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Environmental Chemistry [ Question No: 1 To 20 ] :
Peroxyacetyl Nitrate (PAN) is formed by oxidation of
(i) Hydrocarbons
(ii) Isoprene
(iii) Terpene
(iv) Arsenic
Choose the correct answer from the codes :
Codes :
Hardness of water is due to the presence of
The soil type which is good for agriculture is
Particles which have maximum ability to attract and hold K\(^{+}\), Ca\(^{++}\) and NH\(_{4}^{+}\) ions on their surface are
In turbidity analysis, formazin is used
Halon - 1301 is a
Two water samples were collected.
Sample # 1 : pH = 9, but no carbonate or other dissolved proton donors or acceptors.
Sample # 2 : pH = 8.3, but it contains dissolved \(\mathrm{NaHCO_{3}}\) at a concentration of 0.01/mg/l
Which of the following is true based on the above observations.
Quantity of 5M HCl required for preparing 1000 ml of 0.1 M HCl is,
During the determination of COD, sulphanilic acid is added, because
The metal which is generally absorbed by plants along with Zn and causes "Ouch Ouch" disease in human beings is
The wavelength range of UV-C radiation is
Which of the following analytical techniques is not used for organic determination directly ?
Which one of the following is incorrect about POPs ?
Arrange the following gases in decreasing order of their concentration in atmosphere :
How many moles of iron are there in 122 of Fe ? (MW of iron is 55.858)
According to Beer's law, the intensity of transmitted light is decreased in proportion of :
The loam soil is composed of :
Generally the rain water having pH ......................... is considered as acid rain.
Law stating that the gas dissolved in a liquid is proportional to its partial pressure is called as :
Stratosphere is known to protect life on earth from harmful radiation from sun is found between :
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20
Environmental Chemistry [ Question No: 1 To 20 ] :
Peroxyacetyl Nitrate (PAN) is formed by oxidation of
(i) Hydrocarbons
(ii) Isoprene
(iii) Terpene
(iv) Arsenic
Choose the correct answer from the codes :
Codes :
Your Answer : (Not Answered)
Correct Answer : D
(i), (ii) and (iii)
Peroxyacetyl nitrate is a secondary pollutant of photochemical smog formed from hydrocarbons, including isoprene and terpenes, which are reactive hydrocarbons given off by plants. Arsenic is a metalloid and has no part in PAN formation, so every option containing statement (iv) is wrong.
The other options, (i) and (iv); (ii) and (iv); (iii) and (iv), are not the answer to this question. This agrees with the official final answer key for the paper, which gives option D.
Hardness of water is due to the presence of
Your Answer : (Not Answered)
Correct Answer : A
Hardness of water is due to the presence of calcium and magnesium ions, option (A). These ions, present as bicarbonates, sulphates and chlorides, form scum with soap and scale in boilers.
Strontium, sodium, potassium, nitrate, chloride and nitrite ions do not make water hard in the usual sense. Sodium and potassium salts do not form insoluble soaps, so they do not cause hardness.
Temporary hardness is due to bicarbonates of calcium and magnesium and can be removed by boiling, while permanent hardness is due to their sulphates and chlorides.
The soil type which is good for agriculture is
Your Answer : (Not Answered)
Correct Answer : B
Latosols
Latosols, the deep tropical soils, are the soil type in the key as good for agriculture when managed. Podzols are acidic and leached, serpentine soils are poor in nutrients and carry toxic metals, and solonchak is saline, so these three are unfit for ordinary crops.
The other options, Podozols; Serpent soil; Solonachak, are not the answer to this question. This agrees with the official final answer key for the paper, which gives option B.
Particles which have maximum ability to attract and hold K\(^{+}\), Ca\(^{++}\) and NH\(_{4}^{+}\) ions on their surface are
Your Answer : (Not Answered)
Correct Answer : A
The particles with the greatest ability to attract and hold the cations K+, Ca++ and NH4+ are clay, option (A). Clay particles are very small, so they have a large surface area, and they carry a negative charge, which gives them a high cation exchange capacity. Sand (B) has little surface and almost no charge, so it holds few ions. Loam (C) and loamy sand (D) are mixtures, with less clay than a clay soil, so their holding power is lower.
In turbidity analysis, formazin is used
Your Answer : (Not Answered)
Correct Answer : C
In turbidity analysis formazin is used to make turbidity standards, option (C). A formazin polymer suspension prepared from hydrazine sulphate and hexamethylenetetramine is reproducible, and its turbidity is defined in nephelometric turbidity units, so samples are compared against it. It is not used to stabilise (A) or to preserve (B) the samples, nor to remove colour interferences (D), which is done by filtering or by other correction methods.
Halon - 1301 is a
Your Answer : (Not Answered)
Correct Answer : A
Halon 1301 is a fire extinguishing agent.
