Chemical Technology N6 — Document
April 2018 — N6 — Chemical Technology
N6
2018
Nated Engineering
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Q1— Section header —
1.1Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (1. 1. 1.
1.5\ the ANSWER BOOK.
1.1.1In a batch process, the rate of drying should be greatest at the end of the operation when water covers the entire surface of the solids.
1.1.2Free moisture content represents the amount of water that can be removed from dry solids under any given condition of air humidity and temperature.
1.1.3When part of the solid surface is no longer wetted by the liquid, the water area available for direct heat and mass transfer is regarded as the falling rate period.
1.1.4Freeze drying is the sublimation of water vapour from ice under high vacuum at temperature above 0 C.
1.1.5
1.2Define the following:
1.2.1Drying
1.2.2
1.3Discuss the principle of drying under the following heading
1.3.1Water on the surface
1.3
1.4Name TWO material that can be dried by EACH of the following dryer
1.4.1Tray dryer
1.4.2Rotary dryer
1.4.3
1.5Discuss the tray dryer under the following heading
1.5.1Advantages (2\
1.5.2Disadvantages (4\
1.5.3Draw and label diagram of a tray dryer. (10\
1.6State FOUR factors that influence the efficiency of the spray dryer (4\
1.7Differentiate between direct dryer and an indirect dryer (4\
Q2— Section header —
2.1Choose a term from COLUMN B that matches a description in COLUMN A. Write only the letter (A J\ next to the question number (2.1.1
2.1.5\in the ANSWER BOOK. COLUMN A COLUMN B
2.1.5The latent heat that is evolved when solid forms form a solution The results of mother liquor into the crystal face, which gives a milky surface and an impure product The number of new particles formed per unit time per unit
2.2Define the following
2.2.1Crystallisation
2.2.2
2.3Write brief notes on the following
2.3.1Equilibrium and yields (6\
2.3.2Homogeneous nucleation (5\
2.3.3Ostwald ripening (5\
2.4Give TWO methods obtained in laboratory experiments w he re crystals are usually produced from a solution (2\
2.5Give TWO factors that allow the purification of the product to be effective (2\
2.6Name THREE processes used to remove magma from the mother liquor during the puri fication of the product
2.7Name THREE groups of nucleation. (3\
2.8Give THREE advantages of crystallisation in the industr (3\
2.9
2.10Give ONE way in which initial breeding can be prevented (1\ [50]50
Q3— Section header —
3.1Give a suitable name o term for each of the following descriptions. Write only the name or the term next to the question number (3.1.1
3.1.5\in the ANSWER BOOK.
3.1.1The total kilograms of water vaporised in an evaporator per kilogram of original steam supplied
3.1.2The equilibrium vapour pressure which is exerted by the component in a liquid solution equals the mole fraction of that component in the solution times the equilibrium vapour pressure the component would
3.1.3The difference in temperature of the liquid at the heat source and the liquid at the top of the evaporating surface 15040106
3.1.4It occurs in all types of evaporators, and it is important when the solution to be evaporated contains dissolved materials that have an inverted solubility
3.1.5The carrying over of liquid droplets into a vapour space of an evaporator a carrying over that occurs because the vapour velocity is high enough to overcome the tendency for the liquid drops to settle
3.2Write brief notes on how the capacity varies according to the temperature of the feed
3.2.1When feed to the evaporator is at the boiling point
3.2.2When feed is cold
3.2.3
3.3Give THREE factors that influence the economy of an evaporator system (3\
3.4Write brief notes on the boiling point due to material in the solution (7\
3.5Discuss the gitated film evaporator under the following headings:
3.5.1Operation (6\
3.5.2Advantages (3\
3.5.3Disadvantages (3\
3.5.4Uses
3.6In making calculations dealing with evaporations, it is generally acceptable to make certain assumptions in order to simplify the work. Explain the assumption in an evaporator's calculation
Q4— Section header —
4.1Complete the following sentences by writing down only the missing word or words next to the question number (4.1.1 4.
1.10\the ANSWER BOOK. The c oncept of the film states that when a fluid is
4.1.2a thin film of the fluid is
4.1.3as existing between a (
4.1.4and a (
4.1.5The instantaneous
4.1.6through a
4.1.7by conduction is
4.1.8to the
4.1.9and to the
4.1.10
4.2Define the following
4.2.1Convection (3\
4.2.2Saturation air (4\
4.2.3Absorptivity (3\
4.2.4Wet bulb temperature (5\
4.2.5Dew point temperature 4\
4.3Write notes on the following
4.3.1Condensing vapour (6\
4.3.2Forced convection of gases (5\
4.4Discuss the general rule regarding the standard method for operating heat exchangers under the following heading
4.4.1Start up (4\
4.4.2Shut down (4\
4.4.3Steam condensate [50] TOTAL: 200 1504010650
Mark Allocation
Total200 marks
Sections50 + 50 + 50 = 150 marks
Paper information
TitleDocument
SubjectChemical Technology
LevelN6
Document typeQuestion paper
Year2018
MonthApril
Pages8
Downloads6
Examination context
Decade2010s
Years ago8y
SeasonAutumn (SH)
Start daySunday
Exam periodApril 2018
Days since exam3,113
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