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

Which of the following oxides is acidic in nature?

  1. Na2O

  2. SO2

  3. MgO

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

Oxides of metals are basic in nature and on reaction with water, they produce bases. Sodium, magnesium and copper are metals. Therefore, Na2O, MgO and CuO are basic oxides. Sulphur is a non-metal and oxides of non-metals are either acidic or neutral. Therefore, SO2 is an acidic oxide as it reacts with water to produce an acid.

Multiple choice

Which of the following statements are false?

P. Fe3+ is less stable than Fe2+. Q. Mn2+ can be easily oxidised to Mn3+. R. Mn shows the greatest variation in possible oxidation numbers among 3d series elements. S. The correct electronic configuration of Cr is 3d54s1.

  1. P and Q

  2. P and R

  3. P and S

  4. Q and R

  5. R and S
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The electronic configuration of Fe3+ is more stable than that of Fe2+. The electronic configuration of Mn2+ is more stable than that of Mn3+. Hence, Mn2+ cannot be easily oxidised to Mn3+.

Multiple choice

What is the correct increasing order of electronegativity for the most common oxidation states among the following elements?

  1. F < O < N < C

  2. O < N < C < F

  3. C < N < F < O

  4. C < N < O < F
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Electronegativity increases across a period and within a group. The correct increasing order is carbon (2.55) < nitrogen (3.04) < oxygen (3.44) < fluorine (3.98), which is the most electronegative element. Fluorine has the highest electronegativity value of all elements.

Multiple choice

Dichromate ion in acidic medium oxidise stannous ion as: xSn2+ + yCr2O72– + zH+ → aSn4+ + bCr3+ + cH2O for the above reaction,

  1. the value of x : y = 1 : 3

  2. the value of x + y + z = 18

  3. a : b = 2 : 3

  4. the value of z – c = 5

  5. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction can be given as: Reduction half→Cr2O72– + 14H+ + 6e →  2Cr3+ + 7H2O Oxidation half→[Sn2+ – 2e → Sn4+]*3 So the balanced chemical equation is 3Sn2+ + Cr2O72– +14H+ = 3Sn4+ + 2Cr3+ + 7H2O therefore, x + y + z = 18, hence this is a correct option.  

Multiple choice

Which of the following statements is INCORRECT?

  1. Pyrolusite is an ore of manganese.

  2. Manganese is more stable in +3 state than in +2 state.

  3. Mn(II) ion shows maximum paramagnetic character among bivalent ions of first transition series.

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

  5. Mn is in zero oxidation state in Mn2(CO)10.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Manganese is more stable in the +2 state than in +3 state.

Multiple choice

Correct order of acidic character of oxides of manganese is

  1. MnO < MnO2 < Mn2O3 < Mn2O7

  2. Mn2O7 < Mn2O3 < MnO2 < MnO

  3. MnO < Mn2O3 < MnO2 < Mn2O7

  4. MnO < Mn2O3 < Mn2O7 < MnO2

  5. Mn2O3 < MnO2 < MnO < Mn2O7
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Correct order of acidic behaviour is Mangnese(II) oxide < Manganese(III) oxide < Manganese(IV) oxide < Manganese(VII) oxide.