# What is an example of buffering capacity?

##### 1 Answer

Here is an example using one of my students' data.

Suppose you want the buffer capacity after the FIRST addition of

#beta = (DeltaN)/(Delta"pH") > 0# where:

#DeltaN# is the mols of#"HCl"# (or#"NaOH"# ) added to the buffer, divided by the volume of theyou actually used (not the*buffer*#"HCl"//"NaOH"# ).#Delta"pH"# is simply the change in#"pH"# you got due to the first addition. Treat this as a positive quantity.

Let's say the

We get mols of:

#n_"HCl" = overbrace("0.15 mol HCl"/cancel"1 L")^"conc." xx [overbrace((5.23 cancel"mL" - 0.23 cancel"mL"))^"volume added via burette" xx cancel"1 L"/(1000 cancel"mL")]#

#= 7.50 xx 10^(-4) "mols HCl"#

So the numerator becomes:

#DeltaN = (7.50 xx 10^(-4) "mols HCl")/(underbrace(30.0 cancel"mL buffer soln")_"initial volume" xx "1 L"/(1000 cancel"mL")#

#=# #"0.0250 mols HCl/L buffer soln"#

And the denominator is:

#Delta"pH" = |6.15 - 6.73| = |-0.58| = "0.58 pH units"#

So, the **buffer capacity** after this *first* addition of

#color(blue)(beta) = "0.0250 mols HCl"/("L buffer soln" cdot "0.58 pH")#

#= color(blue)("0.043 mol/L"cdot"pH")#