This site is about five different inorganic chemistry subjects related to pH.

Basic concepts - the pH scale

pH can be measured by a hydrogen sensitive electrode or a pH meter. pH is defined as the negative base 10 logarithm of the hydrogen ion activity{H+}, and not the hydrogen ion concentration [H+]:

pH = -Log10{H+}

Topic: Ideal Gas Law
The pH scale
Ionic Strength
The pH scale

There's a consensus among chemistry teachers that students should be taught that pH = -Log10[H+] until they reach universitylevel where they are told (at least at chemistry departments) the truth that pH = -Log10{H+}.

If you read this and have been told that pH = -Log10[H+] please keep on reading. You will still be able to learn from the informationprovided here at pH scale.

In the section about ionic strength there are examples and discussion about how [H+] is calculated from {H+} and why it is importantto be able to do so in some situations.


Topic: Equilibriums
The pH scale
The pH scale
The pH scale

The pH scale

The range of the pH scale is from 0 to 14. The pH of a 1 mol/L HCl is solution is approximately 0 (because of ionic interactions between H2O,H+ and Cl-, the pH is not exactly 0 - see the ionic strength section). Any solution with a pH less than 7 is by definitionacidic.

Alkaline or basic solutions are those with a pH above 7. while neutral solutions have a pH of exactly 7.

Below is a picture of a scale showing pH from 0 to 14 with examples of solutions with different pH levels:

The pH scale
Topic: pKa & Ka
The pH scale
The basics
The pH scale

Figure: The pH values of the shown solutions are approximate. E.g. the pH of seawater is usually from 7.5 to 8.4.

There are much more than discussions about the pH scale at this webpage, so please take your time to read or download the pdf files or read the webpages.

Contact

Web resources

John Kyrk - it is essential to be a bit interactive here
General Chemistry Resources

PDF library

PDF library Note: Discussions about the pdf documents are found in the 'Help & Discussions' section. Inorganic chemistry subjects: Equilibriums 1 : A tutorial about how [CO2], [HCO3-] and[CO32-] are calculated from Total Inorganic Carbon.The pdf is here Ionic Strength 1 : An introduction about Ionic Strength with a simple calculation using H+...

Buffers

Buffers BackgroundAs shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3 abuffer has the capability of keeping pH within a certain and narrow range even if an excessof hydrogen ions H+ or hydroxide ions OH- are added.In this particular page I will elaborate a bit on why buffers actually have the capabilities ...

Ions and compounds

Ions and compounds Atoms are made up of neutrons that are neutral and have no charge, protons with a positive charge andelectrons with a negative charge.An ion is an entity or a group of atoms with a positive or negative charge such as the positively charged hydrogen ion H+ and thenegatively charged nitrate ion NO3-. Negatively charged ions are also...

Questions & Answers

Questions & Answers Question about acetate buffer and what happens when HCl is added to such a solutionDebra ask:How do I attack this problem?I want to compare the effect of adding 1mmol of HCL to 100 ml of 0.2M acetate buffer at two different starting pH's. (pKa of acetate buffer =4.7Initial pH = 4.7Initial pH = 5.7Thank youHi Debra,There is bo...

pH strips

pH strips Background Substances with the property to change color when they come into contact with an either acidic or basicsolution are called pH indicators. This is used in pH strips that changes color when they come into contactwith hydrogen ions (H+) and hydroxide ions (OH-). Usually, pH strips are b...

Question about acetate buffer

Question about acetate buffer This is the long and computational answer to Debra's question about what happens when 100 mmol of HCl ispoured into an 100 ml acetate buffer (0.2 M) 06.07.2019 Author: Jim ...

pH meter pH strips

pH meter pH strips Background pH meters have been used since 1936 when they were invented by the Danish company Radiometer.In contrast to many other measuring devices pH meters do not measure concentrations, rather they measure activities. Tobe more specific the pH meter does not measure the concentration of hydrogen ions. pH meters are used to ...

NaHCO3 dissolved in water - how is pH calculated?

NaHCO3 dissolved in water - how is pH calculated? Background about buffersA buffer is a solution that has the ability to keep pH within a certain and narrow range: even if an excessof hydrogen ions (H+) is applied to the solution. In other words:buffers resist changes in pH whenreasonable amount of either H+ or OH- is added to the buffer solution.Th...

pKa and Ka

pKa and Ka Background informationThe Ka value is a value used to describe the tendency of compounds or ions to dissociate. The Ka value is also called the dissociationconstant, the ionisation constant, and the acid constant.Topic: Equilibriums The pH scale The ...

 - - PHScale.net

Gases - the ideal gas law explained Chemical compounds in aqueous solutions are fairly easy to handle as their quantities can either be expressed in weight such as grams or kilos, moles perliter (molarity) or moles per kg (molality). Topic: pKa & Ka The basics ...

An introduction to Ionic Strength

An introduction to Ionic Strength Background To quantify the effect of inter-ionic interactions, such as molecular attraction and repelling, one has to have a `parameter` describing themagnitude of these forces and how they alter the way certain calculation are done. Topic: Equilibriums The pH s...

Buffers and Equilibriums

Buffers and Equilibriums As shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3, a buffer has the capability of keeping pH withina certain and narrow range even if an excess of hydrogen ions H+ or hydroxide ions OH- are added. In this particular page I will elaborate a bit on why buffers actually have the ca...

Acids and bases - Broensted-Lowry definition

Acids and bases - Broensted-Lowry definition A more fundamental definition of acids and bases than the one provided on the index page was given by the Danish chemists Johannes Broensted. The definitions are:A Broensted acid is a proton doner.A Broensted base is a proton acceptor. The English chemist, Thomas Lowry, proposed exactly the same at roug...

Buffers and Equilibriums

Buffers and Equilibriums As shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3, a buffer has the capability of keeping pH withina certain and narrow range even if an excess of hydrogen ions H+ or hydroxide ions OH- are added. In this particular page I will elaborate a bit on why buffers actually have the ca...

Buffers

Buffers BackgroundAs shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3 abuffer has the capability of keeping pH within a certain and narrow range even if an excessof hydrogen ions H+ or hydroxide ions OH- are added.In this particular page I will elaborate a bit on why buffers actually have the capabilities ...

 - - PHScale.net

Gases - the ideal gas law explained Chemical compounds in aqueous solutions are fairly easy to handle as their quantities can either be expressed in weight such as grams or kilos, moles perliter (molarity) or moles per kg (molality). Topic: pKa & Ka The basics ...

An introduction to Ionic Strength

An introduction to Ionic Strength Background To quantify the effect of inter-ionic interactions, such as molecular attraction and repelling, one has to have a `parameter` describing themagnitude of these forces and how they alter the way certain calculation are done. Topic: Equilibriums The pH s...