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

The formula of calcium oxide is

  1. CaO2

  2. CaO

  3. CaO3

  4. CI
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Calcium oxide has the chemical formula CaO. Calcium has a +2 charge and oxygen has a -2 charge, so they combine in a 1:1 ratio to form a neutral compound.

Multiple choice

The chemical formula for wulfenite mineral is

  1. FeCO3

  2. (Fe,Mn)WO4

  3. PbMoO4

  4. SnO2

  5. FeCr2O4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Wulfenite is a lead molybdate mineral with the formula PbMoO4. It is most often found as thin tabular crystals with a bright orange-red to yellow-orange colour, sometimes brown, although the colour can be highly variable.

Multiple choice

What is the oxidation number of Cr in CrO4–2 ion?
    • 1
    • 2
    • 4
    • 6
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the chromate ion (CrO4^2-), oxygen has an oxidation number of -2. Since there are 4 oxygen atoms contributing -8 total and the ion has a -2 charge, the chromium must be +6 to balance: +6 + (-8) = -2.

Multiple choice

Oxygen molecule exhibits

  1. paramagnetism

  2. diamagnetism

  3. ferromagnetism

  4. ferrimagnetism
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Oxygen (O2) exhibits paramagnetism because it has two unpaired electrons in its molecular orbital configuration. Paramagnetic substances are weakly attracted to magnetic fields due to unpaired electrons. This is why liquid oxygen can be held between the poles of a magnet.

Multiple choice

What is the oxidation sate of K in KO2?

  1. +2

  2. -2

  3. +1

  4. -1
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because superoxide species is represented as O2- since compound on a awhole is neutral hence oxidation state of potassium is +1.

Multiple choice

Electron affinity is positive when

  1. O- is formed from O

  2. O2- is formed from O

  3. O+ is formed from O

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Oxygen needs two electrons to complete its octet. So, electron affinity is positive when O2- is formed from O.

Multiple choice

Match the column – I (transition metal element) with column – II (most stable oxidation state) and select the correct option.

 
Column – I
Column – II
P. Cadmium 1. +1
Q. Ruthenium 2. +2
R. Silver 3. +3
S. Zirconium 4. +4

  1. P - 2, Q - 1, R - 3, S - 4

  2. P - 2, Q - 3, R - 1, S - 4

  3. P - 3, Q - 1, R - 4, S - 2

  4. P - 3, Q - 4, R - 2, S - 1

  5. P - 4, Q - 2, R - 3, S - 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The most stable oxidation state of cadmium is +2. The most stable oxidation state of silver is +1. The most stable oxidation state of ruthenium is +3. The most stable oxidation state of zirconium is +4.