Tag: p-block elements

Questions Related to p-block elements

State whether the given statement is true or false:

In Japan Sunami, there has been increase in radioactive iodine content in salt.
group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. True

  2. False

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Correct Option: A
Explanation:

The given statement is True. 
In Japan Sunami, there has been increase in radioactive iodine content in salt.
Traces of iodine are found in mineral deposits. Iodine also finds its way into the animal system as thyroxin in thyroid glands.

In very recent Sunami in Japan, food materials were banned as they were contaminated with radioactivity . Which of the following was found to have radioactive beyond prescribed limit ?

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. F

  2. Cl

  3. I

  4. At

Show answer
Correct Option: C
Explanation:

Tokyo, the city first reported a spike of radioactive iodine in its water supply on March 23, 2011 at levels below the limit for adults but above the threshold of safety for infants; since then, iodine levels in Tokyo's water have declined below both thresholds. 


Above-limit levels of radioactive iodine and cesium have also been found in milk and vegetables in seven prefectures in Japan. 

Hence,option C is correct.


$O _2^+PtF _6^-$ is an orange-coloured compound.

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Dioxygenyl hexafluoroplatinate $(O _2^+[PtF _6]^-)$ is a orange coloured salt. It is a solid and is used to prepare co-ordination complexes.

The odd one is:

[note: valency is not a criterion]

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. iodine

  2. sulphur

  3. phosphorus

  4. carbon

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Correct Option: A
Explanation:

Catenation,  chemical linkage into chains of atoms of the same element, occurring only among the atoms of an element that has a valence of at least two and that forms relatively strong bonds with itself. The property is predominant among carbon atoms, significant among sulfur and silicon atoms, and slightly present among germanium, nitrogen, selenium, and tellurium atoms.
here, apart from iodine all other have this property.

Which halogen can be purified by sublimation?

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. $F _2$

  2. $Cl _2$

  3. $Br _2$

  4. $I _2$

Show answer
Correct Option: D
Explanation:

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase..
At room temperature, fluorine and chlorine are gases, bromine is liquid, and iodine is solid. They form diatomic molecules in the pure state. Since, $I _2$ is solid at room temperature. It will be sublimated and remaining can not be sublimated
Hence, options D is correct.

The decreasing order of bond dissociation energy among halogens is:

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. $\mathrm{F}-\mathrm{F} >\mathrm{C}\mathrm{l}$ -$\mathrm{C}\mathrm{l}> \mathrm{B}$r - $\mathrm{B}$r $>I-I$

  2. $\mathrm{C}\mathrm{l}$ -$\mathrm{C}\mathrm{l}> \mathrm{B}$r - $\mathrm{B}$r $>\mathrm{F}-\mathrm{F}>I-I$

  3. $\mathrm{C}\mathrm{l}$ -$\mathrm{C}\mathrm{l}> \mathrm{B}$r - $\mathrm{B}$r $>I-I>\mathrm{F}-\mathrm{F}$

  4. $I-I>\mathrm{F}-\mathrm{F}>\mathrm{C}\mathrm{l}$ -$\mathrm{C}\mathrm{l}> \mathrm{B}$r - $\mathrm{B}$r

Show answer
Correct Option: B
Explanation:

Bond dissociation energy decrease
down the group
But bonds dissociation energy of 
$F _2$ is less than excepted due to 
large repulsion of $e^-$ in $F _2$


Which of the statements is/are true about the reactivity order is $F _2\, >\, Cl _2\, >\, Br _2\, >\, I _2.$
I. Lower the activation energy for the chain initiation step, more reactive is the halogen.
II. Lower the activation energy for the first chain propagation step, more reactive is the halogen.
III. More negative is the overall heat of the reaction $(\Delta H _{\zeta}^{})$ of halogenation of alkane, more reactive is the halogen.
IV. Lower the activation energy for the second chain-propagation step, more reactive is the halogen.

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. (I), (II)

  2. (I), (II), (III)

  3. (II), (III)

  4. (II), (III), (IV)

Show answer
Correct Option: C
Explanation:

There are two factors that determine the reactivity of the halogenation of alkanes.
1. Lesser the positive value of $E _{act}$ of the first chain propagating step, more reactive is the halogen.
2. Higher the negative value of overall heat of reaction $(\Delta H _{\zeta}^{})$ more reactive is the halogen. This explains high reactivity and explosive violence with which $F _2$ reacts with $CH _4$.

Iodine gas turns strach iodide paper :

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. Blue

  2. Red

  3. Colourless

  4. Yellow

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Correct Option: A
Explanation:

Iodine reacts with starch to produce a blue/black color.

The order of basicity of halides is :

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. $Cl < Br < I < F$

  2. $F < I < Br < Cl$

  3. $I < Br < Cl < F$

  4. $Cl < F < I < Br$

Show answer
Correct Option: C
Explanation:

Base is an electron pair donor. The more available the electrons, the more readily they can be donated to form a new bond to the proton and, and therefore the stronger base. When comparing atoms within the same group of the periodic table, the larger the atom the weaker the H-X bond and the lower the electron density making it a weaker base.

Therefore the order of basicity is $F>Cl>Br>I$

 Essential trace element involved in physiology of thyroid glands :

group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

  1. K

  2. Mg

  3. Ni

  4. $I _{2}$

Show answer
Correct Option: D
Explanation:

Iodine's main role in animal biology is as constituents of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). These are made from addition condensation products of the amino acid tyrosine, and are stored prior to release in an iodine-containing protein called thyroglobulin. T4 and T3 contain four and three atoms of iodine per molecule, respectively. The thyroid gland actively absorbs iodine from the blood to make and release these hormones into the blood, actions which are regulated by a second hormone TSH from the pituitary. Thyroid hormones are phylogenetically very old molecules which are synthesized by most multicellular organisms, and which even have some effect on unicellular organisms.