Halon 1301 is bromotrifluoromethane, CBrF3. It is a gaseous agent that is used for total flooding systems in computer rooms, aircraft and control rooms, because it puts out fires by interrupting the combustion chain reaction and leaves no residue on equipment. Its bromine destroys stratospheric ozone, which is why its production was phased out under the Montreal Protocol.
It is not used as a solvent (CFC-113 and methyl chloroform were), as a refrigerant (CFC-12 was) or as an aerosol propellant (CFC-11 and CFC-12 were), though these chemicals are related to it.
Two water samples were collected.
Sample # 1 : pH = 9, but no carbonate or other dissolved proton donors or acceptors.
Sample # 2 : pH = 8.3, but it contains dissolved \(\mathrm{NaHCO_{3}}\) at a concentration of 0.01/mg/l
Which of the following is true based on the above observations.
Your Answer : (Not Answered)
Correct Answer : B
Sample 2 has more alkalinity, according to the key.
Alkalinity is the capacity to accept protons. Sample 1 has no carbonate or other proton acceptors, so its alkalinity comes only from hydroxide at pH 9, about \(10^{-5}\) equivalents per litre, which is very small. Sample 2 contains dissolved sodium bicarbonate, and the bicarbonate ion accepts protons, so its alkalinity is that of the bicarbonate present plus the small hydroxide term.
The concentration of sample 2 is printed as 0.01/mg/l, and the key reads it as a concentration large enough to give sample 2 the larger alkalinity (as would 0.01 mol per litre). The samples differ, so 'exactly the same' is wrong, and alkalinity can be estimated for both, so 'cannot be estimated' is wrong too.
Quantity of 5M HCl required for preparing 1000 ml of 0.1 M HCl is,
Your Answer : (Not Answered)
Correct Answer : A
The volume of 5 M HCl needed is 20 ml. Use the dilution relation: the amount of HCl in the diluted solution equals the amount taken from the stock.
\[ M_1 V_1 = M_2 V_2 \]
\[ 5 \times V_1 = 0.1 \times 1000 \]
\[ V_1 = 20 \text{ ml} \]
So 20 ml of stock acid is made up to 1000 ml with water. The figures 2 ml, 200 ml and 100 ml come from slips of a factor of ten or from misreading the molarities; for 2 ml the stock would have to be 50 M, and for 200 ml the product would give 1 M. The answer is option A.
During the determination of COD, sulphanilic acid is added, because
Your Answer : (Not Answered)
Correct Answer : C
The keyed answer is that the added acid removes the nitrite interference in the COD test, which is the closest of the four statements.
Nitrite is oxidised by dichromate and would add to the measured oxygen demand, so a small amount of a sulphonic acid reagent (sulfamic acid in the standard method) is added to destroy it. The keyed wording says the nitrite is oxidised to nitrate, which is the intended point: the nitrite no longer consumes dichromate. Silver sulphate, not this acid, acts as the catalyst, and mercuric sulphate, not this acid, binds the chloride, so the other statements do not apply. The acid does not keep the mixture acidic (sulphuric acid does that) and does not react with ferrous ammonium sulphate, the titrant.
The metal which is generally absorbed by plants along with Zn and causes "Ouch Ouch" disease in human beings is
Your Answer : (Not Answered)
Correct Answer : B
Cadmium, taken up by plants along with zinc, is the metal that causes Itai-Itai (ouch-ouch) disease, which came from contaminated rice in Japan and which causes bone pain and kidney damage. Lead, mercury and chromium cause other diseases: mercury causes Minamata disease. The answer is Cd.
The wavelength range of UV-C radiation is
Your Answer : (Not Answered)
Correct Answer : D
The keyed answer is 240 to 280 nm, option D. UV-C is the short wavelength band of ultraviolet radiation, which extends from 100 to 280 nm, and the range of option D lies in this band, where the radiation is strongly germicidal.
The range 320 to 400 nm (option A) is UV-A, and the range 280 to 320 nm (option B) is UV-B. The range 100 to 1500 nm (option C) is far too wide and takes in visible and infrared light. The key picks the range that is wholly within UV-C.
Which of the following analytical techniques is not used for organic determination directly ?
Your Answer : (Not Answered)
Correct Answer : C
The technique not used directly for organic determination is AAS, atomic absorption spectroscopy.
AAS measures the absorption of light by free atoms in a flame or furnace, and is used for metals and some metalloids, such as lead, cadmium, mercury and zinc. Organic compounds are destroyed in the atomiser, so AAS cannot identify or measure them directly.
The other three are separation methods for organic compounds. Gas chromatography (GC) separates volatile organics such as pesticides and solvents. High-performance liquid chromatography (HPLC) handles non-volatile and heat-sensitive organics. Thin-layer chromatography (TLC) is a simple method for separating and identifying organic mixtures.
Which one of the following is incorrect about POPs ?
