Interview Questions.

Question 1. What Are Some Of The Polymers That You Encounter Every Day? Describe Their Physical Properties.

Answer :

Sandwich baggage, carpets, nylon stockings, stackable chains, milk cartons, and so forth.

 

Question 2. Why Do Different Polymers Have Different Properties?

Answer :

They have exclusive chemical compositions (different monomer gadgets), distinctive systems, one of a kind approaches of being fabricated, and many others.

Chemical Interview Questions
Question three. Why Are Olefins (alkenes) Good Monomers For Polymerization Reactions?

Answer :

The electrons within the vulnerable p-bonds may be used to form strong s bonds to other monomer gadgets.

 

Question four. What Kinds Of Structural Changes Accompany Bond-breaking And Bond-forming In Olefin Polymerization?

Answer :

The olefin monomers are flat (two-dimensional) molecules with sp2-hybridized carbon atoms. The polymers are 3-dimensional molecules wherein the carbon atoms are sp3 hybridized.

Question five. Examine Samples Of Ldpe (sandwich Bag, Squeeze Bottle) And Hdpe (milk Jug, Grocery Bag). What Are Some Of The Differences In The Physical Properties Of These Substances?

Answer :

LDPE – more transparent, flexible, waxy.
HDPE – more opaque, rigid, non-waxy.
 

BioChemistry Interview Questions
Question 6. How Does The Molecular-degree Structure Of These Polymers Influence Their Physical Properties?

Answer :

The structure (e.G., volume of branching) determines how the man or woman polymer molecules can orient (or "percent") within the stable kingdom. This, in flip, impacts physical houses such as density, crystallinity, melting factor, and electricity.

Question 7. How Can Chemists Control Which Type Of Polyethylene (ldpe Vs. Hdpe) Is Generated?

Answer :

Through the choice of appropriate catalysts and response situations.

Analytical Chemistry Interview Questions
Question 8. Besides The Extent Of Branching, Can You Think Of Any Other Structural Parameters That Might Lead To Differences In Physical Properties?

Answer :

The average fee of n (the quantity of monomer units within the polymer) and the variety in person values of n.

Question nine. Does Ethylene Polymerize Under Mild Conditions In The Absence Of A Catalyst?

Answer :

No, within the absence of a catalyst, ethylene molecules would want to collide at very high energy so as to react with each different.

Quality Control Chemist Interview Questions
Question 10. What Is The Role Of A Catalyst?

Answer :

A catalyst reduces the electricity of activation for a response via presenting an alternative pathway. In this manner, it hurries up the reaction and permits it to proceed below milder conditions.

Question eleven. Why Are Metals Often Good Catalysts?

Answer :

They provide a site in which natural molecules can come together and react.

Chemical Engineering Interview Questions
Question 12. What Is The Difference Between A Heterogeneous And A Homogeneous Catalyst? What Are Some Of The Advantages Of Homogeneous Catalysts?

Answer :

Heterogeneous catalysts are insoluble inside the response medium, while homogeneous catalysts are soluble. Since homogeneous catalysts are generally molecular species, they're extra amenable to examine the use of the spectroscopic tools of chemistry. In addition, they can be chemically modified or "tailor-made" to produce polymers with a selected form of shape.

Chemical Interview Questions
Question thirteen. How Would You Describe The Orientation Of The Ligands Around The Zr Center In The Homogeneous Zirconium Catalyst?

Answer :

The ligands – the two cp's, the alkyl group, and the olefin (or open website) – are oriented in a tetrahedral fashion round Zr.

Question 14. What Is The Nature Of The Bonding Interaction Between A Metal And An Olefin?

Answer :

The olefin makes use of the electrons in its p-bond to interact with the metal.

Question 15. Polymer Chain Growth Can Be Terminated By B-hydride Elimination Or By Reaction With H2. What Is One Advantage Of The H2 Reaction?

Answer :

It lets in the chemist to forestall chain growth at a preferred stage, rather than relying on the "herbal" technique of b-hydride elimination. Hence, it offers the chemist some control over the value of n.

Organic Chemistry Interview Questions
Question 16. What Are The Other Ways In Which Chemists Can Manipulate The Properties Of Polymers?

