what is the ph at 25 degrees Celsius of a solution made by dissolving a 5.00 grain tablet of aspirin in 0.500 litres of water? The tablet contains 0.325g of the acid HC9H7O4. ka=3.3*10^-4mm=180.2g/l
To find the pH of a solution made by dissolving a tablet of aspirin in water, we need to use the chemical equation for the dissociation of aspirin in water and the equilibrium constant expression.
The chemical equation for the dissociation of aspirin (HC9H7O4) in water (H2O) is as follows:
HC9H7O4 + H2O ⇌ H3O+ + C9H7O4^-
In this equation, aspirin (HC9H7O4) dissociates to form hydronium ions (H3O+) and the conjugate base of aspirin (C9H7O4^-).
The equilibrium constant expression for this reaction is given by:
Ka = [H3O+][C9H7O4^-] / [HC9H7O4]
where [H3O+], [C9H7O4^-], and [HC9H7O4] represent the concentrations of hydronium ions, the conjugate base, and the undissociated acid, respectively.
Given that the aspirin tablet contains 0.325 g of HC9H7O4, we can convert this mass to moles using its molar mass:
Molar mass of HC9H7O4 = 180.2 g/mol
moles of HC9H7O4 = (0.325 g) / (180.2 g/mol)
Next, we need to determine the concentration of the acid in the solution. Since we dissolved the tablet in 0.500 liters of water, the concentration will be:
Concentration of HC9H7O4 = moles of HC9H7O4 / volume of solution
volume of solution = 0.500 L
Now, we need to determine the concentration of the hydronium ions (H3O+). Since the stoichiometric coefficient of H3O+ in the balanced equation is 1, the concentration of H3O+ will be equal to the concentration of HC9H7O4.
Concentration of H3O+ = Concentration of HC9H7O4
Finally, we can use the equilibrium constant expression to find the concentration of the conjugate base (C9H7O4^-):
Ka = [H3O+][C9H7O4^-] / [HC9H7O4]
Rearranging the equation, we get:
[C9H7O4^-] = (Ka * [HC9H7O4]) / [H3O+]
Plug in the known values and calculate the concentration of C9H7O4^-.
From the concentration of H3O+, we can calculate the pOH using the formula:
pOH = -log[H3O+]
Finally, we can calculate the pH using the equation:
pH = 14 - pOH
Note: The value of Ka (3.3 * 10^-4) and the molar mass of HC9H7O4 (180.2 g/mol) provided in the question are insufficient to calculate the exact pH value. Additional information regarding the initial concentration of HC9H7O4 is required.