Question

problem 7 of 37
answer:
a fe₂s₃(s) + hcl(g) → fecl₃(s) + h₂s(g)
b fe₂(so₄)₃(s) + hcl(g) → 2fecl₃(s) + 3h₂s(g)
c fe₂s₃(s) + 6hcl(g) → 2fecl₃(s) + 3h₂s(g)
d fe₂s₃(s) + hcl(g) → fe₃cl(s) + h₂s(g)

Explanation:

Step1: Check the chemical formula

• For option B, the reactant has sulfate ($\text{SO}_4$) which is not in the correct reaction context as the other options have sulfide ($\text{S}$ related in a different way). So B is wrong.
• For option D, $\text{Fe}_3\text{Cl}$ is an incorrect chemical formula. Iron(III) chloride should be $\text{FeCl}_3$. So D is wrong.

Step2: Balance the equation

• For option A:
• Left - hand side: 2 Fe, 3 S, 1 H, 1 Cl.
• Right - hand side: 1 Fe, 1 S, 2 H, 3 Cl. Not balanced.
• For option C:
• Left - hand side: 2 Fe ($\text{Fe}_2\text{S}_3$), 3 S ($\text{Fe}_2\text{S}_3$), 6 H (6$\text{HCl}$), 6 Cl (6$\text{HCl}$).
• Right - hand side: 2 Fe (2$\text{FeCl}_3$), 3 S (3$\text{H}_2\text{S}$), 6 H (3$\text{H}_2\text{S}$), 6 Cl (2$\text{FeCl}_3$). Balanced.

Answer:

C. $\text{Fe}_2\text{S}_3(\text{s})+6\text{HCl}(\text{g})\to2\text{FeCl}_3(\text{s}) + 3\text{H}_2\text{S}(\text{g})$