Industrial chem Flashcards
1
Q
How N2 become nitrate?
A
lightning–> N2 combines with oxygen –> NO2 –> dissolve in water to give nitrates
2
Q
effect of catalyst
A
increase rate of reaction by providing an alternative pathway with lower activation energy
3
Q
why NH3 is removed from catalytic chamber before eqm
A
- it takes a long time to reach eqm
2. to increase total amount of NH3 produced per unit time
4
Q
why methanol is important
A
act as a starting material to make organic compounds with larger carbon numbers.
5
Q
advancement of methanol production technology
A
conversion of biomass to syngas for methanol production –> renewable feed stocks
6
Q
why the initial rate is used
A
initial concentration is known
7
Q
maxwell boltzmann distribution curve axis
A
x = molecular kinetic energy y = fraction of molecules
8
Q
activation energy unit
A
kJ per mole
9
Q
how to produce Cl2 and NaOH
A
electrolysis of brine in flowing mercury cell
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
11
Q
definition of activation energy
A
minimum energy possessed by the colliding reactant particles in order that a reaction can occur
12
Q
why produce Vitamin C industrially
A
solve the problem of inadequate supply of vitamin C
13
Q
definition of initial rate
A
instantaneous rate at the start of a reaction
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
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
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
17
Q
why catalyst needs to be replaced
A
catalyst can be poisoned
18
Q
where to locate chloralkali industry
A
near the sea because easy to get raw materials
19
Q
mercury is…
A
poisonous
toxic not sure
20
Q
chlorine gas is….
A
poisonous
21
Q
why heat exchanger is used
A
- the hot gas from reaction chamber can help heat up hydrogen and nitrogen
- to save energy by conserving energy
22
Q
HCl is…
A
irritating
23
Q
enzyme is
A
- provide catalyst
2. biodegradable
24
Q
why reactants need to be purified if there is catalyst
A
impurities in the reaction mixture may poison the catalyst
25
raw material of manufacturing vitamin C
glucose
26
methanol to acetic acid
carbonylation
| CH3OH + CO -(HI)--> CH3COOH
27
how NaOH is obtained form membrane cell
1. use brine as electrolyte
2. membrane is permeable to cations but not anion
3. NaOH is obtained in the cathode compartment
28
high pressure -ve impact
high construction cost
29
what is window cleansing agent made of
dilute ammonia
30
why there is a distribution of kinetic energy of the oxygen molecules
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.
31
uses of methanol in everyday life
fuel and solvent
32
what is green chemistry
Green chemistry is a chemical technology that encourages the design of products and processes that reduce the use and generation of hazardous substances.
33
uses of ethanoic acid in industry
to make vinegar for food pickling
| to make esters which are used as artificial flavorings and solvents for paints and inks.
34
source of dioxin
combustion of PVC
35
why an increase in temperature can lead to an increase in the reaction rate
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
is a reaction with high atom economy means that it also has a high yield?