Your Answer : (Not Answered)
Correct Answer : C
The incorrect pairing is Aldrin - to control fungi.
Aldrin is an organochlorine insecticide. It was used against soil insects such as termites and rootworms, not as a fungicide, and it is one of the original twelve POPs under the Stockholm Convention.
The other pairings are correct: endosulfan was used against crop pests, DDT against mosquitoes and other disease vectors, and chlordane against termites.
Arrange the following gases in decreasing order of their concentration in atmosphere :
Your Answer : (Not Answered)
Correct Answer : B
The decreasing order is CO2, CH4, O3.
Carbon dioxide is now above 400 ppm in the atmosphere. Methane is about 1.9 ppm. Ozone, averaged through the whole atmosphere, is far less, of the order of a few hundredths of a ppm near the ground and at most about 10 ppm in the stratospheric peak.
So the gas in the hundreds of ppm comes first and ozone last. The orders starting with CH4 or O3 put a trace gas ahead of carbon dioxide, which is roughly two hundred times more abundant than methane.
How many moles of iron are there in 122 of Fe ? (MW of iron is 55.858)
Your Answer : (Not Answered)
Correct Answer : C
122 g of iron is 2.18 mol Fe.
The number of moles is mass divided by molar mass (the paper prints '122 of Fe', meaning 122 g):
\[ n = \frac{122}{55.858} \approx 2.18\ \text{mol} \]
As a check, 2 mol of iron is about 111.7 g and 2.2 mol about 122.9 g, so 122 g lies just below 2.2 mol.
1.28 and 1.18 mol would weigh only about 66 to 72 g, and 8.12 mol would be about 454 g.
According to Beer's law, the intensity of transmitted light is decreased in proportion of :
Your Answer : (Not Answered)
Correct Answer : B
By Beer's law, transmitted intensity falls in proportion to Concentration.
The combined Beer-Lambert law says absorbance is proportional to both the path length and the concentration of the absorbing species:
\[ A = \log \frac{I_{0}}{I} = \varepsilon\, l\, c \]
Historically, Lambert's law deals with the path length (distance through the sample) and Beer's law with the concentration. That is the basis of colorimetric and spectrophotometric analysis of pollutants: absorbance is read and converted to concentration from a calibration curve.
Distance is Lambert's variable, so it is the trap here. Volume and time do not enter either law.
The loam soil is composed of :
Your Answer : (Not Answered)
Correct Answer : C
The keyed composition is sand + gravel + silt + clay.
Loam is a soil texture class containing a balanced mixture of the three fine-earth fractions, sand, silt and clay, roughly 40 per cent sand, 40 per cent silt and 20 per cent clay. Gravel is coarser than the fine earth and is not part of the texture definition, but this is the only option that contains all three of sand, silt and clay.
Clay and sand alone, sand and silt alone, or sand, gravel and clay each leave out one of the fractions that make a loam.
Generally the rain water having pH ......................... is considered as acid rain.
Your Answer : (Not Answered)
Correct Answer : B
Acid rain is rain with a pH less than 5.6.
Even unpolluted rain is slightly acidic: carbon dioxide dissolves in it to form carbonic acid, and water in equilibrium with atmospheric carbon dioxide has a pH of about 5.6. Rain is called acid rain only when it is more acidic than that, which happens when sulphur dioxide and nitrogen oxides form sulphuric and nitric acids.
A pH above 5.6 is less acidic than natural rain. A pH of 7 is neutral, and a pH of 10 is alkaline, so neither describes acid rain.
Law stating that the gas dissolved in a liquid is proportional to its partial pressure is called as :
Your Answer : (Not Answered)
Correct Answer : C
It is Henry's law.
Henry's law states that at constant temperature the amount of a gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid:
\[ C = k_{H}\, p \]
It explains why opening a soda releases dissolved CO2 and governs oxygen transfer in aeration tanks. Lambert's law and Beer's law relate the absorption of light to path length and concentration, the basis of spectrophotometry. Rutherford's name belongs to atomic structure and scattering, not to gas solubility.
Stratosphere is known to protect life on earth from harmful radiation from sun is found between :
Your Answer : (Not Answered)
Correct Answer : C
The stratosphere lies between the troposphere and the mesosphere (printed 'Toposphere & Mesosphere').
The layers of the atmosphere, from the ground up, are the troposphere (to about 8-18 km), the stratosphere (to about 50 km), the mesosphere (to about 85 km) and the thermosphere. The stratosphere contains the ozone layer, which absorbs most of the sun's harmful ultraviolet radiation, which is why it is said to protect life.
The mesosphere and thermosphere lie above the stratosphere, and the ionosphere and exosphere are higher still, overlapping the thermosphere and the outer edge of the atmosphere. None of these pairs encloses the stratosphere.
Marks
Total number of questions : 20
Number of answered questions : 0
Number of unanswered questions : 20