Question

An aqueous solution at 25°C is 13.9% HNO3 by mass and has a density of 1.044 g/mL. What is the pH of the solution? Option 1) pH = 0.78 Option 2) pH = 1.12 Option 3) pH = 1.29 Option 4) pH = 1.47

Answer 1

To find the pH of the solution, calculate the molarity of HNO3 and then find the negative logarithm of the molarity. The correct pH is Option 1) pH = 0.78.

Step-by-step explanation:

To find the pH of the solution, we first need to determine the concentration of HNO3 in the solution. We can do this by calculating the mass of HNO3 in the solution. Assuming we have 100 g of the solution, the mass of HNO3 would be 13.9 g (13.9% of 100 g).

Next, we can calculate the molarity of the solution using the formula:

Molarity (M) = Moles of solute / Volume of solution (L)

Assuming the density of the solution is equal to its molarity, we can use the density (1.044 g/mL) to convert the volume of solution into grams (1 mL = 1.044 g).

Now we can calculate the molarity:

M = 13.9 g / (100 g / 1.044 g/mL) = 0.144 M

Finally, we can find the pH of the solution using the formula:

pH = -log10([H+])

Since HNO3 is a strong acid, it dissociates completely in water, so the concentration of [H+] is equal to the molarity of the solution.

pH = -log10(0.144) = 0.84

Therefore, the correct option is Option 1) pH = 0.78.