GATE Overflow for GATE ESE - Recent questions in Environmental Chemistry

GATE ES 2026 | Question: 12

Mon, 23 Feb 2026 13:15:26 +0000

The general atmospheric composition of gases in the decreasing order is $\_\_\_\_$.

$\mathrm{N}_{2}>\mathrm{O}_{2}>\mathrm{CO}>\mathrm{CO}_{2}>\mathrm{NH}_{3}$
$\mathrm{N}_{2}>\mathrm{O}_{2}>\mathrm{CO}_{2}>\mathrm{CO}>\mathrm{NH}_{3}$
$\mathrm{N}_{2}>\mathrm{CO}_{2}>\mathrm{O}_{2}>\mathrm{NH}_{3}>\mathrm{CO}$
$\mathrm{N}_{2}>\mathrm{CO}_{2}>\mathrm{NH}_{3}>\mathrm{CO}>\mathrm{O}_{2}$

GATE ES 2026 | Question: 18

Mon, 23 Feb 2026 13:15:14 +0000

Which of the following chemical reactions is/are related to smog formation in the troposphere?

$\mathrm{CFCl}_{3}+h v \rightarrow \mathrm{CFCl}_{2}+\mathrm{Cl} \cdot$
$\mathrm{CH}_{3} \mathrm{O}_{2}+\mathrm{NO}+\mathrm{O}_{2} \rightarrow \mathrm{HCHO}+\mathrm{HO}_{2}+\mathrm{NO}_{2}$
$\mathrm{NO}_{2}+\mathrm{O}_{2}+h v \xrightarrow{M} \mathrm{O}_{3}+\mathrm{NO}$
$\mathrm{CH}_{4}+8 \mathrm{O}_{2} \rightarrow \mathrm{CO}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{OH} \cdot+4 \mathrm{O}_{3}$

GATE ES 2026 | Question: 20

Mon, 23 Feb 2026 13:15:10 +0000

Which of the following options is/are CORRECTLY listing the species included in Total Kjeldahl Nitrogen (TKN) estimation of an aqueous sample?

Ammoniacal - $\text{N}$
Nitrite - $\text{N}$
Nitrate - $\text{N}$
Organic - $\text{N}$

GATE ES 2026 | Question: 31

Mon, 23 Feb 2026 13:14:49 +0000

The analysis of a water sample is shown in the table. The hardness of the water sample is $\_\_\_\_$ $\mathrm{mg} / \mathrm{L}$ as $\mathrm{CaCO}_{3}$.

Atomic weight $(\mathrm{g} / \mathrm{mol}): \mathrm{Ca}=40 ; \mathrm{Mg}=24 ; \mathrm{Na}=23 ; \mathrm{Cl}=35.5 ; \mathrm{S}=32 ; \mathrm{O}=16 ; \mathrm{N}=14$
$$\begin{array}{|c|c|}
\hline
\textbf{Species} & \textbf{Concentration } (\mathrm{mg/L}) \\
\hline
\mathrm{Na}^{+} & 30 \\
\hline
\mathrm{Ca}^{2+} & 10 \\
\hline
\mathrm{Mg}^{2+} & 15 \\
\hline
\mathrm{Cl}^{-} & 30 \\
\hline
\mathrm{SO}_{4}^{2-} & 60 \\
\hline
\mathrm{NO}_{3}^{-} & 5 \\
\hline
\end{array}$$

$87.5$
$62.5$
$25.5$
$47.5$

GATE ES 2026 | Question: 39

Mon, 23 Feb 2026 13:14:35 +0000

The mixing ratio of $\mathrm{CO}_{2}$ at a pressure of $1$ $\mathrm{atm}$ and at $300$ $\mathrm{K}$ is reported as $340$ $\mathrm{ppmv}$.

Considering ideal gas conditions, the equivalent concentration of $\mathrm{CO}_{2}$ in air is $\_\_\_\_\_\_$

$\mathrm{mg} / \mathrm{m}^{3}$ (rounded off to two decimal places).

