need to calculate the mass (m ) of NaoH with C% = 15 % , to balance 176 g of H2SO4 so i though to use this method C% = mass of h2s04 / mass of h2so4 + mass of Naoh which is unknown mass of Naoh = c% x mass of h2so4 / 100 is this the right method or not ?

See your post above.

Yes, the method you described is correct for calculating the mass of NaOH.

To balance a chemical equation, you need to ensure that the number of atoms of each element is the same on both sides of the equation. In this case, you want to balance the equation:

H2SO4 + NaOH -> Na2SO4 + H2O

The given information is that the mass of H2SO4 is 176 g and the percentage composition of NaOH is 15% (C% = 15%).

To find the mass of NaOH needed, you can use the formula:

mass of NaOH = C% x mass of H2SO4 / 100

Plugging in the values:

mass of NaOH = 15% x 176 g / 100 = (15/100) x 176 g = 0.15 x 176 g = 26.4 g

Therefore, the mass of NaOH required to balance 176 g of H2SO4 is 26.4 g.