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Industrial chem Flashcards

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1
Q

How N2 become nitrate?

A

lightning–> N2 combines with oxygen –> NO2 –> dissolve in water to give nitrates

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2
Q

effect of catalyst

A

increase rate of reaction by providing an alternative pathway with lower activation energy

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3
Q

why NH3 is removed from catalytic chamber before eqm

A
  1. it takes a long time to reach eqm

2. to increase total amount of NH3 produced per unit time

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4
Q

why methanol is important

A

act as a starting material to make organic compounds with larger carbon numbers.

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5
Q

advancement of methanol production technology

A

conversion of biomass to syngas for methanol production –> renewable feed stocks

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6
Q

why the initial rate is used

A

initial concentration is known

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7
Q

maxwell boltzmann distribution curve axis

A 
x = molecular kinetic energy
y = fraction of molecules
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8
Q

activation energy unit

A

kJ per mole

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9
Q

how to produce Cl2 and NaOH

A

electrolysis of brine in flowing mercury cell

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10
Q

the difference in yield and atom economy

A

atom economy is based on a 100% completed reaction
yield is related to the extent of reaction
High atom economy =/= high yield

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11
Q

definition of activation energy

A

minimum energy possessed by the colliding reactant particles in order that a reaction can occur

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12
Q

why produce Vitamin C industrially

A

solve the problem of inadequate supply of vitamin C

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13
Q

definition of initial rate

A

instantaneous rate at the start of a reaction

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14
Q

from graph–> order of reaction w.r.t. (X) =1?

A

a straight line passing through the origin
directly proportional to (X)
order of reaction w.r.t. (X) =1

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15
Q

why use natural gas in Haber process

A

natural gas remains the more cheaper way to provide hydrogen as feedstock for the production of ammonia in the Haber process

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16
Q

How to increase the yield in Haber process without changing the temp/pressure

A

remove the ammonia from the production mixture

eqm position to the product side

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17
Q

why catalyst needs to be replaced

A

catalyst can be poisoned

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18
Q

where to locate chloralkali industry

A

near the sea because easy to get raw materials

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19
Q

mercury is…

A

poisonous

toxic not sure

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20
Q

chlorine gas is….

A

poisonous

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21
Q

why heat exchanger is used

A
  1. the hot gas from reaction chamber can help heat up hydrogen and nitrogen
  2. to save energy by conserving energy
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22
Q

HCl is…

A

irritating

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23
Q

enzyme is

A
  1. provide catalyst

2. biodegradable

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24
Q

why reactants need to be purified if there is catalyst

A

impurities in the reaction mixture may poison the catalyst

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25
Q

raw material of manufacturing vitamin C

A

glucose

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26
Q

methanol to acetic acid

A

carbonylation

CH3OH + CO -(HI)–> CH3COOH

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27
Q

how NaOH is obtained form membrane cell

A
  1. use brine as electrolyte
  2. membrane is permeable to cations but not anion
  3. NaOH is obtained in the cathode compartment
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28
Q

high pressure -ve impact

A

high construction cost

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29
Q

what is window cleansing agent made of

A

dilute ammonia

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30
Q

why there is a distribution of kinetic energy of the oxygen molecules

A

The motion of gas molecules is random
It follows that the collisions between molecules also occur randomly.
Some collision result in a gain in KE for one molecule and a loss of KE for the other.

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31
Q

uses of methanol in everyday life

A

fuel and solvent

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32
Q

what is green chemistry

A

Green chemistry is a chemical technology that encourages the design of products and processes that reduce the use and generation of hazardous substances.

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33
Q

uses of ethanoic acid in industry

A

to make vinegar for food pickling

to make esters which are used as artificial flavorings and solvents for paints and inks.

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34
Q

source of dioxin

A

combustion of PVC

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35
Q

why an increase in temperature can lead to an increase in the reaction rate

A

An increase in temperature will increase the average KE of the molecules
This will increase the collision frequency and result in greater effective collisions among molecules
There is a larger portion of molecules will have KE greater than activation energy.

36
Q

is a reaction with high atom economy means that it also has a high yield?

A

no
The calculation of atom economy is based on a 100% completed reaction. Most reactions do not go to completion and the yield is related to the extent of reaction
Thus a reaction with high atom economy does not necessarily have a high yield.

37
Q

what is the use of the membrane in membrane cell

A

The membrane is permeable to cations but not anions

NaOH solution is obtained in the cathode compartment

38
Q

advantages of membrane cell overflowing mercury cell

A

no poisonous mercury
less energy required
less maintenance

39
Q

why no solvent is greener

A

less solvent emit to the environment

40
Q

advantage of using flowing mercury cell

A

high purity of hydrogen gas and chlorine gas produced

41
Q

disadvantage of using flowing mercury cell

A

poisonous mercury may pollute the environment

42
Q

why we cant simply use air as a source of N2

A

air contains O2
O2+ H2 –> explosion

and poison the catalyst

43
Q

what is the purpose for using a drier in dealing with N2 and H2

A

to prevent water making Fe (the catalyst) to turn to Fe3O4 (poisoned)

any impurities present would poison the catalyst

44
Q

what is the use of heat exchanger

A

the heat evolved from the haber process can be used to heat up the reactant gases before passing into the reaction chamber using the heat exchanger

45
Q

why V2O5 instead of Pt is used in contact process

A

cheaper

less likely to be poisoned than Pt

46
Q

how to say the rate 八倍 in english

A

the rate increases by a factor of 8

47
Q

in a reaction of A+B+C to D

how to keep conc. of B and C constant

A

(B) (C)&raquo_space;»>(A)

so the rate only depends on concentration of A

48
Q

what does second order mean

A

the rate is directly proportional to the square of concentration of the reactant

49
Q

what is the change of color of end pt of reaction between MnO4 and H2O2

A

from colorless to pink

50
Q

why should we add a small fixed amount of S2O32- to the reaction mixture

A

allow to find the rate of reaction by measuring the time needed for formation of the same amount of I2

smaller % error as larger time difference between experiment

51
Q

why should we add starch to signal the finishing point of the iodine clock reaction even though I2 has a color itself

