Which buffer is present in human blood :-

Which of the following mixtures forms an acidic buffer?

To obtain a buffer which should be suitable for maintaining a $pH$ of about $4 - 5$,we need to have in solution,a mixture of

Which of the following mixtures is called an acidic buffer?

The ratio of volumes of $CH_3COOH$ $0.1 \ N$ to $CH_3COONa$ $0.1 \ N$ required to prepare a buffer solution of $pH$ $5.74$ is (Given, $pK_a$ of $CH_3COOH$ is $4.74$)

$A$ buffer solution has equal volumes of $0.2 \ M \ NH_4OH$ and $0.02 \ M \ NH_4Cl$. The $pK_b$ of the base is $5$. The $pH$ is