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Chemistry Test

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Which of the following terms describes the coordination of contiguous atoms of a ligand to a central atom?

  1. Hapticity

  2. Stacking

  3. Intercalation

  4. Denticity


Correct Option: A
Explanation:

The term hapticity is used to describe, how a group of contiguous atoms of a ligand are coordinated to a central atom. Hapticity of a ligand is indicated by the Greek character 'eta', η. A superscripted number following the η denotes the number of contiguous atoms of the ligand that are bound to the metal.

Which of the following process describes the exchange of ligands between two metal centers?

  1. Oxidative addition

  2. Beta-hydride elimination

  3. Transmetalation

  4. Carbometalation


Correct Option: C
Explanation:

Transmetalation is a general chemical reaction type in organometallic chemistry describing the exchange of ligands between two metal centers. The metal centers need not be the same. The ligands R and R' can be organic or inorganic. The double displacement reaction is conceptually related. Transmetalation is important in the synthesis of various organometallic compounds.

The acetic acid is manufactured by catalytic carbonylation of methanol through

  1. The Monsanto process

  2. The Shell higher olefin process

  3. Olefin metathesis

  4. Silylmetalation


Correct Option: A
Explanation:

The Monsanto process is an important method for the manufacture of acetic acid by catalytic carbonylation of methanol. This process operates at a pressure of 30-60 atm and a temperature of 150-200 °C and gives a selectivity greater than 99%.

A ligand is an ion, a molecule or a molecular group that binds to another chemical entity to form a larger complex. Among the following which one is characterised by a divalent organic ligand?

  1. Cyclopentadienyl complex

  2. Metallocene

  3. Sandwich compound

  4. Transition metal carbene


Correct Option: D
Explanation:

A transition metal carbene complex is a organometallic compound featuring a divalent organic ligand. The divalent organic ligand coordinated to the metal center is called a carbene. Carbene complexes for almost all transition metals have been reported.

Which among the following can also act as a bridging ligand?

  1. Fulminates

  2. Thiocyanate

  3. Cyanate

  4. Cyanide


Correct Option: C
Explanation:

The cyanate ion is an anion with the chemical formula written as [OCN] or [NCO]. In aqueous solution,  it acts as a base, forming isocyanic acid, HNCO. The cyanate ion is an ambidentate ligand, forming complexes with a metal ion in which either the nitrogen or oxygen atom may be the electron-pair donor. It can also act as a bridging ligand.

The carbides of the group 4, 5 and 6 transition metals except chromium are known as

  1. methanides

  2. molecular carbides

  3. intermediate transition metal carbides

  4. interstitial carbides


Correct Option: D
Explanation:

The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds.These carbides have metallic properties and are refractory. Some exhibit a range of stoichiometries, e.g. titanium carbide, TiC. Titanium carbide and tungsten carbide are important industrially and are used to coat metals in cutting tools.

Which among the following carbides is often simply called carbide?

  1. Aluminium carbide

  2. Tungsten carbide

  3. Silicon carbide

  4. Calcium carbide


Correct Option: B
Explanation:

Tungsten carbide (WC) is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine grey powder, but it can be pressed and formed into shapes for use in industrial machinery, tools, abrasives, as well as jewellry.

In which of the following sandwich compounds, the metals are bridged by a single carbocyclic ring?

  1. Monometallic half sandwich compounds

  2. Dimetallic half sandwich compounds

  3. Multidecker sandwiches

  4. Inverse sandwiches


Correct Option: D
Explanation:

In these anti-bimetallic compounds, the metals are found to be bridged by a single carbocyclic ring. Examples include {(THF)3Ca}2(1,3,5-triphenylbenzene) and {(Ar) Sn}2COT.

Alkali metals, alkaline earth metals and lanthanoid metals form ---------------------- carbides.

  1. salt-like

  2. acetylides

  3. sesqui

  4. covalent


Correct Option: B
Explanation:

Several carbides are assumed to be salts of the acetylide anion C22- (also called percarbide), which has a triple bond between the two carbon atoms. Alkali metals, alkaline earth metals, and lanthanoid metals form acetylides, e.g., sodium carbide Na2C2, calcium carbide CaC2, and LaC2 Lanthanoids also form acetylides with formula M2C3.

A carbene is a divalent organic ligand coordinated to the metal center. A carbene which can be likened to ketones is

  1. Difluorocarbene

  2. Fischer carbenes

  3. Schrock carbenes

  4. N-heterocyclic carbenes


Correct Option: B
Explanation:

Fischer carbenes can be likened to ketones, with the carbene carbon being electrophilic, much like the carbonyl carbon of a ketone. Like ketones, Fischer carbene species can undergo Aldol-like reactions. The hydrogen atoms attached to the carbon α to the carbene carbon are acidic, and can be deprotonated by a base such as n-butyllithium, to give a nucleophile which can undergo further reaction.

The force acting between molecules without permanent multipole moments is

  1. π-interactions

  2. London dispersion forces

  3. Van der Waals force

  4. Debye (induced dipole) force


Correct Option: B
Explanation:

London dispersion forces is a type of force acting between atoms and molecules.The LDF is a weak intermolecular force arising from quantum induced instantaneous polarization multipoles in molecules. They can therefore act between molecules without permanent multipole moments.

Which among the following results from the entire system's statistical tendency to increase its entropy?

  1. Dipole-dipole interactions

  2. Keesom interactions

  3. Hydrogen bonding

  4. Entropic force


Correct Option: D
Explanation:

An entropic force acting in a system is a phenomenological force resulting from the entire system's statistical tendency to increase its entropy, rather than from a particular underlying microscopic force.

