What is the formula of the titration curve of a monoprotic strong acid versus a monoprotic weak base?
We make use of eq1 from a previous article except that C_{b }is now the concentration of a weak base. Since the weak base is partially ionised in water, at any point of the titration, the sum of the number of moles of BOH and B^{+} must equal to the number of moles of BOH if it were undissociated. As the change in volume of the solution is common to all ions,
where V_{a} and V_{b} are the volume of strong acid in the solution and the volume of weak base in the solution respectively. Substitute in eq9 where K_{b }is the dissociation constant of BOH and rearranging, we have,
Substitute eq10, eq2, K_{w }= [H^{+}][OH^{–}] and [H^{+}] = 10^{pH} in eq1,
Eq11 is the complete pH titration curve for a monoprotic strong acid versus monoprotic weak base system. We can input it in a mathematical software to generate a curve of pH against V_{a}. For example, if we titrate 10 cm^{3} of 0.200 M of aqueous NH_{3} (K_{b }= 1.8 x 10^{5}) with 0.100 M of HCl, we have the following:
To understand the change in pH near the stoichiometric point versus the change in V_{a}, we assume that one drop of acid is about 0.05 cm^{3} and substitute 19.95 cm^{3}, 20.00 cm^{3} and 20.05 cm^{3} into eq11. The respective pH just before and just after the stoichiometric point (SP) are:

One drop before SP  SP 
One drop after SP 
Volume, cm^{3} 
19.95  20.00 
20.05 
pH 
6.65  5.22 
3.78 
The data shows that two drops of acid cause a change of 2.87 in pH before and after the stoichiometric point. Since the change in pH at the stoichiometric point is smaller than that of a strong acid versus strong base titration, we can use fewer indicators that work within the range to monitor the titration. Lastly, we can derive the gradient equation for a strong acid to weak base titration and investigate the inflexion point at pH 5.22 by differentiating eq11 implicitly (see previous article), resulting in , i.e. a gradient that makes angle of –89.52^{o} with the horizontal.