Final answer:
To find the concentration of hydronium ion and the pH in a 0.534-M solution of formic acid, we use the provided Ka value to set up an equilibrium expression and then calculate pH from the hydronium concentration.
Step-by-step explanation:
The sting of an ant contains formic acid, and when dealing with a 0.534-M solution of it, we need to determine the concentration of hydronium ion and the pH. Using the given acid dissociation constant (Ka = 1.8 × 10-4), we can set up an equilibrium expression to find the concentration of hydronium ions (H3O+) in the solution. To calculate pH, we use the formula pH = -log[H3O+]. While the exact calculations are not presented here, this is the process that would be used to find the needed concentrations, assuming you're familiar with chemical equilibrium and the use of the acid dissociation constant.