nacl + h2so4 > na2so4 + hcl
balance the double replacement chemical reaction.

The balanced equation is:

2 NaCl + H₂SO₄ ---> Na₂SO₄ + 2 HCl

Explanation:

For balance the chemical equation, you must first look at the subscripts next to each atom to find the number of atoms in the equation. If the same atom appears in more than one molecule, you must add its amounts

Left side: 1 sodium Na, 1  chlorine Cl, 2 hydrogen, 1 sulfur S and 4 oxygen.

Right side: 2 sodium Na, 1  chlorine Cl, 1 hydrogen, 1 sulfur S and 4 oxygen.

The coefficients of each molecule below indicate the amount of each molecule for the reaction. This coefficient can be modified to balance the equation, just as you should never alter the subscripts.

By multiplying the coefficient mentioned by the subscript, you get the amount of each element present in the reaction. So,  in this case, since all the coefficients are 1, the quantity of each element on each side of the reaction is maintained.

Since the amount of sodium Na is different on each side of the reaction, the equation will be balanced as follows:

2 NaCl + H₂SO₄ ---> Na₂SO₄ + HCl

Now you have:

Left side: 2*1=2 sodium Na, 2*1=2  chlorine Cl, 2 hydrogen, 1 sulfur S and 4 oxygen.

Right side: 2 sodium Na, 1  chlorine Cl, 1 hydrogen, 1 sulfur S and 4 oxygen.

Since the amount of chlorine Cl is different on each side of the reaction, the equation will be balanced as follows:

2 NaCl + H₂SO₄ ---> Na₂SO₄ + 2 HCl

Now you have:

Left side: 2*1=2 sodium Na, 2*1=2  chlorine Cl, 2 hydrogen, 1 sulfur S and 4 oxygen.

Right side: 2 sodium Na, 2*1=2  chlorine Cl, 2*1=2 hydrogen, 1 sulfur S and 4 oxygen.

Note that you finally get the same amount of each element on each side of the reaction. So the balanced equation is:

2 NaCl + H₂SO₄ ---> Na₂SO₄ + 2 HCl