Chemistry

Oxidation States and Oxides

308 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 group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

When $I^-$ is oxidised by $Mn{O}^- _4$ in alkaline medium, $I^-$ converts into :

  1. $\mathrm{I}\mathrm{O} _{3}^{-}$
  2. $\mathrm{I} _{2}$
  3. $\mathrm{I}\mathrm{O} _{4}^{-}$
  4. $\mathrm{I}\mathrm{O}^{-}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$2\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O} _{4}+2\mathrm{K}\mathrm{O}\mathrm{H}\rightarrow 2\mathrm{K} _{2}\mathrm{M}\mathrm{n}\mathrm{O} _{4}+\mathrm{H} _{2}\mathrm{O}+\mathrm{O}$
$\frac{2\mathrm{K} _{2}\mathrm{M}\mathrm{n}\mathrm{O} _{4}+2\mathrm{H} _{2}\mathrm{O}\rightarrow 2\mathrm{M}\mathrm{n}\mathrm{O} _{2}+4\mathrm{K}\mathrm{O}\mathrm{H}+2\mathrm{O}}{2\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O} _{4}+\mathrm{H} _{2}\mathrm{O}\xrightarrow[]{alkalme}2\mathrm{M}\mathrm{n}\mathrm{O} _{2}+2\mathrm{K}\mathrm{O}\mathrm{H}+3[\mathrm{O}]}$
$\frac{KI+[\mathrm{O}] \rightarrow \mathrm{K}\mathrm{I}\mathrm{O} _{3}}{2\mathrm{K}\mathrm{M}\mathrm{n}\mathrm{O} _{4}+\mathrm{K}\mathrm{I}+\mathrm{H} _{2}\mathrm{O}\rightarrow 2 KOH +2\mathrm{M}\mathrm{n}\mathrm{O} _{2}+\mathrm{K}\mathrm{I}\mathrm{O} _{3}}$
$KI+3[O]\rightarrow KIO _3^{-}$
Hence option A is correct.

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Which of the following metal oxides are reduced by self reduction method?

  1. $Cu _2O$
  2. $PbO$
  3. $HgO$
  4. $CaO$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Self-reduction process:  This process is also called auto reduction process or air reduction process. 


The sulphide ores of less electropositive metals like Hg, Pb, Cu etc. are heated in the air as to convert part of the ore into oxide or sulphate which then reacts with the remaining sulphide ore to give the metal and sulphur dioxide. 


No external reducing agent is used in this process.

Hence options A,B & C are correct options.
Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Metal oxide can be reduced by __________.

  1. $Fe$
  2. $Sn$
  3. $C$

  4. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metal oxide of the low reactivity can be reduced by carbon in the simple extraction process. For example; lead oxide is reduced by carbon and it extract lead from its ore.

$2PbO(l) + C(s)  \rightarrow 2Pb (s) + CO _2 (g)$

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

From the following identify the correct ones.

  1. $Fe _2O _3 + 3CO \rightarrow 2Fe + 3CO _2$
  2. $ZnO + C \rightarrow Zn + CO$
  3. $Ca _3(PO _4) _2 + C \rightarrow P$
  4. $PbO + C \rightarrow Pb$
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

The correct reactions are as follows-

$Fe _2O _3+3CO\longrightarrow 2Fe+3CO _2$ in Blast furnace.
$ZnO+C\longrightarrow Zn+CO$
$PbO+C\longrightarrow Pb$
$ZnO+C$ and $PbO+C$ can be reduced with carbon.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

What is the value of $n$ in the following equation?


$Cr\left( OH \right) _{ 4 }^{ - }+OH^{ - }\longrightarrow  Cr{ O } _{ 4 }^{ 2- }+H _{ 2 }O\ +\ ne^-$

  1. $3$
  2. $6$
  3. $5$
  4. $2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the given half-reaction, chromium changes its oxidation state from +3 in Cr(OH)4(-) to +6 in CrO4(2-). This change involves the loss of 3 electrons, meaning n = 3.

