Chemical Engineering Interview Questions and Answers
Question - 61 : - How Is Plate Heat Exchangers Used In An Ammonia Refrigeration System?
Answer - 61 : -
Plate heat exchangers are widely used in ammonia refrigeration systems, and they can be much smaller than the equivalent tubular exchanger can. They work best flooded. A flooded exchanger system needs a way to separate the liquid from the vapor. A typical system has a vessel, which acts as knockout drum, accumulator, and header tank in one, along with the heat exchanger. Liquid ammonia flows from the vessel to the exchanger, and liquid/vapor is returned to the middle of the drum. Vapor is removed from the top of the drum. The liquid/vapor mixture from the exchanger has a lower density than the liquid entering the exchanger, so gravity provides the driving force to circulate the refrigerant.
Question - 62 : - What Is An Effective Means Of Removing Silicon From Aluminum?
Answer - 62 : - Silicon is well known for its chemical inertness, (i.e. it tends not to react with many other chemicals). Depending on what type of silicon you are dealing with, this may or may not be easy to solve. If the silicon is from a lubricant, it is probably the graphitic form, which is soluble in a strong combination of nitric, and hydrofluoric acids, neither of which I would recommend for you to use...nor hydrofluoric acid is not easy to come by. If it is silicon from an acidic form (probably any other form other than a lubricant), you should try ammonia. In either case, leave your acetone at home...it will NEVER work! UPDATE: An ammonia solution worked very well in this case.
Question - 63 : - What Does The Catalystic Converter On An Automobile Really Do?
Answer - 63 : -
A catalytic converter is a device that uses a catalyst to convert three harmful compounds in automobile exhaust gas into harmless compounds. The three harmful compounds are:
Hydrocarbons (in the form of unburned gasoline)
Carbon monoxide (formed by the combustion of gasoline)
Nitrogen oxides (created when the heat in the engine forces nitrogen in the air to combine with oxygen).
Carbon monoxide is a poison for any air-breathing animal. Nitrogen oxides lead to smog and acid rain, and hydrocarbons produce smog. In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a muffler-like package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide. It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen.
Question - 64 : - Who Built The First Production Scale Pla (polylactic Acid) Facility?
Answer - 64 : -
The first production scale PLA (polylactic acid) facility was built by Cargill Dow in The Blair, Nebraska, and USA. The facility is designed to consume 40,000 bushels of corn per day and produce 300 million lb/year of PLA.
Question - 65 : - What Is The Largest Application For Surfactants?
Answer - 65 : -
The first production scale PLA (polylactic acid) facility was built by Cargill Dow in The Blair, Nebraska, and USA. The facility is designed to consume 40,000 bushels of corn per day and produce 300 million lb/year of PLA.
Question - 66 : - How Can You Separate Hydrogen Peroxide Into Hydrogen And Oxygen?
Answer - 66 : -
This is easily done. Just expose hydrogen peroxide to air. The oxygen in the air will oxidize the hydrogen peroxide into its component gases. It happens far too slowly for industrial or most other purposes (an enzyme catalyst can be used to speed up the process). However, neither hydrogen nor oxygen is produced in this manner in industry. The enzyme catalyst is called "catalase".
Question - 67 : - What Is A Solvent?
Answer - 67 : -
According to the US Solvent Council, "A solvent is a liquid which has the ability to dissolve, suspend, or extract other materials without chemical change to the material or solvent. Solvents make it possible to process, apply, clean, or separate materials.
Question - 68 : - What Is The Easiest Way To Extract Hydrogen From Water And The Safest Way To Store It?
Answer - 68 : -
Electrolysis (which means splitting using electricity) of water is the method for producing hydrogen from water. The safest way to commercially store it would be to use a palladium "sponge", because palladium adsorbs several hundred times it's own volume in hydrogen. One would need to produce a compound with a very high surface area, which has a thin coating of palladium. This type of material is commonly used as a catalyst in chemical processes.
Question - 69 : - What Are The Three Classes Of Organic Solvents?
Answer - 69 : -
Typically, organic solvents can be split up in the following classes: Oxygenated, Hydrocarbon, and Halogenated. Oxygenated solvents include alcohols, glycol ethers, ketones, esters, and glycol ether esters. Hydrocarbon solvents include aliphatics and aromatics. Halogenated solvents include those that are chlorinated primarily.
Question - 70 : - What Is Happening When Paint Dries?
Answer - 70 : -
During the manufacture of paint, solvents are added to make the paint thinner so that it can be applied to various surfaces. Once the paint is applied, the solvents evaporate and the resins and pigments that make up the paint for a thin, solid layer on the surface.