The compounds of interest are Na2S and H2SO4. The molecular equation then is: Na2S + H2SO4 ---> Na2SO4 + H2S. Just exchange one anion for the other. Now, we need to know a little bit about the properties of these compounds. Almost all sodium salts are soluble, so both Na2S and Na2SO4 are fully dissociated: 2 Na+ + S2- + 2 H+ + SO42- ---> 2 Na+ + SO42- + H2S. Crossing out terms that appear on both sides, we obtain the net ionic equation: 2 H+ + S2- ----> H2S. Conveniently, H2S is a gas, and escapes from solution. Thus, it selectively removes H+ and S2- ions from the equilibrium, driving the reaction to completion (favoring Na2SO4) Solution The compounds of interest are Na2S and H2SO4. The molecular equation then is: Na2S + H2SO4 ---> Na2SO4 + H2S. Just exchange one anion for the other. Now, we need to know a little bit about the properties of these compounds. Almost all sodium salts are soluble, so both Na2S and Na2SO4 are fully dissociated: 2 Na+ + S2- + 2 H+ + SO42- ---> 2 Na+ + SO42- + H2S. Crossing out terms that appear on both sides, we obtain the net ionic equation: 2 H+ + S2- ----> H2S. Conveniently, H2S is a gas, and escapes from solution. Thus, it selectively removes H+ and S2- ions from the equilibrium, driving the reaction to completion (favoring Na2SO4).