The molecular weight of $\mathrm{CO}_{2}=44 \mathrm{~g} / \mathrm{mol}$

Universal gas constant $=8.314 \mathrm{~J} / \mathrm{mol}-\mathrm{K}$

GATE ES 2026 | Question: 41

Mon, 23 Feb 2026 13:14:33 +0000

The following two reactions describe the chemistry of $\text{S(IV)}$ in an aquatic system.

Under ideal conditions, the equilibrium constants for reactions $\text{(i)}$ and $\text{(ii)}$ are $1.3 \times 10^{-2} \mathrm{M}\left(\mathrm{K}_{\mathrm{S} 1}\right)$ and $6.6 \times 10^{-8} \mathrm{M}\left(\mathrm{K}_{\mathrm{S} 2}\right)$, respectively.

If the pH of the system is $4.0$ and the equilibrium concentration of $\mathrm{SO}_{2(\mathrm{aq})}$ is $1.0$ $\mathrm{M}$, the equilibrium concentration of $\mathrm{SO}_{3}^{2-}$ is $\_\_\_\_$ $\mathrm{mM}$ (rounded off to one decimal place).

$$\begin{array}{l}
\mathrm{SO}_{2(a q)} \rightleftharpoons \mathrm{H}^{+}+\mathrm{HSO}_{3}^{-} \quad \text{(i)}\\
\mathrm{HSO}_{3}^{-} \rightleftharpoons \mathrm{H}^{+}+\mathrm{SO}_{3}^{2-} \quad \text{(ii)}
\end{array}$$

GATE ES 2026 | Question: 42

Mon, 23 Feb 2026 13:14:32 +0000

The calibration graph between absorbance and the concentration of chromate $\left(\mathrm{CrO}_{4}{ }^{2-}\right)$ in a water sample is shown in the figure.

For an absorbance of $0.35$ in a water sample, the estimated $\mathrm{Cr}(\mathrm{VI})$ concentration is $\_\_\_\_$ $\mathrm{mg} / \mathrm{L}$ (rounded off to two decimal places).

Use the atomic weight $(\mathrm{g/mol})$ of $\text{Cr}$ and $\text{O}$ as $52$ and $16$, respectively.

GATE ES 2025 | Question: 4

Thu, 06 Mar 2025 16:22:50 +0000

Choose the redox reaction from the following

$\mathrm{H}_{2} \mathrm{CO}_{3} \leftrightarrow \mathrm{H}^{+}+\mathrm{HCO}_{3}^{-}$
$\mathrm{Hg}^{2+}+2 \mathrm{OH}^{-} \leftrightarrow \mathrm{Hg}(\mathrm{OH})_{2}$
$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2} \leftrightarrow 6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O}$
$\mathrm{CaCO}_{3}(\mathrm{~s}) \leftrightarrow \mathrm{Ca}^{2+}+\mathrm{CO}_{3}^{2-}$

GATE ES 2025 | Question: 16

Thu, 06 Mar 2025 16:22:16 +0000

Consider the following statements related to nitrification process:

Electron acceptor type vary depending on whether nitrosomonas or nitrobacter is involved.
Predominant carbon source is organic matter.
Predominant carbon source is inorganic carbon.
Electron donor during conversion of ammonium ions to nitrite ions is ammonium ions.

Choose the correct option(s) from the following

$(iii)$ and $(iv)$ are correct
$(i)$ and $(ii)$ are correct
$(i)$ is incorrect and $(iii)$ is correct
$(ii)$ is correct and $(iii)$ is incorrect

GATE ES 2025 | Question: 23

Thu, 06 Mar 2025 16:21:55 +0000

Choose the correct option(s) from the following regarding cumulative toxicity

Bioaccumulation is the process by which a living organism keeps on accumulating pollutants in its body due to continuous exposure, whereas, bio-magnification is the process by which higher order organisms accumulate more pollutants than the lower order organisms in a food chain.
Biomagnification is the process by which a living organism keeps on accumulating pollutants in its body due to continuous exposure, whereas, bioaccumulation is the process by which higher order organisms accumulate more pollutants than the lower order organisms in a food chain.
Bioaccumulation and biomagnification are possible with heavy metals, but not with pesticides and pharmaceutical compounds.
Bioaccumulation and biomagnification are possible with heavy metals, pesticides and pharmaceutical compounds

GATE ES 2025 | Question: 26

Thu, 06 Mar 2025 16:21:49 +0000

A researcher added certain amount of $\mathrm{HgCl}_{2}$ to water at $\mathrm{pH} 10$. He calculated the expected concentration of mercury in the water. He asked his student to measure the concentration. His student used an instrument that can measure only the free metal, $\mathrm{Hg}^{2+}$. The student observed that the concentration measured by him was significantly less than the concentration calculated by the researcher. How can he explain the paradox to the researcher?

