Question

Calculate the pH of a formic acid solution that contains 1.35 grams of formic acid by mass. (Assume density of the solution = 1.01 g/ml.)

Answer 1

To determine the pH of a formic acid solution, calculate the molarity from the given mass and density, then use the Ka value with an ICE table or Henderson-Hasselbalch equation to find [H+].

Step-by-step explanation:

To calculate the pH of the formic acid solution, we first need to find the molarity of the solution. Using the molar mass of formic acid (HCOOH, which is approximately 46 g/mol), we can calculate the moles of formic acid present in 1.35 grams:

1. Calculate moles of formic acid: moles = mass (g) / molar mass (g/mol) = 1.35 g / 46 g/mol = 0.02935 mol.
2. Since the density of the solution is given as 1.01 g/mL, we can assume that the weight of 1 mL of the solution is 1.01 g. To find the volume of the solution that contains 1.35 g of formic acid, we divide the mass of formic acid by the density of the solution: volume = mass / density = 1.35 g / 1.01 g/mL = 1.3366 mL.
3. Now, convert the volume from mL to L to find the molarity: 1.3366 mL = 0.0013366 L.
4. Calculate molarity (M): M = moles / L = 0.02935 mol / 0.0013366 L = 21.95 M.

To find the pH of the solution, we can use the formula pH = -log[H+], where [H+] is the concentration of hydrogen ions in the solution. Since formic acid is a weak acid, it does not fully dissociate in water. We can use its acid dissociation constant, Ka, and apply the Henderson-Hasselbalch equation or an appropriate ICE table (Initial, Change, Equilibrium) to find the concentration of hydrogen ions.

Without the Ka value provided, we cannot complete this calculation; however, if we were provided with it or could look it up, we would proceed with the ICE table method to calculate the pH of such a concentrated solution accurately.