What reaction occurs when iron is pickled?

6hcl + fe₂o₃ → 2fecl₃ + 3h₂o -use the subscripts of the compounds on one side of the equation to suggest coefficients for compounds on the other side. the subscript 3 in fecl3 suggests that a coefficient of 3 should be tried before the reactant that also contains chloride, yielding: (1) 3hcl + fe2o3 fecl3 + h2o in the same manner, the subscript 2 in fe2o3suggests putting a coefficient of 2 in front of fecl3, or: (2) 3hcl + fe2o3 2fecl3+ h2o finally, the presence of 6 chloride ions in 2fecl3indicates 6 chloride ions are needed in the reactant, as in: 6hcl.