First off, we need to write out the balanced chemical equation for this reaction (include states too!),
2NaOH(aq) + H2SO4(aq) --> Na2SO4(aq) + 2H2O(l)
We are given that NaOH is 210g
Figure out the moles,
n=m/M
=210 / 2(22.99) + 2(16) + 2(1.008)
=2.625...
Now look back at the chemical equation, the mole ratio from NaOH and Na2SO4 is 2:1
So divide the moles of NaOH by 2 to get the moles of Na2SO4
You get, n=1.312...
Use n=m/M again to find the mass of Na2SO4
1.312.. = m / 2(22.99) + 32.06 + 4(16)
m = 1.312.. x (2(22.99) + 32.06 + 4(16))
= 186.4g (1 d.p)
Therefore, mass of Na2SO4 (sodium sulfate) is 186.4g
HOPE THIS HELPED!
