Question

Calculate the pH of a 0.313 M aqueous solution of acetic acid (CH3COOH, KA = 1.8x105) pH Calculate the pH of a 0.0267 M aqueous solution of acetylsalicylic acid (aspirin) (HC,H,O4K, 3.0x104) pH

Answer 1

The pH of a 0.313 M aqueous solution of acetic acid is 2.88 and the pH of a 0.0267 M aqueous solution of acetylsalicylic acid is 4.16

Step-by-step explanation:

The pH of a solution can be calculated using the equation pH = -log[H+]. In the case of acetic acid, the initial concentration is given as 0.313 M. The Ka value for acetic acid is 1.8x10^-5. Using this information, we can calculate the pH as follows:

pH = -log([H+]) = -log(√(Ka x [acid])) = -log(√(1.8x10^-5 x 0.313)) = 2.88

Similarly, for acetylsalicylic acid, the initial concentration is given as 0.0267 M and the Ka value is 3.0x10^4. Using the same equation, we can calculate the pH as:

pH = -log([H+]) = -log(√(Ka x [acid])) = -log(√(3.0x10^4 x 0.0267)) = 4.16

Answer 2

To calculate the pH of acetic acid or acetylsalicylic acid solutions, use the ICE table method to find [H+] at equilibrium and then apply the pH formula. Assumptions can simplify calculations, but may require solving a quadratic equation if invalid.

Step-by-step explanation:

To calculate the pH of a 0.313 M aqueous solution of acetic acid (CH3COOH) with a Ka of 1.8 x 10-5, first determine the concentration of hydrogen ions [H+] at equilibrium using the ICE table approach and the formula:

[H+] = √(Ka × [acid Initial])

Once [H+] is calculated, use the equation pH = -log[H+] to find the pH. Typically, some assumptions are made such that the initial concentration of acetic acid does not change significantly upon dissociation, meaning the change in concentration 'x' of H+ is small relative to the initial concentration of the acid.

Next, to calculate the pH of a 0.0267 M aqueous solution of acetylsalicylic acid (aspirin) with a Ka of 3.0 x 10-4, follow the same ICE table method and assumptions.

For both of these calculations, once [H+] is known, apply the formula for pH. If needed, solve quadratic equations when assumptions about 'x' being small are not valid.