Explanation $1$: Significant fraction of the mercury would have changed phase from aqueous to gaseous phase, thus leaving less mercury in the water.

Explanation $2$: Fraction of the mercury added to water would have formed aqueous complexes.

Explanation $3$: Fraction of the mercury added to water could have precipitated.

Choose the correct option from the following:

only Explanation $1$ is correct
Explanations $1$ and $2$ are correct
Explanations $1$ and $3$ are correct
Explanations $2$ and $3$ are correct

GATE ES 2025 | Question: 27

Thu, 06 Mar 2025 16:21:46 +0000

Correctly label the speciation diagram below:

$\mathrm{I}=\mathrm{PO}_{4}{ }^{3-}, \mathrm{II}=\mathrm{HPO}_{4}{ }^{2-}, \mathrm{III}=\mathrm{H}_{2} \mathrm{PO}_{4}{ }^{-}, \mathrm{IV}=\mathrm{H}_{3} \mathrm{PO}_{4}$
$\mathrm{I}=\mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{II}=\mathrm{HPO}_{4}{ }^{2-}, \mathrm{III}=\mathrm{H}_{2} \mathrm{PO}_{4}^{-}, \mathrm{IV}=\mathrm{PO}_{4}{ }^{3-}$
$\mathrm{I}=\mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{II}=\mathrm{H}_{2} \mathrm{PO}_{4}{ }^{-}, \mathrm{III}=\mathrm{HPO}_{4}{ }^{2-}, \mathrm{IV}=\mathrm{PO}_{4}{ }^{3-}$
$\mathrm{I}=\mathrm{PO}_{4}{ }^{3-}, \mathrm{II}=\mathrm{H}_{2} \mathrm{PO}_{4}^{-}, \mathrm{III}=\mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{IV}=\mathrm{HPO}_{4}{ }^{2-}$

GATE ES 2025 | Question: 33

Thu, 06 Mar 2025 16:21:27 +0000

Choose the correct option(s) from the following regarding the solubility in water

Water is a polar molecule because of the asymmetric distribution of charge between the oxygen and hydrogen atoms of the water molecule.
In a water molecule, the electrons shared between oxygen and hydrogen are attracted more towards the hydrogen atom.
Non-polar compounds are highly soluble in water because of their strong interaction with water molecules.
Aromaticity and charge of molecules influence their solubility in water.

GATE ES 2025 | Question: 49

Thu, 06 Mar 2025 16:21:00 +0000

A boiler burns coal at a rate of $1 \mathrm{~kg} / \mathrm{s}$. If the coal has $3 \%$ sulfur content, assuming that there is no sulfur in ash, $\mathrm{SO}_{2}$ emitted is $\_\_\_\_\_\_ \: \mathrm{kg} /$ day. (rounded off to nearest integer)

GATE ES 2025 | Question: 55

Thu, 06 Mar 2025 16:20:52 +0000

Water from a hand pump located near a landfill has $1 \mathrm{mg} / \mathrm{L}$ arsenic (oral carcinogenic potency factor $=1.75(\mathrm{~kg-day}) / \mathrm{mg})$. A person who lives nearby drinks $2 \mathrm{~L} /$ day water from this hand pump for $10$ years. Assume body weight of $70$ kg and $70$ years as average life duration. Chances of this person getting excess risk of cancer is $\_\_\_\_\_\_$ $\times 10^{-3}$. (rounded off to three decimal places)

GATE ES 2024 | Question: 2

Mon, 19 Feb 2024 10:24:14 +0000

Hardness in water is NOT caused by

$\mathrm{Ca}^{2+}$
$\mathrm{Si}^{2+}$
$\mathrm{Mg}^{2+}$
$\mathrm{CO}_{3}^{2-}$

GATE ES 2024 | Question: 6

Mon, 19 Feb 2024 10:24:13 +0000

Which one of the following conversions belongs to nonsymbiotic nitrogen fixation?

