Balance the chemical reaction in a single step. $\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

The skeletal chemical equation: $\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Step 1: For balancing a chemical equation the number of elements should have to be equal on both the sides of the reaction. So basically, the number of elements on the ($\mathrm{LHS}$) should have to be equal to the elements on the ($\mathrm{RHS}$)

Elements	Reactant side	Product size
Sodium	1	2
Oxygen	5	5
Hydrogen	3	2
Sulphur	1	1

So Sodium and Hydrogen present on both the sides are not equal.

Step 2: So for balancing the chemical equation and making the number of elements equal on both the sides, multiply Sodium hydroxide and water molecule with 2.

Elements	Reactant side	Product size
Sodium	2	2
Oxygen	5	5
Hydrogen	4	4
Sulphur	1	1

Therefore, the reaction is: $2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$