pH formula?
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Re: pH formula?
I don't think we need to know how to derive it since pH is just an invented representation of proton concentration. For acid it's (-log[H+]), for base it's 14 - (-log[OH-])
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Re: pH formula?
pH = - log[H+] while pOH is either 14 - pH or -log[OH-]. We do not need to know how these formulas were derived.
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Re: pH formula?
We don't need to know how they're derived although reading through the textbook I feel it is helpful in understanding how they work.
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Re: pH formula?
Don't forget that because pH= -log[H3O+]= -log(1.0x10-7) = -(-7)=7 for a change in 1 pH unit, the [H3O+] changes by a factor of 10.
Re: pH formula?
The acid and base concentrations of the formula add up to 14, so there may be a pH of 8, which means there is a pOH of of 6
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Re: pH formula?
The formula for pH is -log[H+] and pOH is -log[OH-]. I don't think we need to know the derivation, but it is helpful to know that pH + pOH = 14
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Re: pH formula?
You just need to know how to calculate pH and pOH from the [H+] and [OH-] given, and vice versa. pH = -log([H+]) and pOH = -log([OH-]) = 14 - pH
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Re: pH formula?
pH= -log(H+) you can also find pH from the equation 14= pOH+ pH if you were given the pOH.
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Re: pH formula?
You could find pH using pH=-log[H+]. Or, if you have the pOH, you could subtract it from 14 to find the pH.
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Re: pH formula?
Professor Lavelle mentioned that when you see 'p' in chemistry it means take the negative log. So 'pH' means to take the negative log of the species with H+, or H3O+
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Re: pH formula?
P itself just stands for -log
When you say pH it means calculating the -log [H3O+] where the brackets show the concentration of the H3O+ ion
pOH is -log[OH-]
When you say pH it means calculating the -log [H3O+] where the brackets show the concentration of the H3O+ ion
pOH is -log[OH-]
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Re: pH formula?
I don't think you need to know how it was derived but definitely know that ph=(-log([H+]) and that [H+]=10^(-pH)
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Re: pH formula?
The formula is -log[H+], basically just measuring the amount of protons in a solution, determining if it is acidic or basic.
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Re: pH formula?
Just to clarify, when using the concentration of OH to find the pH, you simply subtract -log[OH-] from 14 and that will equal the pH?
Last edited by Joshua Eidam 2A on Wed Dec 09, 2020 2:50 pm, edited 1 time in total.
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Re: pH formula?
lwong Dis1L wrote:What is the difference between pH=-log[H3O+] and pH=-log[H+]?
They are the same thing. The H3O+ just represents the H+ bonded with an H2O but the concentration of either of them can be used to find the pH.
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Re: pH formula?
Also, when trying to find the concentration of the H+ or OH- from a pH or pOH, how do you do the reverse of -log[ ]?
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Re: pH formula?
Hi! I think this would be helpful to know
pH=14.00-pOH= -log[H+]
pOH=14.00-pH= -log[OH-]
pH=14.00-pOH= -log[H+]
pOH=14.00-pH= -log[OH-]
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Re: pH formula?
Ariel Guan 1G wrote:pH = -log[H+]
[H+] = 10^(-pH)
pOH = -log[OH-]
[OH-] = 10^(-pOH)
14 = pH + pOH
This is helpful! Thank you.
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Re: pH formula?
pH formula is pH=-log[H+] and Im not sure if we need to know how it's derived, but another formula for pH is pH=14.00-pOH
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Re: pH formula?
The pH formula is -log[H+], and to derive it, you should know how to determine its relation to pKa and pOH.
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Re: pH formula?
pH formula: -log[H+]. As others have already mentioned, I don't think we need to know how to derive it, but it definitely wouldn't hurt to have as background knowledge.
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Re: pH formula?
As others have said, the pH formula is technically pH = -log[H+]. However, we learned in class today that with strong acids, the proton concentration can be considered the same value as the hydronium ion concentration, so pH = -log[H3O+]. We can assume a base of 10 for log equations.
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Re: pH formula?
The formula that was provided in class today was -log[H+]. I do not know if we need to know anything past how to use this.
Re: pH formula?
The formula to calculate pH is -log10[H30+]. Dr Lavelle said in lecture that he will go over this more in depth later on.
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Re: pH formula?
From my past classes we were told to know that pH = - log[H+] and pOH = -log[OH-].In addition, we should know pH + pOH = 14.
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Re: pH formula?
you just use the logarithm equation he gave us in class today! make sure you use the negative though since we're taking the log of a concentration which is really small, so it would be at a negative power.
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Re: pH formula?
The pH formula is -log[H+], however, based on the material taught in lecture I don't believe we will need to know how it is derived :) hope this helped!
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Re: pH formula?
The pH formula is pH = -log[H+]. The pOH formula is pOH = -log[OH-]. These two are related by the equation 14 = pH + pOH.
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Re: pH formula?
Hi! pH = -log[H+]. A good general rule to remember is that p indicates -log. So pOH would be -log[OH-]. It's simply an easier way to indicate acidity instead of writing out the number in scientific notation.
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Re: pH formula?
I don't think we need to know how to derive the formula, but we should know that pH = -log[H+]. [H+] means the concentration of hydrogen ions, and when you add the pH and pOH they should add to 14.
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Re: pH formula?
pH = -log[H+] and this is used because we don't want to always write out the concentration of H+, as pH is easier to write
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Re: pH formula?
Hi,
The pH formula is pH = - log [H+] or pOH = - log [OH-]. When the [H+] is given, use the first formula to solve for pH and when the [OH-] is given, use the second formula to solve for pOH and 14 - pOH = pH.
The pH formula is pH = - log [H+] or pOH = - log [OH-]. When the [H+] is given, use the first formula to solve for pH and when the [OH-] is given, use the second formula to solve for pOH and 14 - pOH = pH.
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