Atmospheric nitrogen to ammonia by Rhizobium bacteria in nodules attached to roots of legume
Atmospheric nitrogen to ammonia by Azotobacter
Nitrate to gaseous nitrogen under anaerobic condition
Nitrate to ammonia under aerobic conditions

GATE ES 2024 | Question: 7

Mon, 19 Feb 2024 10:24:13 +0000

Crown corrosion of reinforced cement concrete sewer is caused by ___________.

sulfur oxidizing bacteria
iron oxidizing bacteria
denitrifying bacteria
fermentative bacteria

GATE ES 2024 | Question: 9

Mon, 19 Feb 2024 10:24:12 +0000

The environmental temperature increases by $6^{\circ} \mathrm{C} / \mathrm{km}$ with height at a particular location. The stability condition of the atmosphere at the location is

stable
unstable
inversion
neutral

GATE ES 2024 | Question: 28

Mon, 19 Feb 2024 10:24:09 +0000

A saturated $\mathrm{CaCO}_{3}$ stock solution is existing at $25^{\circ} \mathrm{C}$. In one experiment $\text{(i)}$ $25 \mathrm{~g}$ $\mathrm{Na}_{2} \mathrm{CO}_{3}$ is added to the stock solution. In another experiment $\text{(ii)}$ $25 \mathrm{~g} \mathrm{Na}_{2} \mathrm{SO}_{4}$ is added to the stock solution. Select the correct statement from the following.

Addition of $\text{(i)}$ increases the concentration of $\mathrm{Ca}^{2+}$ and addition of $\text{(ii)}$ decreases the concentration of $\mathrm{Ca}^{2+}$
Addition of $\text{(i)}$ decreases the concentration of $\mathrm{Ca}^{2+}$ and addition of $\text{(ii)}$ increases the concentration of $\mathrm{Ca}^{2+}$
Addition of $\text{(i)}$ and $\text{(ii)}$ increase the concentration of $\mathrm{Ca}^{2+}$
Addition of $\text{(i)}$ and $\text{(ii)}$ decrease the concentration of $\mathrm{Ca}^{2+}$

GATE ES 2024 | Question: 40

Mon, 19 Feb 2024 10:24:07 +0000

The $\mathrm{pH}$ of a solution containing $0.1 \mathrm{M}$ of acetic acid and $0.05 \mathrm{M}$ of sodium acetate is __________ $\text{(rounded off to $2$ decimal places)}$.

The $\mathrm{pK}_{\mathrm{a}}$ value of ionization of acetic acid is $4.76$.

GATE ES 2024 | Question: 41

Mon, 19 Feb 2024 10:24:07 +0000

The ionic strength of a solution containing $0.01 \mathrm{M}$ of $\mathrm{CaCl}_{2}$ and $0.001 \mathrm{M}$ of $\mathrm{Na}_{2} \mathrm{SO}_{4}$ is _________ $\mathrm{M}$ $\text{(rounded off to $3$ decimal places)}$.

GATE ES 2024 | Question: 42

Mon, 19 Feb 2024 10:24:06 +0000

The concentration of Ozone corresponding to a mixing ratio of $120 \mathrm{ppbv}$ at pressure of $1$ atmosphere and temperature of $25^{\circ} \mathrm{C}$ is ________ $\mu \mathrm{g} / \mathrm{m}^{3}$ $\text{(rounded off to $1$ decimal place)}$.

Atomic weight of oxygen $=16 ; \mathrm{R}=8.314 \mathrm{~J} / \mathrm{K}-\mathrm{g}$. mole.

