Tag: the p-block elements

Questions Related to the p-block elements

The two acids present in Chlorine water are:

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

  1. HCl, $H _2SO _4$

  2. HCl, $HNO _3$

  3. HCl, HOCl

  4. HCl, $HClO _4$

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Correct Option: C
Explanation:

Chlorine water
$CI _2+H _2O \rightarrow HOCI+HCI$

Chlorine does not support combustion.

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: B
Explanation:

Chlorine supports vigorous combustion of many elements to form their chlorides.

Which has maximum pH in aqueous solution ? 

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

  1. $NaClO$

  2. $NaClO _2$

  3. $NaClO _3$

  4. $NaClO _4$

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Correct Option: A
Explanation:

$NaClO$ has the maximum $pH$ because the acidic strength decreases with decreasing $O$ atoms in oxy acids . Since $NaClO$ has the lowest oxygen atom among given options, it will have least acidic strength and hence, a maximum $pH$.

Which one of the following anions can undergo both oxidation and reduction?

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

  1. $Cr _2{O _7}^{2-}$

  2. $N{O _3}^{-}$

  3. $OCl^-$

  4. ${S}^{2-}$

Show answer
Correct Option: C
Explanation:

$(A)$ In $Cr _2{O _7}^{2-}$, the oxidation state of $Cr$ is $+6$, which is maximum oxidation of $Cr$. It can only lower down its oxidation state. So, it acts only as an oxidising agent.
$(B)$ In $N{O _3}^{-}$, the oxidation state of $N$ is $+5$, which is the maximum oxidation of $N$. It can only lower its oxidation state  and so, it acts only as an oxidising agent.
$(C)$ In $OCl^-$, the oxidation state of $Cl$ is $+1$ and $Cl$ shows oxidation state from $-1$ to $+7$ and so, it can undergo both oxidation and reduction.
$(D)$ In ${S}^{2-}$, the oxidation state of $S$ is $-2$, which is the minimum oxidation state of $S$ and so, it can only increase its oxidation state and hence, it acts only as a reducing agent.

Therefore, $OCl^-$ can undergo both oxidation as well as reduction.

The correct order of basic character of oxo anions of chlorine is:

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

  1. $ Cl{O} _{ 4 }^{ - }>Cl{O} _{ 3 }^{ - }>Cl{O} _{ 2 }^{ - }>ClO^{ - }$

  2. $ ClO^- > Cl{O} _2^- > Cl{O} _3^- > Cl{O} _4^- $

  3. $ Cl{O} _3^- > Cl{O} _4^- > Cl{O} _2 > Cl{O}^- $

  4. $ Cl{O}^- > Cl{O} _2^- > Cl{O} _4^- > Cl{O} _3^- $

Show answer
Correct Option: B

The correct statement (s) regarding, $\left( i \right)\,\,HCIO\,\,\,\,\left( {ii} \right)\,\,\,HCI{O _2}\,\,\,\,\left( {iii} \right)\,\,\,HCI{O _3}$ and $\left( {iv} \right)\,\,\,HCI{O _4}$, is 

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

  1. The number of $CI=O$ bond in $(ii)$ and $(iii)$ together is two.

  2. The numbers of lone pairs of electrons on $CI$ in $(ii)$ and $(iii)$ together is three.

  3. The hybridization of $CI$ in $(iv)$ is $s{p^3}$.

  4. Amongst $(i)$ to $(iv)$, the strongest acid is $(i)$.

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Correct Option: B

Select the incorrect statement(s):

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

  1. ${NF _3}$ has a highest dipole moment among $CO$, ${NH _3}$ and ${NF _3}$

  2. $HF$ has a highest boiling point among ${CH _4}$, ${NH _3}$ and $HF$

  3. ${Cl _2}$ has a lowest boiling point among ${Cl _2}$, ${Br _2}$ and ${I _2}$

  4. ${HClO _3}$ is weakest acid among ${HIO _3}$, ${HBrO _3}$ and ${HClO _3}$

Show answer
Correct Option: A,D
Explanation:

HF has a highest boiling point due to strong H bonding.
$Cl _2$ has a lowest boiling point due to lowest molar mass.
$CO$ has highest dipole moment due to linear structure.

Mixture of $KBr$ and $KBrO _3$ in acidic medium can be used as brominating agent.

The chemical reaction is, $ 5Br^{-} + xBrO^{-} _3 + 6H^{+} \rightarrow 3Br _y + 3H _2O$

Then $ x+y$ is :

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

  1. 6

  2. 3

  3. 5

  4. 11

Show answer
Correct Option: B
Explanation:

Reaction of process:

$ 5Br^{-} + BrO _3^{-} + 6H^{+} \rightarrow 3Br _2 + 3H _2O$
      -1               +5                               0

$x$ = 1 ,$y$ = 2

$x +y$ = 3

Here, bromide ion oxidises and $BrO _3^-$ reduces and bromine forms as a product.

Which one of the following is not a true "per acid" ?

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

  1. $ HClO _4 $

  2. $ H _2SO _5 $

  3. $ H _2S _2O _8 $

  4. $ H _3PO _5$

Show answer
Correct Option: A
Explanation:

A peroxy acid is an acid which contains an acidic -OOH group. $HClO _4$ doesn't contain -OOH group.

Which of the following is the weakest  base as per the Bronsted concept ?

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]^-$

Show answer
Correct Option: A
Explanation:
The Bronsted-Lowry definition of an acid is a proton donator and a base is a proton acceptor. 

According to Bronsted concept, conjugate base of strongest acid is weakest.

order of acidity $HClO _4 > HClO _3 >HClO _2 > HClO$

so weakest base is $ClO _4^-$.