Given the unbalanced equation: __fe2o3 + __co → __fe + __co2when the equation is correctly balanced using the smallest whole-number coefficients, what is the coefficient of co? (1) 1 (3) 3(2) 2 (4) 4

The balanced equation would be: Fe2O3+ 3CO -> 2Fe+ 3CO2.

The coefficient of CO is 3. Therefore, (3) 3 is the correct answer.

Hope this is helpful~

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.