The pH of a 0.0040 M solution of HNO₃ is

Answer 1

Hey Alex!

Let's give this one a go. The formula for pH is:

pH = -log[H+]

We've been given a 0.0040 M solution of HNO3. We know that since protons (H+) make a solution more acidic, to get the concentration of protons we'll need to determine what happens when we isolate a proton from HNO3. Nitric acid (HNO3) is a strong acid, meaning it will dissociate (break into ions) once it comes in contact with water, as so:

HNO₃ + H₂O -> H⁺ + NO₃^-

This means that for every 1 mole of HNO₃ that dissociates, 1 mole of H⁺ is produced. Thus, every 0.0040M of HNO3 produces 0.0040M of H+

Perfect! Now we can plug our [H+] into the formula for pH:

pH = -log[H+]

pH = -log[0.0040M]

pH = 2.397940009

We have 2 significant figures (sig figs) in our given value 0.0040M, so our answer will have 2 sig figs as well:

pH = 2.4

Hope this helps! :)