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
what is the use of the membrane in membrane cell
The membrane is permeable to cations but not anions
| NaOH solution is obtained in the cathode compartment
38
advantages of membrane cell overflowing mercury cell
no poisonous mercury
less energy required
less maintenance
39
why no solvent is greener
less solvent emit to the environment
40
advantage of using flowing mercury cell
high purity of hydrogen gas and chlorine gas produced
41
disadvantage of using flowing mercury cell
poisonous mercury may pollute the environment
42
why we cant simply use air as a source of N2
air contains O2
O2+ H2 --> explosion
and poison the catalyst
43
what is the purpose for using a drier in dealing with N2 and H2
to prevent water making Fe (the catalyst) to turn to Fe3O4 (poisoned)
any impurities present would poison the catalyst
44
what is the use of heat exchanger
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
why V2O5 instead of Pt is used in contact process
cheaper
| less likely to be poisoned than Pt
46
how to say the rate 八倍 in english
the rate increases by a factor of 8
47
in a reaction of A+B+C to D
| how to keep conc. of B and C constant
(B) (C) >>>>>(A)
so the rate only depends on concentration of A
48
what does second order mean
the rate is directly proportional to the square of concentration of the reactant
49
what is the change of color of end pt of reaction between MnO4 and H2O2
from colorless to pink
50
why should we add a small fixed amount of S2O32- to the reaction mixture
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
why should we add starch to signal the finishing point of the iodine clock reaction even though I2 has a color itself
if no starch
the color change will be colorless to pale yellow then yellow then brown
not obvious to be observed
52
explain collision theory
for a chemical reaction to occur, the reactants must have sufficient amount of energy and collide in the right direction
53
what is first order reaction
the rate of reaction is directly proportional to the concentration of the reactant
54
outline what measurements have to be taken in order to determine the activation energy of a reaction
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
what is activated complex
a highly unstable species at the maximum potential energy
| it cannot be detected or isolated
56
which step is the rate-determining step
the step with the largest activation energy
| slowest
57
if the rate determining step include intermediate
| should we include that in the rate equation?
NOOOO
| use the reactant that produces the intermediate to be included in the reaction
58
what does rate of reaction means
the rate of change in concentration of reactant or products
59
what does the overall order of a reaction means
the sum of powers to which the concentration are raised in the rate equation
60
why catatlyst need frequent replacement
they may be poisoned
they may react with impurities
the surface is covered with impurities
61
why the reaction rate of the equation 2I- + S2O82- is slow
due to the repulsion between the two negatively charged reactions
so it has a high activation energy
62
advantage of using catalyst in industrial process
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
what is fermentation
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
advantage of using enzymes in industrial process
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
what is the procedure of industrial process
raw materials to feedstocks to synthetic products
66
advantage of petrochemistry
large scale of production leads to cheaper product
| boost the economy of the society by increasing profit and job opportunities and infrastructure
67
disadvantage of petrochemistry
natural resources are limited and non-renewable
| pollution of all types has negative impacts on the environment
68
why shouldnt we obtain vitamin C from natural sources
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
what are the name of the two process of manufacturing Vitamin C
older: Reichstein
newer: two-step fermentation process (better)
70
why two-step fermentation process is better than Reichstein process
it uses less toxic solvents and reagents so it is more environmentally friendly
its overall cost is lower
71
why plants need N
to produce amino acid
72
what can be used to dry NH3
CaO
73
NH4NO3 is....
explosive
74
disadvantage of using fertilizers
growth of algae which float on water and cut off sunlight from the plants below
75
why farmers do not prefer using NH3 as a fertilizer
it has a pungent bad smell
it makes the soil too alkaline
it is difficult to transport
76
why ammonia solution is used in window cleaners
ammonia solution is alkaline and can assist the hydrolysis of oily dirt to form soluble compounds
77
why using ammonia solution instead of NaOH solution in window cleaner
sodium hydroxide is corrosive to skin
| ammonia is volatile
78
how atmospheric nitrogen can be converted to nitrates in soil
during lightning, nitrogen combines with oxygen to give nitrogen oxides
Nitrogen oxide dissolves in rainwater to give nitrates
79
how nitrogen in animal protein can return to soil
excretion of animals contain urea which is a soluble nitrogen compound
80
what are the potential hazard of bleach
it is irritating, toxic and corrosive
81
what is the special characteristics of membrane cell
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
importance of methanol
as a feedstock to make a wide variety of other chemicals
| as a solvent
83
what is green chemistry
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
what is sustainable development
it is the development which meets the needs of the present without compromising the ability of future generations to meet their own need
85
12 principle of green chemistry
```
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
ways to produce ethanoic acid
```
fermentation
Wacker process (oxidation of ethene)
oxidation of naptha or butane
Monsanto process (carbonylation) (Rh)
Cativa process (carbonylation) (Ir cheaper)
```
87
why a reaction proceed slowly
it has a high activation energy
