How do I Calculate the pH of a solution containing 1L of water and 0.02 moles of hydrochloric acid?

Answer 1

The pH of a solution can be found by taking the negative log of the concentration of the Hydronium ions (H+), in terms of molarity, in the solution.
pH = -log [H+]

Molarity = moles of solute / Liters of solution
You are told that you have .02 moles of Hydrochloric acid which is dissolved in 1 Liter of water (as we assume this makes 1 Liter of solution).
moles of HCl = .02 mol
Liters of Solution = 1 L
Molarity = .02 mol / 1 L
Molarity = .02 Molar
[HCl] = .02 M
(when [ ] are used around the chemical formula, it means that we are talking about the molar concentration of the substance)


For every 1 mole of HCl which dissolves in the water, 1 mole of H+ ions are put into solution, since HCl is a strong electrolyte,
HCl (g) --H2O--> H+ (aq) + Cl- (aq)
So this means that the concentration of H+ is the same as the concentration of HCl.
[HCl] = .02 M = [H+]

pH = -log [H+]
pH = -log [.02]
pH = 1.7

So the final pH of the solution would be 1.7.

Answer 2

pH = -log [H+] so you will need to find [H+] measured in moles/L Sulfuric acid is a strong acid and will produce 2 moles H+ for every 1 mole. Potassium hydroxide is a strong base and will produce 1 mole OH- for every 1 mole. This means that there will be 0.01 moles of H+ excess after the H+ and OH- neutralize. Equation: H2SO4 + 2 KOH ----> K2SO4 + 2 H2O Calculate the molarity of this [H+] and plug into pH formula....woohoo! You just solved it!

Answer 3

you cannot answer this question correctly has you only have the moles of HCl, and not the molarity or volume, thus you cannot calculate the overall volume or concentration of the "solution", you are only given the volume of water not the overall volume

Answer 4

concentration = -log [molarity]
molarity = mol/L

molarity = 0.02mol/1L
concentration = -log [0.02M] = 1.70 pH