The process of dehydration is associated with the formation of --------------------- bond.

  1. quintuple

  2. sextuple

  3. glycosidic

  4. peptide


Correct Option: D
Explanation:

A peptide bond (amide bond) is a covalent chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, causing the release of a molecule of water (H2O), hence the process is a dehydration synthesis reaction (also known as a condensation reaction), and usually occurs between amino acids.

Which of the following bonds is formed between a Lewis base & a Lewis acid ?

  1. Agostic bonds

  2. Bent bonds

  3. Dipolar bond

  4. π back bond


Correct Option: C
Explanation:

A dipolar bond, also known as dative covalent bond or coordinate bond is a kind of 2-centre, 2-electron covalent bond in which the two electrons derive from the same atom. Typically, a dipolar bond is formed when a Lewis base donates a pair of electrons to a Lewis acid.

Which among the following bonds is considered as an extension double bonds and triple bonds?

  1. Sigma bonds

  2. Pi bonds

  3. Delta bond

  4. Quadruple bond


Correct Option: D
Explanation:

A quadruple bond is a type of chemical bond between two atoms involving eight electrons. This bond is an extension of the more familiar types double bonds and triple bonds. Stable quadruple bonds are most common among the middle members transition metal elements such as rhenium, tungsten, molybdenum and chromium. Typically the ligands that support quadruple bonds are π-donors, not π-acceptors.

A sterically hindered molecule forms ----------------------- bonds.

  1. polar covalent

  2. coordinate covalent

  3. ionic

  4. bent


Correct Option: D
Explanation:

Bent bonds, also known as banana bonds, are bonds in strained or otherwise sterically hindered molecules whose binding orbitals are forced into a banana-like form. Bent bonds are often more susceptible to reactions than ordinary bonds.

The proton is spaced exactly halfway between two identical atoms in ----------------------.

  1. dihydrogen bond

  2. dihydrogen complexes

  3. low-barrier hydrogen bond

  4. symmetric hydrogen bond


Correct Option: D
Explanation:

A symmetric hydrogen bond is a special type of hydrogen bond in which the proton is spaced exactly halfway between two identical atoms. The strength of the bond to each of those atoms is equal. It is an example of a 3-center 4-electron bond. This type of bond is much stronger than normal hydrogen bonds, in fact, its strength is comparable to a covalent bond.

Which among the following is used to identify damage to the eye?

  1. Xylene cyanol

  2. Titan yellow

  3. Sudan II

  4. Rose Bengal


Correct Option: D
Explanation:

Rose Bengal is a stain. Its sodium salt is commonly used in eye drops to stain damaged conjunctival and corneal cells and thereby identify damage to the eye. The stain is also used in the preparation of Foraminifera for microscopic analysis.

The entropically unfavourable folded conformation of proteins gets stable by the formation of -------------------------- bonds.

  1. salt 

  2. cation-π interaction

  3. metallic 

  4. hydrogen 


Correct Option: A
Explanation:

Salt bond fall into the broader category of noncovalent interactions. A salt bond is actually a combination of two noncovalent interactions: hydrogen bonding and electrostatic interactions .This is most commonly observed to contribute stability to the entropically unfavourable folded conformation of proteins.

Which of the following dyes is used in histology for staining formulations ?

  1. Orange G

  2. Methyl red

  3. Methyl orange

  4. Martius yellow


Correct Option: A
Explanation:

Orange G or orange gelb is a synthetic azo dye used in histology in many staining formulations. It usually comes as a disodium salt. It has the appearance of orange crystals or powder.

The process of reversible inclusion of a molecule among the two other molecules is known as

  1. intercalation

  2. stacking

  3. conjugation

  4. aurophilicity


Correct Option: A
Explanation:

In chemistry, intercalation is the reversible inclusion of a molecule (or group) between two other molecules (or groups). Examples include DNA intercalation and graphite intercalation compounds.

Which of the following dyes can be used as a disinfectant?

  1. Yellow 2G

  2. Janus green B

  3. Crystal violet

  4. Fuchsine


Correct Option: D
Explanation:

Fuchsine or rosaniline hydrochloride is a magenta dye .It becomes magenta when dissolved in water; as a solid, it forms dark green crystals. As well as dying textiles, fuchsine is used to stain bacteria and sometimes as a disinfectant.

Paraffin wax is widely used on fruits and vegetables to make them shiny & to retard moisture loss and spoilage. It is an example of

  1. network covalent solids

  2. ionic solids

  3. metallic solids

  4. molecular solids


Correct Option: D
Explanation:

A classic molecular solid consists of small, non-polar covalent molecules, and is held together by London dispersion forces (van der Waals forces); a classic example is paraffin wax. These forces are weak, resulting in pairwise interatomic binding energies on the order of 1/100 those of covalent, ionic, and metallic bonds. Binding energies tend to increase with increasing molecular size and polarity.

An antiseptic is a substance that checks the growth & action of microorganisms especially in or on living tissue.The dye acting as a topical antiseptic is

  1. new fuchsine

  2. pararosaniline

  3. crystal violet

  4. congo red


Correct Option: C
Explanation:

Crystal violet i a triarylmethane dye. The dye is used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and is used as a topical antiseptic.

Which of the following is derived from the roots of plants of the madder genus ?

  1. Alizarin

  2. Red 2G

  3. Bismarck brown Y

  4. Alizarine Yellow R


Correct Option: A
Explanation:

Alizarin or 1,2-dihydroxyanthraquinone is an organic compound that is historically important as a prominent dye, originally derived from the roots of plants of the madder genus.

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