Tag: p-block elements

Questions Related to p-block elements

Acid strength of oxoacids of halogen is in order :

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

  1. $ HOF > HOCl > HOBr > HOI $

  2. $ HOI < HOBr < HOCl <HOF $

  3. $ HOI > HOCl > HOBr > HOF $

  4. $ HOCl > HOBr > HOI > HOF $

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Correct Option: B
Explanation:

 The acidic strength of the hypohalous acids increases in the order  : HOI <HOBr <HOCl < HOF.


It is because the electronegativity of halogen decreases down the group.

In the conversion of $BrO _3 \ ^- $ to $ BrO _4 \ ^- $:

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

  1. there is no change in oxidation number

  2. reduction takes place in basic solution

  3. reduction also takes place by $XeF _2$

  4. equivalent mass of $ Br{ O }^- _3$ is one-half of ionic mass

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Correct Option: D
Explanation:

A. During the conversion of $BrO^- _3\ to\ BrO^- _4$, the oxidation number of bromine changes from +5 to +7. Hence, the option A is incorrect.
B. and C.  Since there is an increase in the oxidation number, the net reaction is the oxidation of bromine. Hence, the options B and C are incorrect.
D. The equivalent mass of $BrO^- _3$ is the ratio of the ionic mass to the change in the oxidation number. It is tone half of the ionic mass as the change in the oxidation number is 2. Thus, the option D is correct.

${ FClO } _{ 3 }$ (perchloryl fluoride) has the highest dielectric constant.

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

  1. True

  2. False

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Correct Option: A
Explanation:

The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.
As the dielectric constant increases, the electric flux density increases, if all other factors remain unchanged. This enables objects of a given size, such as sets of metal plates, to hold their electric charge for long periods of time, and/or to hold large quantities of charge. 
Due to higher electronegativity constituent atoms, $FClO _3$ have very high dieelectric constant.

Chlorous acid is unstable and decomposes into :

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

  1. $\displaystyle { HCl,\quad { ClO } _{ 2 } }$

  2. $\displaystyle { HCl,\quad { Cl } _{ 2 } }$

  3. $\displaystyle { HOCl,\quad { ClO } _{ 2 } }$

  4. $\displaystyle { HOCl,\quad { Cl } _{ 2 } }$

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Correct Option: A
Explanation:
It fresh solution is colourless but soon it turns yellow due to formation of $ClO _{2}$

$5HClO _{2}\rightarrow 4ClO _{2}+HCl+2H _{2}O$

The set with correct order of acidity is:

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

  1. $HClO < HClO _2 < HClO _3 < HClO _4$

  2. $HClO _4 < HClO _3 < HClO _2 < HClO$

  3. $HClO < HClO _4 < HClO _3 < HClO _2$

  4. $HClO _4 < HClO _2 < HClO _3< HClO$

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Correct Option: A
Explanation:

Conjugate base of $HClO, HClO _2, HClO _3, HClO _4$ are  $CLO^-, {ClO _2}^-, {ClO _3}^-, {ClO _4}^-$.


When the atom's size is big, the stability will be more. Hence ${ClO _4}^-$ will be more stable and  ${ClO}^-$ will be the least.

If the conjugate base of an acid is stable, the acid will be stronger (can easily donate protons).

Hence the order will be:

$HClO < HClO _2 < HClO _3 < HClO _4$

The following acids have been arranged in order of decreasing acid strength. Identify the correct order ClOH(I), BrOH(II), IOH(III)

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

  1. I > II> III

  2. II > I > III

  3. III > II > I

  4. I > III > II

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Correct Option: A
Explanation:

As we move down the group basic nature of hydroxides of halogens increases so correct order of decreasing acid strength of hydroxides of halogens is I > II> III
Hence option A is correct.

On heating $KClO _3$, we get :

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

  1. $KClO _2+O _2$

  2. $KCl+O _2$

  3. $KCl+O _3$

  4. $KCl+O _2+O _3$

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Correct Option: B
Explanation:
On heating $KClO _3$, we get $KCl+O _2$.

The reaction is as follows:
$2KClO _3 \longrightarrow 2KCl+ 3O _2$

When potassium chlorate is heated in the presence of manganese dioxide catalyst, it decomposes to form potassium chloride and oxygen gas. 

The ion that cannot undergo disproportionation is :

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

  1. $ClO _4^-$

  2. $ClO _3^-$

  3. $ClO _2^-$

  4. $ClO^-$

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Correct Option: A
Explanation:

$ClO _4^-$
+7
here, Cl is in highest oxidation state so further it can not be oxidise so it can not undergo disproportionation reaction.

Which products are expected from the disproportionation of hypochlorous acid?

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

  1. $HClO _3$ and $Cl _2O$

  2. $HClO _2$ and $HClO _4$

  3. $HCl $and $Cl _2O$

  4. $HCl $ and $HClO _3$

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Correct Option: D
Explanation:
$\displaystyle 3HClO \rightleftharpoons 2HCl + HClO _3$

It is a disproportionation reaction of hypochlorous acid where the oxidation number of chlorine from $+1$ to $-1$

Higher is Oxidation no. more is effective nuclear charge, lesser is size.

The disproportionation of hypochlorous acid gives $\displaystyle HCl $ and $\displaystyle HClO _3 $.

Hence option D is correct.

The following acids have been arranged in the order of decreasing acid strength. Identify the correct order: ClOH (I), BrOH (II), IOH (III).

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

  1. $I> II > III$

  2. $II>I>III$

  3. $III>II>I$

  4. $I>III>II$

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Correct Option: A
Explanation:

For the same oxidation state, when the electronegativity of the halogen increases, the strength of the oxyacid increases.
$HOCI > HOBr > HOI$

Hence option A is correct.