What is the total number of buffers formed during the titration of $H_3PO_4$ with $NaOH$?

When a person breathes rapidly during fear or excitement,the concentration of $CO_2$ in the blood decreases. What happens to the $pH$ of the blood?

If $20 \ mL$ of $0.1 \ M \ NaOH$ is added to $30 \ mL$ of $0.2 \ M \ CH_3COOH$ $(pK_a = 4.74)$,the $pH$ of the resulting solution is

Calculate the $pH$ of a buffer solution containing $0.01 \ M$ salt and $0.004 \ M$ weak acid. $(pK_{a} = 4.762)$

$0.1 \ M$ $CH_3COOH$ is titrated against $0.1 \ M$ $NaOH$. What would be the difference in $pH$ between $1/4$ and $3/4$ stages of neutralization of the acid?

Which of the following solutions does not act as a buffer $:-$