# Buffers

## Background

As 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 of resistingchanges in pH when acid or base is added.

Before I move on I suggest you read the pdf documents showing how equilibriums are calculated and howpH in a NaHCO3 solution is calculated. Links are found in the margin to the left. Also notice that this webpagealso has its own pdf version.

## NaHCO3 considered

Consider the solution mentioned in the NaHCO3 section made up of 0.1 M NaHCO3.We can show that unlikepure water this solution of sodium bicarbonate is extremely good at resisting pH changes when HCl is added.

As is seen in this excel spreadsheet at the end of row 16, the pH in the solution is 8.31. Now let's figure outwhat happens when 0.0005 mole HCl is added (volume change is neglected).

This starts at row 20 in the excel document. In row 29it is seen that the pH should decrease to approximately pH = 8.21 which is not much.

Had it been a solution ofpure water the pH would have dropped to -LOG10(0.0005) = 3.3.

## Web resources

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...

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 ...

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 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...