Hidruros metálicos (Parte 2)

Summary

The video explains how to write, balance, and name two iron hydrides. In metallic hydrides, hydrogen has an oxidation number of −1. Iron can have oxidation numbers of +2 or +3, so the chosen oxidation state determines the compound’s formula.

Iron(II) hydride

• Combine iron with hydrogen using iron’s +2 oxidation state.
• Cross the oxidation-number magnitudes to form the formula FeH₂.
• Check neutrality: one Fe at +2 and two H atoms at −1 give a total of +2 − 2 = 0.
• The equation is already balanced: Fe + H₂ → FeH₂.

Names given by the usual systems:

• Traditional: ferrous hydride
• Systematic: iron dihydride
• Stock: iron hydride (II)

Iron(III) hydride

• Use iron’s +3 oxidation state. Crossing the oxidation-number magnitudes gives FeH₃.
• Balance the equation by making the hydrogen counts equal. The least common multiple of 2 and 3 is 6.
• The balanced equation is 2Fe + 3H₂ → 2FeH₃.
• The instructor leaves the naming of this compound as an exercise for students.

General lessons

• Write the metal before hydrogen in the formula.
• In a neutral compound, the oxidation numbers of all atoms, counted according to how many are present, must sum to zero.
• When balancing, adjust coefficients in front of formulas; do not change the subscripts that define the compound.
• In traditional nomenclature, the lower of two oxidation states generally takes the suffix -ous, and the higher takes -ic. For iron, these are ferrous and ferric.

The instructor ends by previewing a future lesson on nonmetallic hydrides.

Speaker and source

Axel is the instructor and sole speaker heard in the subtitles.