If the reaction of 3.50 moles of lithium with excess hydrofluoric acid produced a 75.5% yield of hydrogen gas, what was the actual yield of hydrogen gas? unbalanced equation: li + hf lif + h2 1.32 mol h2 1.75 mol h2 2.32 mol h2 2.65 mol h2

Balanced chemical  equation  is  as  follows
2Li  +2HF  --->2  Li  +  H2
from  reaction  above  2   moles  of   Li  react  with 2  moles  of HF  to  form  2 moles of  Li  and 1  mole  of  H2
we  know the  mole of  Li  is  3.50 moles
Since  ratio  of  Li  to  H2  is  2:1  then the  mole  of  H2  is 1/2 x3.50=1.75moles

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.