Hydrogen sulfide was passed through a solution containing 20 g of sodium hydroxide. Determine the mass of the salt formed?

Given:
m (NaOH) = 20 g

To find:
m (salt) -?

Decision:
1) NaOH + H2S => NaHS + H2O;
2) M (NaOH) = Mr (NaOH) = Ar (Na) * N (Na) + Ar (O) * N (O) + Ar (H) * N (H) = 23 * 1 + 16 * 1 + 1 * 1 = 40 g / mol;
M (NaHS) = Mr (NaHS) = Ar (Na) * N (Na) + Ar (H) * N (H) + Ar (S) * N (S) = 23 * 1 + 1 * 1 + 32 * 1 = 56 g / mol;
3) n (NaOH) = m (NaOH) / M (NaOH) = 20/40 = 0.5 mol;
4) n (NaHS) = n (NaOH) = 0.5 mol;
5) m (NaHS) = n (NaHS) * M (NaHS) = 0.5 * 56 = 28 g.

Answer: The mass of NaHS is 28 g.