Answer :

By the use of one of a kind monomers. For example, the incorporation of a phenyl (C6H5) unit into the monomer leads to polystyrene, at the same time as the incorporation of a chloro (Cl) organization results in PVC, a polymer with very distinct residences.
By the use of different fabrication strategies. For example, polystyrene can be glassy or foamy relying on how it is fabricated.
Question 17. "co-polymers" Consist Of Two Different Monomers ("a" And "b") Joined In An Alternating Fashion (ababab...). Block Co-polymers Also Consist Of Two Different Monomers, But In This Case Blocks Of Polymer Containing Only A Units Are Joined To Blocks Of Polymer Containing Only B Units (aaaaabbbbb...). How Might Block Co-polymers Be Synthesized?

Answer :

After the polymerization has been allowed to continue with monomer A, the olefin feedstock is modified to B and the polymerization continues.

Chemistry Interview Questions
Question 18. A Polymer's Structure Influences Its Physical Properties. Describe Two Structural Variations That Are Possible For Polypropylene But Not For Polyethylene.

Answer :

The orientation of the monomer devices alongside the chain (head-to-tail, head-to-head, random) and the orientation of the methyl corporations with recognize to the polymer backbone (tacticity).

BioChemistry Interview Questions
Question 19. Consider The Polymerization Of Vinylidene Chloride, Ch2=ccl2. What Structural Variations Are Possible In Poly(vinylidene Chloride)?

Answer :

Orientation of the monomer units alongside the chain.

Question 20. Consider The Polymerization Of 1,2-dichloroethylene, H(cl)c=c(cl)h. What Structural Variations Are Possible In Poly(1,2-dichloroethylene)?

Answer :

Tacticity.

Chemical reaction Interview Questions
Question 21. Head-to-tail Polymerization Of Propylene Is Observed With The [cp2zr(r)]+ Catalyst. Explain This Result On The Basis Of Molecular-stage Interactions.

Answer :

Each incoming propylene molecular orients with its methyl institution in toward R, in place of out towards cp, on the way to keep away from unfavourable contacts with the bulky cp's. When the R institution migrates to propylene, it migrates to the nearer olefinic carbon, which is always the one bearing the methyl organization (the "b carbon").

Question 22. Atactic Polypropylene Is Always Produced With The [cp2zr(r)]+ Catalyst. Explain This On The Basis Of Molecular-level Interactions.

Answer :

There is no choice for the methyl institution on propylene to be oriented up or down, because in each case it has exactly the identical interaction with a cp organization. Since there is no up/down choice, a random (atactic) orientation of methyls alongside the chain effects.

 

Question 23. What Does It Mean For A Molecule Or A Ligand To Be "chiral"? What Properties Does Chirality Impart To A Molecule?

Answer :

Molecules that aren't superimposible on their mirror photographs are chiral. Mirror photo isomers are known as enantiomers. Enantiomers have same bodily residences except that they rotate plane polarized light in contrary guidelines.

Question 24. Explain What Is Meant By "c2 Symmetry" And "mirror Plane Symmetry". Can A Molecule With "reflect Plane Symmetry" Ever Be Chiral?

Answer :

"C2 symmetry" means that 180o rotation approximately an axis thru the molecule effects in a geometry equal to the starting geometry. "Mirror plane symmetry" method that one half of the molecule can be perfectly meditated into the opposite 1/2 via a symmetry plane. Molecules with mirror aircraft symmetry can not be chiral.

Analytical Chemistry Interview Questions
Question 25. Consider A Homogeneous Zirconium Catalyst In Which Two Cyclopentadienyl Ligands Are Connected By A —ch2–ch2— Bridge. Which Symmetry Elements Does The (bridged-cp2)zr Moiety Possess? What Is The Expected Tacticity Of The Polypropylene Produced Using This Type Of Catalyst? Why?

Answer :

The (bridged-cp2)Zr moiety possesses each C2Zr catalyst discussed in Session 5, it might be anticipated to produce atactic polypropylene, for the reason that methyl organization on the propylene could don't have any up/down choice.