Final answer:
There are a total of 4 molecules with the chemical formula BH₂Cl.
Step-by-step explanation:
Starting with BCl₃ and replacing two chlorines by hydrogens to give BH₂Cl, there are a total of 4 molecules with this chemical formula. In BH₂Cl, there are two hydrogen atoms and one chlorine atom.
Since we replaced two chlorines, there are two possibilities for the location of the chlorine atom, resulting in two different molecules: BH₂Cl and H₂BCl. Additionally, each of these two molecules can exist in two different orientations, resulting in a total of four molecules: BH₂Cl, ClBH₂, H₂BCl, and ClBH₂.