GATE ES 2024 | Question: 44

Mon, 19 Feb 2024 10:24:06 +0000

An industry discharges $2$ million liters per day $\text{(MLD)}$ of wastewater with a temperature of $45^{\circ} \mathrm{C}$ and a $\mathrm{pH}$ of $2$, whereas the neighboring industry produces $3 \mathrm{MLD}$ of wastewater with a temperature of $30^{\circ} \mathrm{C}$ and $\mathrm{pH}$ of $8$. If both the wastewaters are mixed and carried through a pipeline, then the resultant $\mathrm{pH}$ of mixed wastewater is _________ $\text{(rounded off to $2$ decimal places)}$.

Neglect buffering capacity of the system and the temperature effect on $\mathrm{pH}$.

GATE ES 2024 | Question: 53

Mon, 19 Feb 2024 10:24:05 +0000

A person consumes $2.5$ liters of water per day. The water quality test indicated that the supplied water has a $\mathrm{Pb}$ concentration of $0.6 \mathrm{mg} / \mathrm{L}$. If the weight of the person is $75 \mathrm{~kg}$, the exposure level for $\mathrm{Pb}$ for this person from this drinking water source is __________ $\mathrm{mg} / \mathrm{kg} /$ day $\text{(rounded off to $2$ decimal places)}$.

GATE ES 2024 | Question: 50

Mon, 19 Feb 2024 10:24:05 +0000

Two hypothetical organic waste streams A and B are mixed prior to the composting process. Waste-A has $2.16 \%$ of $\mathrm{C}$ and $1.20 \%$ of N. Waste-B has $19.10 \%$ of $\mathrm{C}$ and $0.14 \%$ of N. The quantity of Waste-B that should be mixed with per kg of Waste-A to achieve the desired C:N ratio of 25 is __________ $\mathrm{kg}$ $\text{(rounded off to $2$ decimal places)}$.

Assume both the waste streams are completely dry.

GATE ES 2024 | Question: 55

Mon, 19 Feb 2024 10:24:04 +0000

Initially a bottle contained $400 \mathrm{~g}$ of ethanol. Half of ethanol was used by a student for preparing the stock solution in an environmental chemistry laboratory just before summer vacation of $90$ days. After completing the procedure, the student left the bottle uncorked. If the unsealed bottle losses ethanol at a rate of $0.5 \mathrm{~g} /$ day, the ethanol that will be left in the bottle at the end of the summer vacation is ___________ $\mathrm{g}$ $\text{(an integer value)}$.

GATE ES 2023 | Question: 4

Tue, 23 May 2023 03:12:47 +0000

For testing alkalinity for a water sample, first phenolphthalein indicator is added. The water remains colorless. However, when a few drops of methyl orange is added to the sample, the color turns yellow. As per these observations, the correct choice is

Absence of $\mathrm{CO}_{3}{ }^{2-}$ and/or $\mathrm{HCO}_{3}{ }^{-}$but the presence of $\mathrm{OH}^{-}$ions in the sample
Presence of $\mathrm{CO}_{3}{ }^{2-}$ and/or $\mathrm{HCO}_{3}{ }^{-}$but the absence of $\mathrm{OH}^{-}$ions in the sample
Absence of $\mathrm{CO}_{3}{ }^{2-}, \mathrm{HCO}_{3}{ }^{-}$and $\mathrm{OH}^{-}$ions in the sample
Presence of $\mathrm{CO}_{3}{ }^{2-}, \mathrm{HCO}_{3}{ }^{-}$and $\mathrm{OH}^{-}$ions in the sample

GATE ES 2023 | Question: 31

Tue, 23 May 2023 03:12:09 +0000

Match the following

J) Dalton's law	i) Diffusion
K) Fick's law	ii) Pressure exerted by a mixture of gases
L) Henry's law	iii) Gravitational settling
M) Stoke's law	iv) Gas-liquid phase transfe

$\mathrm{J}-\mathrm{ii} ; \mathrm{K}-\mathrm{i} ; \mathrm{L}-\mathrm{iv} ; \mathrm{M}-\mathrm{iii}$
$\mathrm{J}-\mathrm{iii} ; \mathrm{K}-\mathrm{ii} ; \mathrm{L}-\mathrm{i} ; \mathrm{M}-\mathrm{iv}$
$\mathrm{J}-\mathrm{ii} ; \mathrm{K}-\mathrm{iii} ; \mathrm{L}-\mathrm{iv} ; \mathrm{M}-\mathrm{i}$
$\mathrm{J}-\mathrm{i} ; \mathrm{K}-\mathrm{iv} ; \mathrm{L}-\mathrm{ii} ; \mathrm{M}-\mathrm{iii}$

GATE ES 2023 | Question: 32

Tue, 23 May 2023 03:12:08 +0000

Read the following statements

I. According to the Liebig's law of minimum, the growth is regulated by the limited factors i.e., resources in scarcity and not by the resources in abundance.

