# Homework Help: Calculating pH from pKw

1. Apr 10, 2016

### NihalRi

1. The problem statement, all variables and given/known data
pKw for water at 10 deg Celsius is 14.54. What is the pH of pure water at this temperature?

2. Relevant equations
kHw = [H+][OH-]

3. The attempt at a solution
I don't even know where to start on this one

2. Apr 10, 2016

### drvrm

one can start with definitions like pKw ,pH etc go to the text books or Google it

3. Apr 10, 2016

### epenguin

You could write the equation for the dissociation of water, and then ask what would be the relation between [H+] and [OH-].

It would be best to work this out yourself, perhaps the above will remind you of stuff you already studied. If not, go back to probably about the first section about pH in your textbook.

4. Apr 11, 2016

### NihalRi

[H+]^2 = 10^-14.54
SQUARE ROOTING AND THE TAKING THE MINUS OF THE LOG
pH=7.27

5. Apr 11, 2016

### drvrm

perhaps you have taken H and OH ion concentration equal-why so?

The acid potential of aqueous solutions is measured in terms of the pH scale.
The symbol "p" means take the negative logarithm of whatever follows in the formula. for pH, pOH, p[anything] .

The pH scale is a logarithmic scale.
Every multiple of ten in H ion concentration equals one unit on the logarithm scale.
Physically the pH is intended to tell what the acid "potential" is for a solution.

In a sense the system is INVERTED so a low pH value indicates a great acid potential
while a high pH indicates a low acid potential. ( Sad but true this is upside down and counter intuitive.)
The pH values range from negative values to number above 14. Commonly the scale is often misrepresented as ranging from 0 to 14. We will find that negative values are possible.

6. Apr 11, 2016

### epenguin

Looks OK to me.