\(NaHCO _{3}\) is a salt of weak acid \(\left( H _{2} CO _{3}\right)\)nd a strong base \(( NaOH )\). It undergoes hydrolysis in water as follow:
$$
NaHCO _{3\left(a_{q}\right)} \rightarrow Na _{\left(a_{p}\right)}^{+}+ HCO _{3(\text { ap })}^{-}
$$
$$
\frac{ H _{2} O _{ cr } \rightarrow H _{(a+)}^{+}+ OH _{\text {as }}^{-}}{ NaHCO _{3(k)}+ H _{2} O \rightarrow Na _{(a+)}^{-}+ H _{2} O _{(n)}+ CO _{2(s)}+ OH _{(a)}^{-}}
$$
\(OH _{(\dot{\alpha})}^{-}\)makes the solution alkaline \(NaHSO _{4}\) is a salt of strong acid \(\left( H _{2} SO _{4}\right)\) and a strong base \(( NaOH )\) which does not hydrolyse in water. And since the salt is an acidic one, its solution is acidic.
\(NaCl\) is a neutral salt of strong acid \(( HCl )\) and strong base \(( NaOH )\) and as a result does not undergo hydrolysis in water. So, its solution is neutral.
Note: Only salt of weak acid vs strong base \& strong acid vs weak base undergo hydrolysis in water to give an acidic or neutral solution.