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Chemistry Test

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Which of the following organometallic compounds acts as a co-catalyst for olefin polymerizations of the Ziegler-Natta type?

  1. Trimethylgallium

  2. Trimethylindium

  3. Trimethylaluminium

  4. Methylaluminoxane


Correct Option: D
Explanation:

Methylaluminoxane, is pyrophoric, and is violently reactive with any chemical bearing an acidic proton. However, it is generally used as a solution in an (aromatic) hydrocarbon due to its relatively high solubility in such hydrocarbons.It is most well known for being a co-catalyst for olefin polymerizations of the Ziegler-Natta type.

The organometallic compound which can be alloyed with III-V materials is

  1. Aluminium arsenide

  2. Aluminium nitride

  3. Aluminium antimonide

  4. Indium antimonide


Correct Option: C
Explanation:

Aluminium antimonide (AlSb) is a semiconductor of the group III-V family containing aluminium and antimony. The lattice constant is 0.61 nm. The indirect bandgap is approximately 1.6 eV at 300 K, whereas the direct band gap is 2.22 eV. It can be alloyed with other III-V materials to produce the following ternary materials: AlInSb, AlGaSb and AlAsSb.

Which of the following process is used to produce acetic acid by catalytic carbonylation of methanol?

  1. The Monsanto process

  2. The Shell higher olefin process

  3. Olefin metathesis

  4. Alkane metathesis


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%.

Pseudo-pericyclic reactions are reactions that appear at first glance to be pericyclic.Which of the following reaction is 'pseudo' pericyclic?

  1. Transmetalation

  2. Carbometalation

  3. Hydrometalation

  4. Alkyne trimerisation


Correct Option: D
Explanation:

An alkyne trimerisation reaction is a 2+2+2 cyclisation reaction in which three alkyne molecules react to form an aromatic compound. The reaction is 'pseudo' pericyclic since it has not been observed to occur without the assistance of metal catalysis; and the metal catalyst assembles the ring stepwise via intermediates which are not directly in between (in a geometric sense) the starting material and products.

Among the following compounds which one is commonly found as Grignard reagents?

  1. Organocopper compounds

  2. Organolithium compound

  3. Organoaluminium compounds

  4. Organomagnesium compounds


Correct Option: D
Explanation:

Organomagnesium compounds are widespread. They are commonly found as Grignard reagents. The formation of alkyl or aryl magnesium halides (RMgX) from magnesium metal and an alkyl halide is attributed to a SET process. Examples of Grignards are phenylmagnesium bromide and ethylmagnesium bromide.

Sapphire is a gemstone, commonly worn as jewellery.The layers of ------------------- compound can be grown on sapphire.

  1. aluminium phosphide

  2. aluminium gallium arsenide

  3. aluminium gallium nitride

  4. gallium nitride


Correct Option: C
Explanation:

Aluminium gallium nitride (AlGaN) is a semiconductor material. It is an alloy of aluminium nitride and gallium nitride. AlGaN is used to manufacture light-emitting diodes operating in blue to ultraviolet region, where wavelengths down to 250 nm (far UV) were achieved. It is also used in blue semiconductor lasers. AlGaN layers can be also grown on sapphire.

Which of the following casting process, the molten metal is forced under high pressure into a mold cavity?

  1. Sand casting

  2. Investment casting

  3. Die casting

  4. Continuous casting


Correct Option: C
Explanation:

Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.

Among the following which one acts as a reservoir in metal casting mold to prevent cavities due to shrinkage?

  1. Pattern

  2. Flask

  3. Core

  4. Riser


Correct Option: D
Explanation:

A riser, also known as a feeder, is a reservoir built into a metal casting mold to prevent cavities due to shrinkage. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify.

Sulphide ores are generally concentrated by

  1. Hydraulic washing

  2. Electro magnetic separation

  3. Froth floatation process

  4. Chemical Method


Correct Option: C
Explanation:

This process is generally used for the concentration of sulphide ores. In this method the ore is taken in an iron tank along with a mixture of water and pine oil. The mixture is vigorously agitated by blowing compressed air. The oil forms a froth with air. The metallic ore particles get stick to the forth and rise to the surface as scum.The impurities are wetted by water and will settle down at the bottom .The froth containing the metallic ore particles is skimmed off and dried.

Which of the following is not a true equilibrium constant?

  1. An acid dissociation constant

  2. The binding constant

  3. A dissociation constant

  4. Conditional constants


Correct Option: D
Explanation:

Conditional constants, also known as apparent constants, are concentration quotients which are not true equilibrium constants but can be derived from them. A very common instance is where pH is fixed at a particular value.

Which compound is used in infrared detectors, infrared LED's and lasers?

  1. Gallium antimonide

  2. Gallium arsenide

  3. Antimony trioxide

  4. Aluminium oxide


Correct Option: A
Explanation:

Gallium antimonide (GaSb) is a semiconducting compound of gallium and antimony of the III-V family. It has a lattice constant of about 0.61 nm. GaSb can be used for infrared detectors, infrared LED's, lasers,  transistors and thermophotovoltaic systems.

