What is the pH of a one liter auqueous solution to which has been added 0.2 moles of acetic acid (CH3COOH)?
CH3COOH + H2O = CH3COO- + H3O+
Acid acetic is a weak acid so not all of it will dissociate. The constant for acid acetic is 1.8 . 10^-5
therefore 1.8x10^-5=(x^2)/(0.2-x)
x is the amount that disociated
solve the equation and x is 1.88x10^-3
pH=-log(pH)=-log(1.88x10^-3)=2.72
thank you so very much this helped so much!!!!!
To find the pH of the aqueous solution containing 0.2 moles of acetic acid (CH3COOH) in one liter, you need to know the dissociation constant (Ka) of acetic acid.
The dissociation of acetic acid in water can be represented by the equation: CH3COOH ⇌ CH3COO- + H+
The dissociation constant (Ka) for acetic acid is 1.8 x 10^-5 mol/L.
To find the concentration of the acetic acid (CH3COOH) in the solution, divide the number of moles (0.2) by the volume of the solution (1 L).
Concentration (C) = Number of moles (n) / Volume (V)
C = 0.2 mol / 1 L
C = 0.2 mol/L
The concentration of the acetic acid is 0.2 mol/L.
Since acetic acid is a weak acid, we can assume that its dissociation is incomplete.
To calculate the concentration of H+ ions (protons) in the solution, we need to consider the dissociation of acetic acid.
Let x be the concentration of H+ ions (protons) and CH3COO- ions that are formed when acetic acid dissociates.
The concentration of acetic acid (CH3COOH) = initial concentration - x
The concentration of CH3COO- = x
The concentration of H+ ions = x
Since the dissociation constant (Ka) is given by the equation: Ka = [CH3COO-][H+] / [CH3COOH], we can plug in the values:
Ka = (x)(x) / (0.2 - x)
Solve for x using the quadratic equation formula: x = (-b ± √(b^2 - 4ac)) / (2a)
where a = 1, b = -Ka, c = -Ka(0.2)
Plug in the values and solve for x.
Once you have the value of x, that will represent the concentration of H+ ions (protons) in the solution.
Finally, to calculate the pH, take the negative logarithm (base 10) of the concentration of H+ ions.
pH = -log[H+]
Plug in the value of [H+] and calculate the pH.
Note: This calculation involves solving a quadratic equation, so it might be easier to use a numerical approach such as using a calculator or software to find the value of x and then calculating the pH.