Tag: petrochemicals and polymers

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Questions Related to petrochemicals and polymers

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

Determine the degree of association (polymerization) for the reaction in aqueous solution
$6HCHO\rightleftharpoons C _6H _{12}O _6$
If observed (mean) molar mass of HCHO and $C _6H _{12}O _6$ is $150$.

  1. $0.50$
  2. $0.833$
  3. $0.90$
  4. $0.96$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Let us consider the problem.
$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, 6HCHO \,\,\,\,\,\leftrightarrow {C _6}{H _{12}}{O _6}$
At equation $c\left( {1 - \alpha } \right)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\dfrac{{C\alpha }}{6}$
$\dfrac{{Observed\,moles\,concentration}}{{Initial\,moles\,concentration}} = \dfrac{{{M _\gamma }}}{{{M _0}}}$
$\dfrac{{C\left( {1 - \alpha } \right) + \dfrac{{C\alpha }}{6}}}{C} = \dfrac{{{M _\gamma }}}{{{M _0}}} = \dfrac{{30}}{{150}}$
Hence the answer is $\alpha  = 0.96$
Multiple choice chemistry polymer addition polymerisation types of polymerisation reactions petrochemicals and polymers

The monomer that undergo radical polymerisation most easily is ?

  1. $CH _2=CH _2$
  2. $C _6H _5CH=CH _2$
  3. $CH _2=C{(Me)} _2$
  4. $CH _3-CH=CH _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ethylene (CH2=CH2) is the simplest monomer and undergoes radical polymerization most readily because it lacks steric hindrance and has no substituents that would stabilize or destabilize the radical intermediate significantly compared to substituted monomers.

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

Which one of the following polymer is step-growth polymer

  1. Polythylene
  2. Nylon-$66$
  3. Buna-$S$ rubber

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

Step-growth polymers, often formed by condensation reactions between bifunctional monomers, include polymers like Nylon-6,6. Polyethylene, Buna-S rubber, and Orlon are chain-growth or addition polymers formed through radical or ionic mechanisms. Thus, Nylon-6,6 is the correct step-growth polymer.

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

Which of the following free radicals is the most stable ?

  1. primary

  2. methyl

  3. secondary

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

Electron poor species are stabilized by neighboring atoms that can donate electron density. The most common way to interpret rich neighbors here is the observation that increasing the number of alkyl groups on the carbon bearing the free radical increases its stability. 


Radical stability increases in the order methyl < primary < secondary < tertiary. 

Hence, option $D$ is correct.

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

Which of the following are used as free radical chain initiators ?

  1. Benzoyl peroxide

  2. di-tert-butyl peroxide

  3. Carbon tetrachloride

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

A radical initiator is a species that acts as the reactant of the initiation step of a radical chain reaction but does not participate in any of the propagation steps.
Radical initiators are substances that can produce radical species under mild conditions and promote radical reaction. These substances generally possess weak bonds that have small bond dissociation energy. Radical initiators are utilized in industrial processes such as polymer synthesis. Typical examples are halogen molecules, azo compounds and organic and inorganic peroxides such as Benzoyl peroxide, di- t-Butyl peroxide.

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

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

  1. PE

  2. HDPE

  3. LDPE

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

The polymers polyethene (PE), low density polyethene(LDPE), high density polyethene(HDPE) and teflon (polytetrafluoroethylene) can be made by free radical addition polymerisation (also known as chain growth polymerisation) mechanism.  To obtain free radicals, initiators such as benzoyl peroxide, tert-butyl peroxide or acetyl peroxide are used.

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

$\begin{bmatrix}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-\end{bmatrix} _n$

Polyvinyl alcohol (as shown above) is a unique polymer having high affinity for water. Which of the following procedures would be most suitable for its preparation?

  1. radical chain polymerisation of $CH _2=CH-CH _2-OH$
  2. radical chain polymerisation of $CH _2=CH-OH$
  3. radical chain polymerisation of $CH _2=CH-CO _2CH _3$, following by base catalysed hydrolysis
  4. radical chain polymerisation of $CH _2=CH-OCOCH _3$, followed by acid catalysed hydrolysis
  5. radical chain polymerisation of $CH _2=CH-OCOCH _3$, followed by base catalysed hydrolysis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\begin{bmatrix}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-\end{bmatrix} _n$ 


Polyvinyl alcohol is prepared by radical chain polymerisation of  $CH _2=CH-OCOCH _3$, followed by base catalysed hydrolysis in which acetate group is replaced by hydroxide group.