II. Shelford's law of tolerance states that, only the factors present in excess/abundance can affect the growth, development of an organism or rate of biological process.

III. Shelford's law of tolerance states that, an organism's success is based on a complex set of conditions and that each organism has a certain minimum, maximum, and optimum levels of environmental factor or combination of factors that determine success.

The correct choice is

$\text{I}$ and $\text{II}$ are correct; $\text{III}$ is incorrect
$\text{I}$ and $\text{III}$ are correct; $\text{II}$ is incorrect
$\text{II}$ is correct; $\text{I}$ and $\text{III}$ are incorrect
$\text{III}$ is correct; $\text{I}$ and $\text{II}$ are incorrect

GATE ES 2023 | Question: 33

Tue, 23 May 2023 03:12:07 +0000

Read the following statements

Trivalent chromium has relatively low aqueous solubility, and low mobility in the soil environment. By contrast, hexavalent chromium has a higher aqueous solubility and greater mobility in the soil environment.
The chemical reaction between trivalent chromium and zero-valent iron will result in transformed version called hexavalent chromium.
Hexavalent chromium is a known carcinogen.
Trivalent chromium has relatively higher human toxicity as compared to hexavalent chromium.

The correct choice is

IV is correct; I and III are incorrect
II is correct; I and IV are incorrect
I and III are correct; II and IV are incorrect
I, II and IV are correct; III is incorrect

GATE ES 2023 | Question: 40

Tue, 23 May 2023 03:11:59 +0000

The solubility of gas A is $16 \mathrm{mg} / \mathrm{L}$ in water and its vapor pressure is $0.042 \mathrm{~atm}$. at $25^{\circ} \mathrm{C}$. In a closed system, the gas phase concentration of $\mathrm{A}$ is $10^{-3} \mathrm{~mol} / \mathrm{L}$. Assuming Ideal gas constant $(\mathrm{R})$ value as $0.0821 \mathrm{~L}-\mathrm{atm} / \mathrm{mol}-\mathrm{K}$, the concentration of gas $\mathrm{A}$ in water at $25^{\circ} \mathrm{C}$ is ___________ (in $\mathrm{mg} / \mathrm{L}$, $\text{rounded off to two decimal places).}$

GATE ES 2023 | Question: 49

Tue, 23 May 2023 03:11:49 +0000

In a $30 \mathrm{~m}^{3}$ room, a stove in operation consumes wood at the rate of $0.25 \mathrm{~kg} / \mathrm{h}$. The inflow and outflow rate of air in the room is the same, i.e. $500 \mathrm{~m}^{3} / \mathrm{h}$. This stove emits a VOC species at a rate of $0.2 \mathrm{~g} / \mathrm{kg}$-wood. The VOC species gets converted to $\mathrm{CO}_{2}$ at a rate of 0.4 per hour. Given: (i) the air in the room is completely mixed, (ii) initial concentration of the VOC species in the room is negligible, and (iii) concentration of the VOC species in the air entering the room is negligible. The concentration of the VOC species due to two hours of stove operation in the room is ___________ (in $\mu \mathrm{g} / \mathrm{m}^{3}$, $\text{rounded off to one decimal place).}$

GATE ES 2021 | Question: 3

Tue, 14 Mar 2023 03:44:48 +0000

The table below shows the carbon content of four samples of powdered coal. If these four samples are mixed completely, what would be the resultant carbon percentage of the mixture by weight?
\begin{array}{|c|c|c|}
\hline Sample number & Mass of sample (kg) & Carbon \% by weight \\
\hline 1 & 2 & 88 \\
\hline 2 & 1 & 90 \\
\hline 3 & 2 & 80 \\
\hline 4 & 1 & 90 \\
\hline
\end{array}

$58 \%$
$86 \%$
$87 \%$
$90 \%$

GATE ES 2021 | Question: 15

Tue, 14 Mar 2023 03:44:32 +0000

Chlorine is most effective as a water disinfectant at a $\text{pH}$ of _____________.

