Explore topic-wise InterviewSolutions in .

The correct choice is (d) 5 Seconds

To elaborate: The fire POINT is the lowest TEMPERATURE at which the vapour of OIL burns continuously for at least 5seconds when a small flame is brought near to it. The FLASH point means the at lowest temperature the oil GIVES enough vapour and flashes out is called flash point.

Correct choice is (d) Length of the CARBON CHAIN

Easy explanation: The saponification value also INDICATES the length of the carbon chain in the particular oil or fat. Higher the saponification value greater the PERCENTAGE of the short chain acids present in glycerides.

The correct answer is (b) Low

For explanation: The viscosity the most important and the only property of the lubricating oils to determine the thickness and velocity of the liquid. If the viscosity of an OIL is too low then it is IMPOSSIBLE to maintain liquid oil film between TWO moving or sliding liquids.so, every liquid must have good viscosity value.

The correct answer is (d) {(L -U)/(L-H)}*100

The BEST I can explain: The viscosity index can be GIVEN by {(L -U)/(L-H)}*100. Here, the U=viscosity at 100F OIL under the test. V=viscosity at 100F of standard coast oil having V.I zero. H=viscosity at 100F of pennsylvanian CRUDE oil having V.I 100

Correct answer is (c) EXTREME pressure lubrication

Explanation: Generation heat and friction are also takes place in extreme pressure lubrication. The thin lubrication is also CALLED as thin lubrication. At HIGH load and pressures, the contact between the SURFACES PRODUCES the more heat.

The CORRECT choice is (d) -40^oF

Easiest explanation: The MAXIMUM pour POINT REQUIREMENTS for REFRIGERATOR system is about -40^oF for lightest grade. For the heaviest grade the maximum pour point is about -13^oF.

The CORRECT option is (b) UNDESIRABLE

To explain I would say: Oxidation in the lubricating oils in undesirable because the insoluble product or sludge may clog the OIL holes, oil pipe lines, filters and the other parts of the lubricating SYSTEM.

The CORRECT option is (b) 3-3.35cm

For EXPLANATION I would say: In pour point experiment, the DIAMETER of the cylindrical tube is of the diameter is 3-3.35cm. The height of the CYLINDER is about 11.5-12.5cm. There is mark up to which the sample must be taken.

Correct CHOICE is (a) Nature of ALKALI

The explanation: The nature of alkali DECIDES the properties of the soap. The main characteristics of soap can be determined by nature of alkali USED in the HYDROLYSIS of the soap.

Right OPTION is (B) Mineral oils

For EXPLANATION: The castor oil, coconut oil and the ground nut oil are saponifiable. The mineral oils are not saponifiable. They are mixtures of hydrocarbons and do not react with KOH. So, they are not saponifiable.

Right choice is (d) 200

To EXPLAIN: The efflux of the redwood viscometer no2 is 200 seconds or LESS. Its jet for the outflow of the oil is having LARGER diameter. We can find the relative viscosities of the liquids using the redwood viscometer.

The correct option is (a) Too high

For explanation I would say: The excessive FRICTION takes place when the viscosity of the LUBRICATING oil is too high. As the viscosity is too high then the layers of the sliding liquids will be MOVING fast and OVERLAP on one another and causes the excess friction.

The correct ANSWER is (d) AREA of shaft

Explanation: The effectiveness of the hydro DYNAMIC lubrication does not depends upon the area of the shaft. The effectiveness mainly depends upon the design of bearing, load and SPEED of the shaft rotating.

The correct ANSWER is (a) 1000^oA

Easy explanation: In hydro dynamic lubrication, the sliding surfaces are SEPARATED COMPLETELY by applying a thin UNIFORM film of the lubricants between the TWO surfaces. The thickness of the lubricant film in the hydro dynamic lubrication is about 1000^oA.

The correct answer is (b) viscosity

To elaborate: The more friction of the greases is DUE to their viscosity. They are very thick SEMI solid lubricants. If the speed in high then friction is also high and then the heat PRODUCED will be more. As, the greases are very poor coolants they will be OVERHEATED.

Correct option is (B) False

For explanation I would say: The STATEMENT lamellar structure LUBRICANTS provide LUBRICATION is wrong because the non-lamellar lubricants also provide good lubrication. The lamellar structure is more likely to produce HIGH lubrication.

Right choice is (a) graphite

Explanation: For RAILWAY tracks, the lubricants USED are solid lubricants as they are exposed to SUN LIGHT and must bear the other CLIMATIC conditions.

The correct ANSWER is (a) Very high

Easy explanation: The saponification of VEGETABLE OIL and animal oil is very high. They are very high because it is difficult to hydrolyse them and require more AMOUNT of alkali for HYDROLYSIS.

Right ANSWER is (C) Vegetable OIL

Easy explanation: The vegetable oils and animal oils NEED LARGE amount of alkali to hydrolysis. They are the mixture of glyceryl and esters of fatty acids. Baby oil, liquid paraffin and liquid petroleum are the mineral oils and they are not saponifiable.

The correct option is (C) CRYSTALLIZED

To elaborate: On cooling below the pour point, the wax will be crystallized and the additive MOLECULES will protect them from crystallization as they will be adsorbed on the SURFACES of the CRYSTALS.

