Chemistry

Oxidation States and Oxides

334 Questions

Oxidation states represent the degree of oxidation of an atom in a chemical compound. This topic covers calculating valency, classifying oxides as acidic or basic, and understanding thermal decomposition. These concepts are frequently tested in chemistry sections across multiple competitive examination platforms.

calculating oxidation statesclassification of oxidesvalency determinationthermal decompositionstability of metal oxides

Oxidation States and Oxides Questions

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Which of the following are basic oxides? 
$Mn _2O _7$ ,$V _2O _3$, $V _2O _5$, $Cr _2O _3, CrO$ 

  1. $Mn _2O _7$ and $V _2O _3$
  2. $V _2O _3$ and $CrO$
  3. $CrO$ and $Cr _2O _3$
  4. $V _2O _5$ and $V _2O _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As metallic character decreases as we move across the period then basicity of oxides increases.

Also, we know oxide in lowest oxidation state of element is more basic. So, in $V _2O _3$ and $CrO$, oxidation state of $V$ and $Cr$ are $+3$ and $+2$ respectively which is lowest among others.

Multiple choice chemistry p-block elements oxides of elements simple oxides oxygen

A group of acidic oxide is:

  1. $CrO _{3},Mn _{2}O _{7}$
  2. $ZnO,Al _{2}O _{3}$
  3. $CaO,ZnO$
  4. $Na _{2}O,Al _{2}O _{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

here,${ CrO } _{ 3 }$ are acidic oxides

${ CrO } _{ 3 }+{ H } _{ 2 }O\longrightarrow { H } _{ 2 }{ CrO } _{ 4 }\ { Mn } _{ 2 }{ O } _{ 7 }+{ H } _{ 2 }O\longrightarrow { 2HMnO } _{ 4 }$

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Non-metals combine with oxygen to form usually:

  1. basic oxides

  2. neutral oxides

  3. acidic oxides

  4. amphoteric oxides
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

non-metal oxides forms acid after diluting in water Eg. $\mathrm{H} _{2}C{O} _{3}, {H} _{2}S{O} _{4}$
$\therefore$   non metals combine with oxygen to from usually acidic oxcides because of its low electronegativity 

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Which one of the following is an amphoteric
oxide?

  1. $Na _{2}O$
  2. $SO _{2}$
  3. $B _{2}O _{3}$
  4. $\mathrm{Z}\mathrm{n}\mathrm{O}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation


$\mathrm Na _{2}O $ and first group oxides are basic while non-metal oxides such as $\mathrm SO _{2}$ and $B _{2}O _{3} $ are acidic.
ZnO is amphoteric because it can reacts with acid as well as base to produce salt and $\mathrm H _{2}O$.

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Which of the following is not a normal oxide?

  1. $\mathrm{N}\mathrm{a} _{2}\mathrm{O}$
  2. $\mathrm{Al} _{2}\mathrm{O} _{3}$
  3. $\mathrm{K}\mathrm{O} _{2}$
  4. $\ \mathrm{M}\mathrm{g}\mathrm{O}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$KO _2 \rightarrow K^+ O _2^-$
Hence, $KO _2$ is a super oxide with $O _2^-$ ion.
$Na _2O, Al _2O _3, M _gO$ are normal oxides with $O^{2-}$ ion.

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Metal oxide which show basic as well as acidic behaviour are known as:

  1. neutral oxide

  2. amphoteric oxide

  3. metalloid oxide

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Metal oxides which shows basic as well as acidic behaviour as known as amphoteric oxides. Thus aluminium metal and zinc metal form amphoteric oxides.

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Which of the following oxide is thermally least stable?

  1. $CaO$
  2. $Al _2O _3$
  3. $Fe _2O _3$
  4. $Ag _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The melting points and thermal stability of the oxides are determined by the nature of the distribution of valent electrons from the components over localized and nonlocalized ones and by the probability of the formation of stable electron configurations of transition metal and oxygen atoms. The drop in statistical weight of stable configurations and increase in proportion of nonlocalized electrons results in a drop in melting point and thermal stability of the oxides.

Calcium oxide is thermally least stable as it reacts exothermically with water producing hydroxide.
$CaO +H _2O \rightleftharpoons Ca(OH) _2$

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Match the following, regarding nature of the oxides.

Column -I Column-II
a. $N _2O$ (i) Basic
b. BaO (ii) Amphoteric
c. $As _2O _3$ (iii) Acidic
d. $Cl _2O _7$ (iv) Neutral

  1. a(ii), b(i), c(iii), d(iv)

  2. a(iv), b(i), c(iii), d(ii)

  3. a(iv), b(i), c(ii), d(iii)

  4. a(ii), b(i), c(iv), d(iii)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A) $N _2O\longrightarrow$ (iv) Neutral as it neither shows properties of a base nor acid.

(B) $BaO\longrightarrow$ (i) Basic; Metallic oxides are basic oxides.
(C) $As _2O _3\longrightarrow$ (ii) Amphoteric as it can act both as a base and an acid.
(D) $Cl _2O _7\longrightarrow$ (iii) Acidic as non-metallic oxides are acidic in nature.