A

if no starch
the color change will be colorless to pale yellow then yellow then brown
not obvious to be observed

52
Q

explain collision theory

A

for a chemical reaction to occur, the reactants must have sufficient amount of energy and collide in the right direction

53
Q

what is first order reaction

A

the rate of reaction is directly proportional to the concentration of the reactant

54
Q

outline what measurements have to be taken in order to determine the activation energy of a reaction

A

keeping the initial concentration of the reagent unchanged
carry out the experiment at different temperatures
determine the corresponding initial rate (k constant)
plot a graph of log k against 1/T
slope of the graph = -Ea/2.3R

55
Q

what is activated complex

A

a highly unstable species at the maximum potential energy

it cannot be detected or isolated

56
Q

which step is the rate-determining step

A

the step with the largest activation energy

slowest

57
Q

if the rate determining step include intermediate

should we include that in the rate equation?

A

NOOOO

use the reactant that produces the intermediate to be included in the reaction

58
Q

what does rate of reaction means

A

the rate of change in concentration of reactant or products

59
Q

what does the overall order of a reaction means

A

the sum of powers to which the concentration are raised in the rate equation

60
Q

why catatlyst need frequent replacement

A

they may be poisoned
they may react with impurities
the surface is covered with impurities

61
Q

why the reaction rate of the equation 2I- + S2O82- is slow

A

due to the repulsion between the two negatively charged reactions
so it has a high activation energy

62
Q

advantage of using catalyst in industrial process

A

the desired percentage of conversion can be reached in a much shorter time
reactions can be carried out at much lower temperatures to save energy
reduce the formation of side products

63
Q

what is fermentation

A

it is the breaking down of large carbohydrate molecules into smaller molecules by the action of microorganisms in the absence of air

why cant there be air?
O2 will oxidize ethanol to acid

64
Q

advantage of using enzymes in industrial process

A

they work at low temperature and thus save energy
can control them easily and stop them working by changing the temperature or pH
they are biodegradable and does not cause environmental problems
they operate in mild conditions

65
Q

what is the procedure of industrial process

A

raw materials to feedstocks to synthetic products

66
Q

advantage of petrochemistry

A

large scale of production leads to cheaper product

boost the economy of the society by increasing profit and job opportunities and infrastructure

67
Q

disadvantage of petrochemistry

A

natural resources are limited and non-renewable

pollution of all types has negative impacts on the environment

68
Q

why shouldnt we obtain vitamin C from natural sources

A

the extraction cost is high and the supply cannot meet the worldwide demand
the yield of plant crops is declining due to the climate change.
it is not economical to grow plants simply for a supply of Vitamin C because it is time-consuming and the yield is not satisfactory

69
Q

what are the name of the two process of manufacturing Vitamin C

A

older: Reichstein
newer: two-step fermentation process (better)

70
Q

why two-step fermentation process is better than Reichstein process

A

it uses less toxic solvents and reagents so it is more environmentally friendly
its overall cost is lower

71
Q

why plants need N

A

to produce amino acid

72
Q

what can be used to dry NH3

A

CaO

73
Q

NH4NO3 is….

A

explosive

74
Q

disadvantage of using fertilizers

A

growth of algae which float on water and cut off sunlight from the plants below

75
Q

why farmers do not prefer using NH3 as a fertilizer

A

it has a pungent bad smell
it makes the soil too alkaline
it is difficult to transport

76
Q

why ammonia solution is used in window cleaners

A

ammonia solution is alkaline and can assist the hydrolysis of oily dirt to form soluble compounds

77
Q

why using ammonia solution instead of NaOH solution in window cleaner

A

sodium hydroxide is corrosive to skin

ammonia is volatile

78
Q

how atmospheric nitrogen can be converted to nitrates in soil

A

during lightning, nitrogen combines with oxygen to give nitrogen oxides
Nitrogen oxide dissolves in rainwater to give nitrates

79
Q

how nitrogen in animal protein can return to soil

A

excretion of animals contain urea which is a soluble nitrogen compound

80
Q

what are the potential hazard of bleach

A

it is irritating, toxic and corrosive

81
Q

what is the special characteristics of membrane cell

A

the membrane only allow Na+ to pass through to complete the circuit and it prevent mixing of Cl2 with H2
also NaOH obtained is pure and does not mix with NaCl

82
Q

importance of methanol

A

as a feedstock to make a wide variety of other chemicals

as a solvent

83
Q

what is green chemistry

A

it is the utilisation of a set of principles to design and apply chemical processes that maximize the production efficiency, but at the same time, reduce or eliminate the use and generation of hazardous substances

84
Q

what is sustainable development

A

it is the development which meets the needs of the present without compromising the ability of future generations to meet their own need

85
Q

12 principle of green chemistry

A 
waste prevention
maximise atom economy
avoid hazardous chemcial syntheses
design safer chemicals
avoid auxiliary substances
maximise energy efficiency
use renewable feedstock
avoid derivatives
use of catalyst
biodegradable product
real time analysis for pollution prevention
accident prevention
86
Q

ways to produce ethanoic acid

A 
fermentation
Wacker process (oxidation of ethene)
oxidation of naptha or butane
Monsanto process (carbonylation) (Rh)
Cativa process (carbonylation) (Ir cheaper)
87
Q

why a reaction proceed slowly

A

it has a high activation energy

chem (14 decks)

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