Tag: p- block elements-ii

Questions Related to p- block elements-ii

Choose the correct oxidation states of Chlorine in species: 

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

  1. (a) $\displaystyle { HOCl }- +1$

  2. (b) $\displaystyle { HOCl }O- +3$

  3. (c) $\displaystyle { HOBr }- +3$

  4. (d) $\displaystyle { HOBrO } _{ 2 }- +5$

  5. (e) $\displaystyle { HOIO } _{ 3 }- +7$

  6. (f) $\displaystyle { HOClO } _{ 3 }- +5$

  7. None of the above

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

(a) hypochlorous acid +1
(b) chlorous acid +3
(c) hypobromous acid +1
(d) bromic acid +5
(e) periodic acid +7
(f) perchloric acid +7

Select the incorrect order(s) among the following :

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

  1. $ClO^- < BrO^- < IO^-$ - disproportionation

  2. $ClO _4^- < BrO _4^- < lO _4^-$ - oxidising power

  3. $HClO < HClO _2 < HClO _3 < HClO _4$ - acid strength

  4. $HOCl > HOI > HOBr$ - acid strength

Show answer
Correct Option: B,D
Explanation:

1) The reduction potential values are as follows:
$ClO _4^-: 1.19\ V$,
$BrO _4^-: 1.65\ V$,
$BrO _4^-: 1.74\ V$.
So, the order of oxidising power is: $ClO _4^- < IO _4^- < BrO _4^-$.
2) The correct order of acidic strength is: $HOCl < HOBr < HOI$. As the electronegativity of halogens increases, the acidic character also increases.

The reaction, $3ClO _{(aq.)}^-\rightarrow ClO _{3(aq.)}^-+2Cl^- _{(aq.)}$ is an example of :

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

  1. oxidation reaction.

  2. reduction reaction.

  3. disproportionation.

  4. decomposition reaction.

Show answer
Correct Option: C
Explanation:
  1. Disproportionation is a specific type of redox reaction in which a species is simultaneously reduced and oxidised to form two different products.
    Here the $ClO^{-}$ is simultaneously reduced and oxidised to form two different products.

    Hence option C is correct.

When bleaching powder is treated with mineral acids,the gas evolved is:

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

  1. $Cl _2$

  2. $O _2$

  3. $H _2$

  4. none of these

Show answer
Correct Option: A
Explanation:

When bleaching powder is treated with mineral acids ${ Cl } _{ 2 }$ gas evolved

When Halogens are treated with hot and conc. alkalis,major products formed are:

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

  1. Hypohalite

  2. Halite

  3. Halate

  4. Halide

Show answer
Correct Option: C,D
Explanation:

Halogen are treated with hot and conc. alkalis, major products formed are Halate and halide.

When bromate salt are reacted with fluorine in alkaline solution,which salt is formed?

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

  1. Bromide

  2. Bromous

  3. Hypobromous

  4. Perbromate

Show answer
Correct Option: D
Explanation:
(bromate salt)  ${ Br }{ O } _{ 3 }^{ - }+{ F } _{ 2 }\left( g \right) +{ 2OH }^{ - }\longrightarrow { Br }{ O } _{ 4 }^{ - }+{ H } _{ 2 }O+2{ F }^{ - }$  (perbromate)
Perbromate is the sluggish oxidant. Although it is more active than the Perchlorate ion in the agneous solution.

When slaked lime is treated with chlorine, a compound is formed. Which of the following is correct about that compound? 

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

  1. It is used in bleaching cotton.

  2. It is used as disinfectant.

  3. It is a halide.

  4. It is used for sterilization of water.

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

Calcium hydroxide react with chlorine to give calcium hipochlorite, calcium chloride and water. Calcium hipochlorite which is formed in the reaction is used as bleaching agent, disinfevtant and in the sterilization process.

$2Ca(OH) _2 + 2Cl2 \rightarrow Ca(ClO) _2 + CaCl _2 + 2H _2O$.

Hence option A,B,C are correct.

The weakest $Cl-O$ bond is found in :

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

  1. $ClO _{4}^{-}$

  2. $ClO _{2}^{-}$

  3. $ClO^{-}$

  4. $ClO _{3}^{-}$

Show answer
Correct Option: C
Explanation:

The anions given are conjugate bases of acids. According to Lowry Bronsted concept, a strong acid has weak conjugate base and a weak acid has a strong conjugate base. These anions are stabilised to greater extent, it has lesser attraction for proton and therefore, will behave as weaker base (lesser tendency for the reaction to go in backward direction). Consequently, the corresponding acid will be strongest because weak conjugate base has strong acid and strong conjgate base has weak acid and vice versa. The charge stabilization increases in the order : $ClO^- < ClO _2^- < ClO _3^- < ClO _4^-$. This means that $ClO^-$ will have minimum stability and therefore, will have maximum attraction for $H^+$. In other words $ClO^-$ will be strongest base and so its conjugate acid HClO will be the weakest acid.

Which one is most stable to heat :

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

  1. $HClO$

  2. $HClO _{2}$

  3. $HClO _{3}$

  4. $HClO _{4}$

Show answer
Correct Option: D
Explanation:

The thermal stability of the oxyacids of halogens increases with increase in the oxidation state of halogen or with increase in the number of oxygen atoms.
 This is due to involvement of more electrons in the formation of sigma and pi bonds. The multiplicity of the Cl-O bond increases.
Thus the increasing order of the thermal stability is $HClO <HClO _2 <HClO _3<HClO _4$. Thus, $HClO _4$ is most stable to heat.

Hypervalent ion is/are :

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

  1. $SO _3^{2-}$

  2. $PO _4^{3-}$

  3. $SO _4^{2-}$

  4. $ClO _4^{-}$

Show answer
Correct Option: B,C,D
Explanation:
Hypervalent molecule -
The hypervalent molecule is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells.

 Explanation -
A. Valence electrons available in $(SO _3)^{2-}$ => 8
B. Valence electrons available in $(PO _4)^{3-}$ => 10
C. Valence electrons available in $(SO _4)^{2-}$ => 12
D. Valence electrons present  in $(ClO _4)^-$ => 14

Hence B, C, D are hypervalent compounds.