The two dissimilar metals are bonded with the process of

  1. Casting

  2. Forging

  3. Rolling

  4. Cladding


Correct Option: D
Explanation:

Cladding is the bonding together of dissimilar metals. It is distinct from welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure.

Which of the following processes isa modified die casting process ?

  1. Continuous casting

  2. Centrifugal casting

  3. Semi-solid metal

  4. Spin casting


Correct Option: C
Explanation:

Semi-solid metal (SSM) casting is a modified die casting process that reduces or eliminates the residual porosity present in most die castings. Rather than using liquid metal as the feed material, SSM casting uses a higher viscosity feed material that is partially solid and partially liquid.

The gases generated during the pour escapes through

  1. Sprue

  2. Gates

  3. Draft

  4. Vents


Correct Option: D
Explanation:

Vents are the additional channels that provide an escape for gases generated during the pour. 

Which among the following is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action?

  1. Brazing

  2. Soldering

  3. Punching

  4. Spinning


Correct Option: A
Explanation:

Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux.

Which among the following compouds is not a protein?

  1. Collagen

  2. Elastin

  3. Pikachurin

  4. Tubulin


Correct Option: C
Explanation:

Pikachurin is a polysaccharide that in humans is encoded by the EGFLAM gene.Pikachurin is a dystroglycan-interacting polysaccharide which has an essential role in the precise interactions between the photoreceptor ribbon synapse and the bipolar dendrites.

The process of purification of impure metals by removing metallic and nonmetallic impurities is known as refining of metals. The volatile metals like mercury, zinc and cadmium are refined by

  1. Poling

  2. Liquation

  3. Distillation

  4. Oxidation


Correct Option: C
Explanation:

This process is employed for purification of volatile metals like mercury, zinc and cadmium. The impure metal is heated in a retort and its vapours are separately condensed in a receiver. While the pure metal distills over, the non-volatile impurities are left behind in the retort.

The central nervous system controls the voluntary muscle contraction .The metal necessary for the contraction of muscles is

  1. Iron

  2. Sodium

  3. Zinc

  4. Copper


Correct Option: B
Explanation:

Sodium and potassium are necessary for the electrical activities of the nerves and for the contraction of muscles.

Straight lines and relatively large radius curves are cut by ------------------------ shears.

  1. throatless

  2. power

  3. bench

  4. alligator


Correct Option: B
Explanation:

A power shear is electrically or pneumatically powered hand tool designed to blank large pieces of sheet metal. They are designed to cut straight lines and relatively large radius curves. They are adventageous over a bandsaw because there is not a size limit. Large versions can cut sheet metal up to 12 gauge.

The objects of a fixed cross-sectional profile are created by the process of

  1. Extrusion

  2. Shear forming

  3. Sintering

  4. Fabrication


Correct Option: A
Explanation:

Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses.

Which of the following brazing is a materials joining technique ?

  1. Vacuum brazing

  2. Silver brazing

  3. Furnace brazing

  4. Torch brazing


Correct Option: A
Explanation:

Vacuum brazing is a materials joining technique that offers significant advantages: extremely clean, superior, flux-free braze joints of high integrity and strength. The process can be expensive because it must be performed inside a vacuum chamber vessel. Temperature uniformity is maintained on the work piece when heating in a vacuum, greatly reducing residual stresses due to slow heating and cooling cycles.

Microtubules are fibrous, hollow rods, that function primarily to help support and shape the cell. The proteins stablising the microtubules is

  1. Myosin

  2. Spectrin

  3. Tau proteins

  4. Cadherins


Correct Option: C
Explanation:

Tau proteins are proteins that stabilize microtubules. They are abundant in neurons in the central nervous system and are less common elsewhere. When tau proteins are defective, and no longer stabilize microtubules properly, they can result in dementias such as Alzheimer's disease.

Among the following proteins which one is the key structural component of hair and nails?

  1. Actin

  2. Coronin

  3. Dystrophin

  4. Keratin


Correct Option: D
Explanation:

Keratin refers to a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails.

In which of the following casting process the expanded polystyrene foam pattern are used?

  1. Investment casting

  2. Evaporative-pattern casting

  3. Lost-foam casting

  4. Full-mold casting


Correct Option: D
Explanation:

Full-mold casting is an evaporative-pattern casting process which is a combination of sand casting and lost-foam casting. It uses a expanded polystyrene foam pattern which is then surrounded by sand, much like sand casting. The metal is then poured directly into the mold, which vapourizes the foam upon contact.

A hollow casting or hollow cast is created in --------------------- casting.

  1. non-expendable mold

  2. permanent mold

  3. slush

  4. vacuum permanent mold


Correct Option: C
Explanation:

Slush casting is a variant of permanent molding casting to create a hollow casting or hollow cast. In the process the material is poured into the mold and allowed to cool until a shell of material forms in the mold. The remaining liquid is then poured out to leave a hollow shell. The resulting casting has good surface detail but the wall thickness can vary. The process is usually used to cast ornamental products, such as candlesticks, lamp bases and statuary from low-melting-point materials.

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