Multiple choice imperfections in solids solid state the solid state chemistry

Fill in the blanks by choosing an appropriate option. A sample of ferrous oxide has actual formula $Fe {0.93}O _{1.00}.$ In this sample __(i) fraction of metal ions are $Fe^+$ ions. ____(ii) type of non-stoichiometric defect is present in this sample. 

  1. (i) 0.849 (ii) Metal deficiency

  2. (i) 0.790 (ii) Metal deficiency

  3. (i) 0.145 (ii) Metal excess

  4. (i) 0.93 (ii) Vacancy defect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given, sample of ferrous oxide is $Fe _{0.93}O _{1.00}$.

Let number of $Fe^{2+}$ ions is $x$ then number of $Fe^{3+}$ ions is $(0.93-x)$

Now, for electrical neutrality, $(+2)x + (+3)(0.93-x)=+2$

$\Rightarrow 2x+2.79 – 3x = 2$

$\Rightarrow x=0.79$

So, number of $Fe^{2+}$ ions $=0.79$

Number of $Fe^{3+}$ ions $=0.14$

So, fraction of $Fe^{2+}$ ions $= \cfrac {0.79}{0.93}=0.849$

$FeO$ has non stochiometric metal deficiency defect in which number of $Fe^{2+}$ ions are lesser than $O^-$ ions as compared to stochiometric formula. The neutrality is maintained to variable oxidation state possessing capability of $Fe$.

Multiple choice imperfections in solids solid state the solid state chemistry

Iron (II) oxide is written as $\overline{FeO}$. What does it mean?

  1. Fully pure

  2. Impure
  3. Ratio of $Fe$ and $O $ is 1:1

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

Impurity defects are foreign atoms that replace some  of the atoms making up the solid or that squeeze into the interstices; they are important in the electrical behaviour of semiconductors, which are materials used in computer chips and other electronic devices.

An example of interstitial impurity  atoms is the carbon atoms that are added to iron to make steel.

Multiple choice imperfections in solids solid state the solid state chemistry

Formula of metal oxide with metal deficiency defect in its crystal is $A _{0.8}O$. The crystal contains $A^{2+}$ and $A^{3+}$ ions. The fraction of metal existing as $A^{2+}$ ions in the crystal is

  1. $0.96$
  2. $0.04$
  3. $0.50$
  4. $0.31$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Solution:- (C) $0.50$

Fiormula is ${A} _{0.8}O$
So the ratio of $A : O = 80 : 100$
Thus, if there are $100$ atoms of oxygen then $80$ atoms of $A$.
Let $x$ be the no. of atopms of ${A}^{+2}$.
No. of atoms of ${A}^{+3} = 80 - x$
Charge on $A \; =$ Charge on $O$
Since oxygen has charge $-2$.
Therefore,
$2x + 3 \left( 80 - x \right) = 2 \times 100$
$2x + 240 - 3x = 200$
$\Rightarrow x = 40$
Therefore,
Fraction of ${A}^{+2} = \cfrac{\text{atoms of } {A}^{+2}}{\text{Total no. of atoms}}$
$\Rightarrow$ Fraction of ${A}^{+2} = \cfrac{40}{80} = 0.50$

Multiple choice imperfections in solids solid state the solid state chemistry

The non-stoichiometric compound, titanium monoxide has a continuous range of composition from $Ti _{0.75}O$ to $TiO _{0.69}$ Which of the following is/are the correct regarding the possible composition of the compound ? $[Ti=48]$

  1. The maximum percentage by mass of oxygen in the compound is $30.8$
  2. The minimum percentage by mass of titanium in the compound is $69.2$
  3. The minimum percentage by mass of oxygen in the compound is $18.7$
  4. The minimum percentage by mass of titanium in the compound is $82.3$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Multiple choice imperfections in solids solid state the solid state chemistry

Which of the following defect is seen in $FeO ?$

  1. Metal deficiency defect

  2. Metal excess defect

  3. Displacement defect

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

$FeO$ shows metal deficiency defect. In crystal of $FeO$ some $Fe^{2+}$ cations are missing and the loss of positive charge is made up by the presence of required number of $Fe^{3+} $ ions.

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

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