6 Questions
Which metal does not form MO oxides?
Scandium
Which metal oxide has the highest oxidation number among Sc_{2}O_{3}, Mn_{2}O_{7}, Fe₂O, and V_{2}O_{5}?
Mn_{2}O_{7}
Which of the following metals exhibits a covalent green oxide?
Manganese
Which metal oxide is mainly acidic and gives HMnO upon reaction?
Manganese
Which metal's oxide is described as amphoteric but mainly acidic?
Vanadium
Which chromium compound is basic, according to the text?
CrO
Study Notes
Oxides and Oxoanions of Metals
- Metals, except scandium, form MO oxides, which are ionic, through reaction with oxygen at high temperatures.
- The highest oxidation number in the oxides coincides with the group number and is attained in Sc₂O₃ to Mn₂O₇.
- Beyond group 7, no higher oxides of iron above Fe₂O₃ are known.
Properties of Higher Oxides
- As the oxidation number of a metal increases, its ionic character decreases.
- Higher oxides, such as Mn₂O₇, CrO₃, and V₂O₅, have low melting points.
- These higher oxides exhibit acidic character, with Mn₂O₇ giving HMnO₄, and CrO₃ giving H₂CrO₄ and H₂Cr₂O₇.
- V₂O₅ is amphoteric, giving VO₄³⁻ and VO₂⁺ salts.
Vanadium Oxides
- V₂O₃ is basic, while V₂O₄ is less basic, and V₂O₅ is amphoteric.
- V₂O₄ dissolves in acids to give VO²⁺ salts.
- V₂O₅ reacts with alkalies to give VO₄³⁻ and with acids to give VO₂⁺ ions.
Chromium Oxides
- CrO is basic, while Cr₂O₃ is amphoteric.
- Potassium dichromate (K₂Cr₂O₇) is a significant chemical used in the leather industry and as an oxidant for preparing azo compounds.
This quiz covers the formation of oxides and oxoanions of metals, including the relationship between oxidation numbers and group numbers. It also includes information on the stability of oxocations.
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