Calculating the pH of a solution

pH.md

Hydrochloric acid

What the heck is "20° Baume muriatic acid"? Google to the rescue

It means that 100g of solution contains 31.45g HCl

Your HCl is very near to 10 mol/l or 36.5g/100ml

Strong acids dissociate completely, so pH is just the -log of the concentration (in moles/liter, called the molarity or M)

pH = -log₁₀(M)

in this case,

pH = -log₁₀(10) = -1

Wikipedia confirms.

Ammonia

Ammonia is a solution of ammonium hydroxide (NH3), which weighs 35.04 g/mole.

We have a 10% solution. Since NH3 is a gas, let's assume that's mass-percent, making it 2.85 M.

Strong bases are like strong acids except the molarity gives us the pOH

pOH = -log₁₀(2.85)

So we must find the implied H+ concentration

H+ * OH- = Kw

H+ * 2.85 = 1.0e-14
H+ = 1.0e-14 / 2.85
H+ = 3.5e-15

and then take the log of that

pH = -log₁₀(3.5e-15) = 14.5

Vinegar

Vinegar is a weak acid, so we need to consider its acid dissociation constant, Ka.

Wikipedia gives the pKa of acetic acid: 4.754. Let's convert that to Ka

Ka = 10^-pKa
Ka = 1/10^4.754 = 1.8e-5

Now we'll follow the method shown here. The H+ concentration is

H+ = sqrt(Ka/M)

Heinz white vinegar is 5% acetic acid, which is 0.83 M, so

H+ = sqrt(1.8e-5 / 0.83) = 0.0039

and the pH is

pH = -log₁₀(H+)
pH = -log₁₀(0.0039) = 2.4