The correct option is (a) Linear POLYMERS

Explanation: The viscosity index can be improved by adding linear polymers like poly isobutyls and poly methacrylates and poly alkyl styrene. They range from 10000 to 100000 molecular WEIGHT. They INCREASE the viscosity and retains the original viscosity coefficient.

Right choice is (B) Very low

Explanation: The NEUTRALISATION values of the unblended petroleum OILS will be very low. The neutralisation values of the unblended petroleum oils ranges from 0.02 to 0.1. Values higher than this indicate faulty refining.

The correct ANSWER is (b) Oils and fats

The explanation is: SOAPS are MADE up of the chemical TREATMENT of the oils and fats by strong alkaline solution. The soap MOLECULE is the long non-polar tail which is hydrophobic end and the other is salt polar end which is the hydrophilic end.

Right answer is (d) long chain

Explanation: The molecular structure of the organic LUBRICANTS is in the form of long chains. The molecular chains are PARALLEL. The bonding strength between the molecules is very weak and MAY slide on each other.

The CORRECT option is (a) poor heat DISSIPATION

Best explanation: One of the disadvantages of the SOLID lubricants is poor heat dissipation. They have more ability to perform well at the high LOAD too(under high pressures).

Right answer is (a) 0.243mg

To explain I would SAY: To find out the acid VALUE of an oil we know the formula, acid value= (volume of KOH*N KOH*56)/wt of the oil in MG. Wt of the oil can be known by calculating the PRODUCT of density and volume to get 9.2gm. Substitute the values in formula to get 0.243mg as the answer.

Correct option is (d) 0.1

Explanation: The acid value of the LUBRICATING OILS must be always less than that of the 0.1. It is because the acid value changes the PROGRESS of the oxidation number and hydrolysis RATE and moisture content. BASED on which we have to replace the lubricating oil.

Right choice is (B) Increases

To explain I would say: The acid content will be increasing with time because as the time goes on the CHEMICAL reaction takes place and the number of H+ IONS increases with increase in time. So, the acid content ALSO increases with time.

Correct choice is (c) VISCOSITY index

Explanation: The RATE of the change of the viscosity with raise in temperature is measured by an arbitrary scale CALLED as viscosity index. The viscosity index is FOUND by comparing the viscosity of the OIL under the temperature of 1000F with two standard oils.

The CORRECT option is (a) MGS of KOH

Easiest explanation: Acid number of lubricating oil is defined as the mgs of KOH required to neutralise the all ACIDIC CONSTITUENTS of 1g of oil. So, it is also called as the NEUTRALISATION number.

The correct choice is (a) grease

Explanation: Grease is made from lubricating oil with metallic soaps or by adding solids like GRAPHITE, silica, talc etc. The petroleum oil they are not very SIMPLY lubricating oils, they are the lubricating oils thickener is DISPERSED to PRODUCE gel.

Right choice is (a) fatty ACIDS

Explanation: SOAPS are the metal salts of the fatty acids. Lithium, sodium, potassium and CALCIUM are the metal salts. SOAP molecules will be attached to SUBSTRATE surface of the soap lubricant.

The correct answer is (c) FLASH POINT

The EXPLANATION is: Pensky-Marten’s apparatus is used to find out the flash point of the lubricating oil at the TEMPERATURE in between the 80-3700C.

The CORRECT answer is (c) KOH

Explanation: In determination of the saponification value of the oil reaction, KOH is unreacted. The KOH is used as the catalyst and it remains unreacted and then titrated with STANDARD acid using PHENOLPHTHALEIN as an INDICATOR.

The correct answer is (d) Hard OIL

The EXPLANATION: Hard oil has no acid VALUE. COTTON seed oil has the acid value of 194-195. RAPE seed oil has low acid value that is about 1.4-4.0. The whale oil has the acidic value of 0.3-51.4.

Right option is (a) OXIDATION

For EXPLANATION I WOULD say: The darkening of the oil colour is due to the oxidation. On oxidation the formation of all soluble ALCOHOLS, ketones, acids and peroxides are PRODUCED. There by increasing the acid number, viscosity and darkening of the oil colour.

Correct ANSWER is (a) True

To explain I WOULD say: The COMPOUNDED oils are also called as BLENDED oils. The unblended oils have very less neutralisation number. It is about 0.02 to 0.1. The blended or compounded oils have very high neutralisation number.

The correct option is (d) Four

For explanation: The water bath is provided with a stirrer having four BLADES. It is provided with four blades because it HELPS to MAINTAIN the uniform temperature in bath to facilitate the uniform heating of the oil.

Correct option is (c) Heavy oil

For explanation I would SAY: Heavy oil is used as a lubricant in the machines that are operated at low SPEED under HIGH pressure. The heavy oil is used as it has resist the squeezing between the rubbing PARTS while operating the MACHINE.

Correct option is (a) Plastic INDUSTRY

The BEST I can EXPLAIN: The castor oil is mainly used for machinery at high speed and LOW pressure. It is used at plastic industry and medical purposes. For guns and SEWING machine the neats foot oil is used. For light machinery, whale oil is used.