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Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

Earlier, gramophone records were made from a natural resin, shellac, which comes from insects on trees. Nowadays, records lighter in weight are made from synthetic plastics like:

  1. polyacrylonitrile

  2. PVC (or polyvinyl chloride)

  3. polythene

  4. bakelite
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

They are made from PVC (or polyvinylchloride) because they are hard and non-breakable.

Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

Which of the following polymers can be made by anionic addition polymerisation mechanism ?

  1. PVC

  2. PAN

  3. Telfon

  4. PP
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Anionic addition polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of vinyl monomers with strong electronegative groups. This polymerization is carried out through a carbanion active species. 


Like all chain-growth polymerizations, it takes place in three steps: chain initiation, chain propagation and chain termination. 

Characteristics: In order for polymerization to occur with vinyl monomers, the substituents on the double bond must be able to stabilize a negative charge. Stabilization occurs through delocalization of the negative charge. The delocalisation of electron density can be done by Electron withdrawing group such as $CN$, $-F$, $-Cl$ etc.
The solvent is determined by the reactivity of both the initiator and carbanion of the propagating chain end.

Hence, polymers that can be made by anionic addition polymerisation mechanism are PVC, PAN and Teflon.

Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

The main advantage of 'PVC' pipes for drainage is the feasibility of:

  1. mechanical laying

  2. physical laying

  3. chemical laying
  4. both $B$ and $C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

PVC pipes are lightweight, can be easily joined with solvents, and allow for fast mechanical installation using simple tools and fittings. This mechanical laying advantage is significant for drainage systems. Physical laying is not a standard term. Chemical laying is not relevant. The question focuses on the installation method advantage.

Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

Which of the following alkenes is most reactive towards cationic polymerization?

  1. ${ CH } _{ 2 }$ = ${ CHCH } _{ 3 }$
  2. ${ CH } _{ 2 }$ = $CHCl$
  3. ${ CH } _{ 2 }$ = ${ CHC } _{ 6 }{ H } _{ 5 }$
  4. ${ CH } _{ 2 }$ = ${ CHCOOCH } _{ 3 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In cationic polymerization the most stable cation will show the highest reactivity.

The order of reactivity will be-

$CH _2 = CH-C _6H _5 > CH _2  = CHCH _3 > CH _2 = CHCl >CH _2 = CHCOOCH _3$

Option C is correct.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

According to the law of triads :

  1. the properties of the middle element were in between those of the other two members.

  2. three elements arranged according to increasing weights have similar properties.

  3. the elements can be grouped in the groups of six elements.

  4. every third element resembles the first element in periodic table.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Dobereiner's law of triads, the properties of the middle element were in between those of the other two members. The elements were arranged in a group of three (called triads). The atomic weight of a middle element was almost the average of the other two. Three elements of the triad had similar chemical properties.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

The law of triad is applicable to a group of :

  1. $Cl, Br, I$
  2. $C, N, O$
  3. $Na, K, Rb$
  4. $H, O, N$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

For Dobereiner's triads, the atomic weight of middle element is almost average of other two. Thus, the law of triad is applicable to (1) $Cl, Br, I$ and (2) $C, N, O$. However, it is not applicable to (3) $Na, K, Rb$ and (4) $H, O, N$. 


(1) For $Cl, Br$ and $I$, $\displaystyle \dfrac {35.5+127}{2} = 81.25 \simeq 80$ 


(2) For $C, N, O$ $\displaystyle \dfrac {12+16}{2}=14$ 

(3) For $Na, K, Rb$ $\displaystyle \dfrac {23+85.5}{2}=54.25 \neq 39$ 

(4) For $H,O,N$ $\displaystyle \dfrac {1+14}{2}=7.5 \neq 14$

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Example of Dobereiner's triad is _________.

  1. $Li , Al , Ca$
  2. $Li , Na , K$
  3. $Li , K , Na$
  4. $K , Al , Ca$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Li,Na,K$ is the example of Dobereineer's traid. Here, average of atomic weights of  'Li' and 'K' equals atomic weight of 'Na'.


$\dfrac{Weight\ of\ Li+ weight\ of\ K}{2}$ =$\dfrac{7+39}{2}$ =$\dfrac{46}{2}$ =23


=weight of $Na$.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. Such an arrangement of elements called as :

  1. Dobereiner triad.

  2. Mendeleev triad.

  3. Modern triad.

  4. none of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dobereiner observed in few atoms that mass of one atom is equal to the average of two atoms. He defined almost all properties basing on atomic weight.Later on it was proved wrong any-ways. Hence, this is called Dobereiner triad. Lithium has 7, sodium has 23 where as potassium has 39 as atomic masses.
$ 23 = (7+39)/2 = 23$

Here, we could observe that sodium atomic mass is average of potassium and lithium masses.