$6$
$8$
$10$
$12$

GATE ES 2021 | Question: 16

Tue, 14 Mar 2023 03:44:31 +0000

The oxidation states of ' $\mathrm{N}$ ' in $\mathrm{NH}_{4}^{+}, \mathrm{NO}_{2}^{-}$, and $\mathrm{NO}$ are ________ respectively.

$+2,-3$, and +3
$-3,+3$, and +2
$-3,+3$, and -4
$+4,-2$, and +2

GATE ES 2021 | Question: 17

Tue, 14 Mar 2023 03:44:30 +0000

What is the $\text{pH}$ of a water sample having $\mathrm{H}^{+}$ concentration of $10$ $\mathrm{mg} / \mathrm{L}$?
The atomic weight of $\mathrm{H}$ is $1 \mathrm{~g} / \mathrm{mol}$.

GATE ES 2021 | Question: 19

Tue, 14 Mar 2023 03:44:29 +0000

Which of the following is/are both greenhouse gas(es) and ozone depleting substance(s)?

$\text{CFC-11}$
$\mathrm{CO}_{2}$
$\text{HCFC-22}$
$\mathrm{N}_{2} \mathrm{O}$

GATE ES 2021 | Question: 22

Tue, 14 Mar 2023 03:44:27 +0000

A wind rose is a representation of meteorological conditions. Which of the following is/are included in this representation?

Mixing height
Wind speed
Wind direction
Percentage of time

GATE ES 2021 | Question: 31

Tue, 14 Mar 2023 03:44:18 +0000

A $200 \mathrm{~mL}$ sample of water has an initial $\mathrm{pH}=9$. In order to determine alkalinity, the sample was titrated using $0.02 \mathrm{~N} \mathrm{H}_2 \mathrm{SO}_4$ acid to an end point of $\mathrm{pH}=4.5$. In the titration, $25 \mathrm{~mL}$ of $0.02 \mathrm{~N}$ $\mathrm{H}_2 \mathrm{SO}_4$ acid was required. What is the total alkalinity of the sample in ' $\mathrm{mg} / \mathrm{L}$ as $\mathrm{NaHCO}_3$ '?
[Atomic weight (g/mol): $\mathrm{Ca}=40, \mathrm{Na}=23, \mathrm{H}=1, \mathrm{C}=12, \mathrm{~S}=32$, and $\mathrm{O}=16]$

$2$
$12$
$21$
$305$

GATE ES 2021 | Question: 34

Tue, 14 Mar 2023 03:44:08 +0000

The characteristics of a water sample are as follows: $\mathrm{Na}^{+}=92 \mathrm{mg} / \mathrm{L}$, $\mathrm{K}^{+}=19.5 \mathrm{mg} / \mathrm{L}, \mathrm{Ca}^{2+}=40 \mathrm{mg} / \mathrm{L}$, and $\mathrm{Mg}^{2+}=24 \mathrm{mg} / \mathrm{L}$. What is the sodium adsorption ratio (SAR) of the water sample which may be considered for irrigation purposes?
[Atomic weight $(\mathrm{g} / \mathrm{mol}): \mathrm{Na}=23, \mathrm{~K}=39, \mathrm{Ca}=40$, and $\mathrm{Mg}=24$ ]

$2.8$
$1.9$
$2.0$
$4.00$

GATE ES 2021 | Question: 39

Tue, 14 Mar 2023 03:44:00 +0000

In the context of water quality, which of the following is/are correct for the most probable number $\text{(MPN)}$ of a water sample?

The estimated organisms are gram negative.
It is based on the assumption of Poisson distribution.
It measures the exact number of microorganisms present in the sample.
It includes the quantification of pathogenic virus.

