Autoionization Reactions are those reactions in which ions or molecules ionizes spontaneously without adding any external reagent.
For Example,
Autoionization of water.
H₂O + H₂O ⇆ H₃O⁺ + OH⁻
Autoionization reaction of Methanol is shown below,
Answer:
0.171 grams of oxygen combined with the metal.
Explanation:

Mass of magnesium oxide produced = 0.421 g
Mass of magnesium metal used = 0.250 g
Suppose reaction completely converts the magnesium into magnesium oxide.
Mass of oxygen combined with magnesium = m
0.421 g = 0.250 g + m
m = 0.421 g - 0.250 g = 0.171 g
0.171 grams of oxygen combined with the metal.
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When the balanced equation for this reaction is:
2SO3 → 2SO2 + O2 so, by using ICE table:
initial 0.391 0 0.125m
change -X +2X +X
Equ (0.391-X) 2X 0.125+X
when Keq = concentration of products / concentration of reactants
so, by substitution
4.34 = [2X]^2 * [0.125+X] / [0.391-X]^2 by solving for X
∴ X = 0.357 m
∴ the concentration of SO2 = 2x = 2 * 0.357
= 0.714 m