
In this equation, R is the ideal gas constant (8.314 J/mol·K), T is the temperature in Kelvin (25 + 273.15), and ln denotes the natural logarithm. By plugging in the provided Ka value, we can calculate ΔGrxn°.
Following these steps, we can obtain the pH of the lactic acid solution and ΔGrxn°.