Tag: oxoacids of halogens

Questions Related to oxoacids of halogens

Which of the following has more acidic in nature?

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. HClO

  2. HClO$ _2$

  3. HClO$ _3$

  4. HClO$ _4$

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Correct Option: D
Explanation:
Acidity of oxyacids of halogen increases with increase in oxidation number of halogen Oxidation number of CI in HCIO is + 1, HCIO$ _2$ is +3, HClO$ _3$ is + 5 and HCIO$ _4$ is + 7.
$\therefore$ HClO$ _4$ is most acidic among given choices.

Assertion: $HClO _4$ is a strong acid than $HClO _3$.
Reason: Oxidation state of Cl in $HClO _4$ is +7 and in $HClO _3$, it is + 5.

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. If both assertion and reason are true and the reason is a correct explanation of the assertion.

  2. If both assertion and reason are true but reason is not a correct explanation of the assertion

  3. If the assertion is true but reason is false

  4. If both the assertion and reason are false

  5. If the assertion is false but the reason is true

Show answer
Correct Option: A
Explanation:

Let us calculate the oxidation state of Cl in $HClO _4$ ;

$+1+ x + $ ($4 \times (-2)$ = 0
So,$ x = -1+8$
         $  = 7$
Hence. the oxidation state of Cl in $HClO _4$ is 7.
Let us calculate the oxidation state of Cl in $HClO _3$ ;
$+1+ x + $ ($3\times (-2)$ $= 0$

So, $x = -1+6$
         $= 5$
Hence. the oxidation state of Cl in $HClO _4$ is 5.

So, we conclude that the oxidation state of Cl is less  in $HClO _3$ than $HClO _4$

Bleaching powder loses its power on keeping for long time because :

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. it changes to calcium hypochlorite.

  2. it changes to calcium chloride and calcium hydroxide.

  3. it absorbs moisture.

  4. it changes to calcium carbonate and chlorine.

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Correct Option: D
Explanation:

Bleaching powder reacts with carbon dioxide in air to give chlorine and calcium carbonate.

$2Ca(ClO) _2 + 2CO _2 \rightarrow 2CaCO _3 + 2Cl _2 + O _2$

Choose the correct order of acidity order:

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. $\displaystyle { HClO < { HClO } _{ 2 } }$

  2. $\displaystyle { H } _{ 2 }{ SO } _{ 4 } > { H } _{ 2 }{ SO } _{ 3 }$

  3. $\displaystyle { H } _{ 3 }{ PO } _{ 2 } < { H } _{ 3 }{ PO } _{ 3 }$

  4. $\displaystyle { HNO } _{ 3 } > { HNO } _{ 2 }$

  5. $\displaystyle { HF > { HCl } }$

  6. $\displaystyle { H } _{ 3 }{ PO } _{ 3 } > { H } _{ 3 }{ PO } _{ 4 }$

Show answer
Correct Option: A,B,D,F
Explanation:

The acidic character of oxyacids increases with increase in the oxidation state. 


More is the number of $O$ atoms bonded, more electrons will be pulled away from $O-H$ bond, weaker will be the $O-H$ bond and stronger will be the acid. Hence, $\displaystyle
HClO < HClO _2$, $\displaystyle H _2SO _4 > H _2SO _3$ and $\displaystyle HNO _3 > HNO _2$

For options C and F, the correct order is $\displaystyle H _3PO _2 < H _3PO _4 < H _3PO _3$ because  $H _3PO _3$ is polar.

The increase in the acidity is small as the number of unprotonated oxygen, responsible for the enhancement of acidity due to inductive effect remains the same. $HCl$ is more acidic than $HF$ due to strong $H-F$ bond (high bond dissociation enthalpy), high heat of dehydration for $HF$ due to an association in solution due to hydrogen bonding and low electron affinity of fluorine atom.

What are the corresponding anhydrides of the following oxyacids:

$\displaystyle { HClO } _{ 4 }$, $\displaystyle { HClO } _{ 3 }$, $\displaystyle { HClO } _{ 2 }$ and $\displaystyle { HOCl }$.

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. $\displaystyle { HClO } _{ 4 }:{ Cl } _{ 2 }{ O } _{ 3 }$

  2. $\displaystyle { HClO } _{ 3 }:{ Cl } _{ 2 }{ O } _{ 6 }$

  3. $\displaystyle { HClO } _{ 2 }:{ Cl }O _{ 2 }$

  4. $\displaystyle { HOCl }:{ Cl } _{ 2 }{ O _4 }$

Show answer
Correct Option: B,C
Explanation:
Anhydrides of oxyacids are given as:

$\displaystyle { HClO } _{ 4 }:{ Cl } _{ 2 }{ O } _{ 7 }$

$\displaystyle { HClO } _{ 3 }:{ Cl } _{ 2 }{ O } _{ 6 }$

$\displaystyle { HClO } _{ 2 }:{ Cl }O _{ 2 }$

$\displaystyle { HOCl }:{ Cl } _{ 2 }{ O }$