1. Write the balanced chemical equation:

FeS (s) + 2 HCl (aq) → FeCl₂ (aq) + H₂S (g)

2. Calculate the molar mass of hydrogen sulfide (H₂S):

* H: 1.01 g/mol (x2 = 2.02 g/mol)

* S: 32.07 g/mol

* Total: 34.09 g/mol

3. Calculate the moles of hydrogen sulfide:

* Moles = mass / molar mass

* Moles of H₂S = 12 g / 34.09 g/mol = 0.352 moles

4. Use the mole ratio from the balanced equation to find the moles of iron II sulfide (FeS):

* The equation shows a 1:1 mole ratio between FeS and H₂S.

* Therefore, 0.352 moles of FeS are needed.

5. Calculate the mass of iron II sulfide:

* Molar mass of FeS:

* Fe: 55.85 g/mol

* S: 32.07 g/mol

* Total: 87.92 g/mol

* Mass = moles x molar mass

* Mass of FeS = 0.352 moles x 87.92 g/mol = 30.9 g

Therefore, approximately 30.9 grams of iron II sulfide are needed to react with hydrochloric acid to generate 12 grams of hydrogen sulfide.