GATE ES 2021 | Question: 53

Tue, 14 Mar 2023 03:43:49 +0000

The molar concentrations $(M$, i.e. $m o l / L)$ of some ionic species in a water sample were estimated as follows:
$\mathrm{Na}^{+}=0.25{\mathrm{M} ; \mathrm{Ca}^{2+}}^{2}=0.12 \mathrm{M} ; \mathrm{Cl}^{-}=0.32 \mathrm{M} ; \mathrm{HCO}_{3}^{-}=0.05 \mathrm{M}$.
The ionic strength of this water sample is __________$\mathrm{M}$ $\text{(correct up to two decimal places)}$.

GATE ES 2021 | Question: 54

Tue, 14 Mar 2023 03:43:49 +0000

Excess amount of solid calcium sulphate $\left(\mathrm{CaSO}_4\right)$ was added to a pure water sample $(\mathrm{pH}=7)$ so that some solids remain undissolved at the equilibrium. The solubility product of $\mathrm{CaSO}_4$ is $2 \times 10^{-5}$ $\mathrm{mol}^2 / \mathrm{L}^2$. The molar concentration of $\mathrm{SO}_4^{2-}$ in this water sample at equilibrium will be ____________ $\mathrm{mol} / \mathrm{L}$ $\text{(rounded off to three decimal places)}$.

GATE ES 2022 | Question: 5

Fri, 17 Feb 2023 07:06:13 +0000

Specific conductance is used in water analysis to indirectly estimate dissolved solids. The measurements used in the method accounts for

Cations only
All ions
Anions only
Un-ionized species

GATE ES 2022 | Question: 11

Fri, 17 Feb 2023 07:06:09 +0000

Carbon dioxide is used in recarbonation process. A solution has $1 \mathrm{~mole} / \mathrm{L}$ supersaturated calcium carbonate. Estimated amount of carbon dioxide (in grams) needed to completely convert calcium carbonate to calcium ions in $1$ litre solution is

$44.000$ gram
$0.044$ gram
$40.000$ gram
$0.040$ gram

GATE ES 2022 | Question: 18

Fri, 17 Feb 2023 07:05:58 +0000

If G represents Gibbs free energy, select the correct statement(s)

If $\Delta \mathrm{G}=0$, reaction will proceed only in one direction
If $\Delta \mathrm{G}=0$, reaction will be in equilibrium
If $\Delta \mathrm{G}<0$, reaction will proceed forward
If $\Delta \mathrm{G}>0$, reaction will not proceed forward

GATE ES 2022 | Question: 19

Fri, 17 Feb 2023 07:05:57 +0000

For effluents generated by a molasses based distillery and wood based pulp and paper industry, which of the following statement(s) is/are NOT correct?

Both the effluents have dark colour.
Both the effluents have high toxicity.
Both the effluents generally have BOD greater than $15,000$ ppm.
Both the effluents have high $\mathrm{pH}$.

GATE ES 2022 | Question: 33

Fri, 17 Feb 2023 07:05:48 +0000

During night, in troposphere, which of the following is/are NOT correct

$\quad \mathrm{NO}_{2}+\mathrm{ho} \rightarrow \mathrm{NO}+\mathrm{O}$
Most of the $\mathrm{NOx}$ (i.e., $\mathrm{NO}+\mathrm{NO}_{2}$ ) converts to $\mathrm{NO}$
$\mathrm{NO}+\mathrm{O}_{3} \rightarrow \mathrm{NO}_{2}+\mathrm{O}_{2}$
Most of the $\mathrm{NOx}$ (i.e., $\mathrm{NO}+\mathrm{NO}_{2}$ ) converts to $\mathrm{NO}_{2}$

GATE ES 2022 | Question: 40

Fri, 17 Feb 2023 07:05:43 +0000

Carbon cycle, nitrogen cycle and phosphorus cycle play important role in the ecosystems. Which of the following statement(s) is/are NOT correct about the phosphorus cycle?

Shortage of phosphorus can be a limiting factor in many ecosystems, however, its excess can stimulate eutrophication.
Organic phosphates exist in various rock and soil minerals.
Like carbon cycle, phosphorus also has a gaseous phase and can move into far away ecosystems.
Human interventions like application of phosphorus fertilizers cause much phosphorus to get into the ocean.