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Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Chlorine has two naturally occuring isotopes $ _{ 17 }^{ 37 }{ Cl }$ and $ _{ 17 }^{ 35 }{ Cl }$ and average atomic mass of chlorine is $35.5$. The percentage of $ _{ 17 }^{ 37 }{ Cl }$ is:

  1. 25%

  2. 75%

  3. 40%

  4. 60%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let x be the percentage of Cl-37. Then (100-x) is the percentage of Cl-35. The average atomic mass is (37x + 35(100-x))/100 = 35.5. Solving this gives 37x + 3500 - 35x = 3550, so 2x = 50, x = 25%.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Select the correct statement (s)

  1. HCI and HF do not from free radical easily due to larger bond-energy
  2. HI with a minimum bond energy is every reactive and instead from ${{\text{I}} _{\text{2}}}\,\,\,$

  3. Both (a) and (b)

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Bond dissociation energy with hydrogen decreased down the group so HI is will be the most reactive . HI is more reative because the bond dissociation energy is low due to difference in size of hydrogen and iodine so it can be easily breaked.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Addition of halogen $(C{l _2} or B{r _2})$ to alkenes goes through formation of :

  1. Carbocation

  2. Carbanion

  3. Cyclic halonium ion

  4. Carbon free radical
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electrophilic addition of halogens to alkenes involves the formation of a cyclic halonium ion intermediate, which explains the anti-addition stereochemistry observed in these reactions.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

In which of the following, oxidation number of chlorine is $ + 5 ?$

  1. $Cl _{2}O _{7}$
  2. $\mathrm { ClO } _ { 3 } ^ { - }$
  3. $\mathrm { CHO } ^ { - }$
  4. $\mathrm { ClO } _ { 4 } ^ { - }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Oxidation number of $Cl _2O _7$:-

   $2x-14=0$
$x=7$

Oxidation number of ${ClO _3}^{-}$:-
$x-6=-1$
$x=5$
Oxidation number of $ClO^-$:-
$x-2=-1$
$x=1$
Oxidation number of ${ClO _4}^-$:-

$x-8=-1$
$x=7$
hence option B is correct.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Compare oxygen and flourine in Ionic radius$\quad O^{2-} , F^-$:

  1. $\space O^{2-} = F^-$
  2. $\space O^{2-} < F^-$
  3. $\space O^{2-}> F^-$
  4. $\space O^{2-} \geq F^-$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Among the elements of same period the ion with more number of electrons and less number of protons is having more radius.If the number of electrons are same the ion with less number of protons is having more radius.

Here $\quad O^{2-} $and $ F^-$ both are having same 10 electrons but oxygen is having 8 protons(which can atrract outer electrons with less force than florine) and florine is having 9 protons.So the ionic radius of $\space O^{2-}>  F^-$

Hence option C is correct.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Oxidation of hydrogen halide, HX affords a method for the industrial and laboratory preparation of the halogen, $X _2$, in the free state in respect of all of the following except :

  1. fluorine.

  2. chlorine.

  3. bromine.

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

Due to higher electronegativity, HF doesn't follow such reaction and fluorine doesn't form.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Which of the following is incorrect statement? 

  1. Bond dissociation energy of Bromine is more than that of chlorine.

  2. The standard electrode potential of chlorine is more than that of fluorine.

  3. The percentage of chlorine in bleaching powder compound is 35-38%.

  4. All
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bond dissociation:
$Cl _{2} > Br _{2}$
Standard electrode potential:
$F>Cl$
Bleaching powder $(Ca(ClO) _{2})$             

Percentage of $Cl = \frac{35.5\times 2}{(35.5+16)\times 2 +40}$
$=\frac{71}{143}\times 100 \simeq 50$%

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

The correct order of reactivity is:

  1. $\mathrm{F}>\mathrm{Cl}>\mathrm{B}\mathrm{r}> \mathrm{I} $
  2. $\mathrm{F}<\mathrm{Cl}<\mathrm{B}\mathrm{r}<\mathrm{I}$
  3. $\mathrm{F}<\mathrm{Cl}>\mathrm{B}\mathrm{r}>\mathrm{I}$
  4. $\mathrm{F}>\mathrm{Cl}<\mathrm{B}\mathrm{r}<\mathrm{I}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As we move down the group chemical reactivity decreases due to decrease in electronegativity