Which of the following is a buffer solution?

$2 \ g$ acetic acid and $3 \ g$ sodium acetate are present in $100 \ mL$ aqueous solution. What will be the $pH$ of the solution if the ionisation constant of acetic acid is $1.8 \times 10^{-5}$?

Which statement is correct for a mixture of $1 \ M \ NaCl$ and $1 \ M \ HCl$?

$50 \, mL$ of $0.2 \, M$ ammonia solution is treated with $25 \, mL$ of $0.2 \, M$ $HCl$. If $pK_b$ of ammonia solution is $4.75$,the $pH$ of the mixture will be

$A$ solution which is resistant to change of $pH$ upon the addition of an acid or a base is known as

Which of the following mixtures forms an acidic buffer?