A solution is prepared by dissolving hydrocyanic acid in 2 liters of water if the H concentration was found to be equal to 0.34 moles. Calculate the pH of this hydrocyanic acid solution. All right, so remember pH is equal to the negative log of our H plus concentration. Another name for concentration is molarity.
So here we're going to say molarity equals moles over liters. We're going to take the moles of H plus ion given to us divided by the 2 liters, so that gives me 0.17 molar. We're then just going to say now pH equals the negative log of 0.17 molar here. When we work that out, that's going to give me 0.77 at the pH of this solution.
Here the numbers a little bit high because we're able to generate quite a bit of H ion for 0.17. Molar is a pretty large number. Remember when we're dealing with the pH scale from zero to 14, we can go up to one molar to fall within that range. 0.17 is pretty high up there along the way to towards one molar.
Again, we figured out the concentration of H plus ions here, plugged it into the formula, and we're able to deduce what our pH is at 0.77.