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

SO2 (Sulphur dioxide) is

  1. a reducing agent

  2. an oxidising agent

  3. both reducing and oxidising agent

  4. neither an oxidising agent nor a reducing agent
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

SO2 (sulphur dioxide) can act both as a reducing and an oxidising agent.

Multiple choice

Which of the following statements is correct?

  1. H2 is paramagnetic.

  2. O2 is paramagnetic.

  3. O2 is diamagnetic.

  4. N2 is paramagnetic.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

O2 (2 electrons): (σ1s2) (σ*1s2) (σ2s2) (σ*2s2) (∏2px2≈∏2px2) (σ 2pz2) (∏2px1≈∏2px1) 2 unpaired electrons. Hence, O2 is paramagnetic.

Multiple choice

Which of the following statements is/are incorrect?

P. The central metal atom shows +4 oxidation state in potassium chromate and potassium dichromate. Q. Limonite and willemenite are ores of zinc. R. Zinc oxide is called as white lead with the formula (PbCO3)2•Pb(OH)2 and is used as a whitening material.

  1. Only P

  2. Only Q

  3. Only R

  4. P and Q

  5. Q and R
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

P. The central metal atom in potassium chromate and potassium dichromate is Cr. Chromium has +4 oxidation state in K2CrO4 and K2Cr2O7. Q. Limonite (Fe2O3.3H2O) is the ore of iron and willemite is the ore of zinc. R. Zinc oxide is an inorganic compound with the formula ZnO. ZnO is a white powder that is insoluble in water and it is widely used as an additive in numerous materials and products including rubbers, plastics, ceramics, glass, cement, etc. White lead (PbCO3)2•Pb(OH)2 is a complex chemical compound, containing both a carbonate and a hydroxide portion and occurs naturally as a mineral for lead. White lead compounds were used as pigmenting materials like cement, lubricants, etc, but due to its toxicity, it is not used frequently.

Hence, statements Q and R are incorrect.

Multiple choice

Identify the incorrect statement.

  1. Fe3+ is more stable than Fe2+.

  2. Mn2+ can be easily oxidised to Mn3+.

  3. Mn shows the greatest variation in possible oxidation numbers among 3d-series elements.

  4. The correct electronic configuration of Cr is [Ar] 3d5, 4s1.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mn2+: 3d5 Mn3+: 3d4 The electronic configuration of Mn2+is more stable than that of Mn3+. Hence, Mn2+ cannot be easily oxidised to Mn3+.

Multiple choice

Which of the following statements is false?

  1. A transition metal exhibits the highest oxidation state in oxides and fluorides.

  2. d1 configuration is very unstable in ions.

  3. In an aqueous medium, Cu+ is more stable than Cu2+.

  4. Manganese (III) is highly oxidizing in nature.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In an aqueous medium, Cu2+ is more stable than Cu+. Although energy is required to remove one electron from Cu+ to Cu2+, but the high hydration energy of Cu2+compensates for it. Therefore, Cu+ ion is not stable in aqueous solutions and disproportionate to give Cu2+ and Cu.

Multiple choice

Metal oxides that show basic as well as acidic behaviour are called amphoteric oxides. Oxides of which of the following elements are amphoteric?

a. Aluminium b. Zinc c. Copper

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct option. Oxides of aluminium and zinc metals show basic as well as acidic behaviour and are called amphoteric oxides. Their oxides react with acids as well as bases to form salt and water.