1 Marks Question

Question 11 Mark

Why is CO more toxic than $\mathrm{CO}_2$?

Answer

Carbon monoxide reacts with haemoglobin to form carboxy -haemoglobin which does not act as oxygen carrier, therefore, it is more harmful than $\mathrm{CO}_2$.

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Question 21 Mark

What are viable and non-viable particulates?

Answer

Viable particulates are small size living organisms such as bacteria, fungi, moulds, algae, etc. Non-viable particulates are formed by disintegration of large size materials or condensation of small size particles or droplets, e.g. mist, smoke, fume and dust.

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Question 31 Mark

Acid rain is known to contain some acids. Name these acids and where from they come in rain?

Answer

The acids commonly present in acid rain are nitric acid, sulphuric acid and carbonic acid. Nitric acid is formed by oxidation of nitric oxide present in air to $\mathrm{NO}_2$ & $\mathrm{NO}_3$, which dissolve in water also present in air. Sulphuric acid is formed by the oxidation of $\mathrm{SO}_2$ result in air to $\mathrm{SO}_3$ followed by dissolution in water. $\mathrm{CO}_2$ present in the acid dissolves in water to give carbonic acid.

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Question 41 Mark

What are polar stratospheric clouds (PSCs)?

Answer

Polar Stratospheric Clouds: PSC's are formed over Antarctica. They are of two types:
Type I clouds contain some solidified nitric acid trihydrate $\left(\mathrm{HNO}_3 ~3 \mathrm{H}_2 \mathrm{O}\right)$ formed at - $77^{\circ} \mathrm{C}$.
Type II clouds contain some ice, formed at $-85^{\circ} \mathrm{C}$.
These clouds play an important role in ozone depletion.

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Question 51 Mark

Why does rain water normally have a pH of 5.6? When does it become acid rain?

Answer

Rain has pH of about 5.6 due to dissolution of $\text{CO}_2$, gas in water.
$\text{CO}_2+\text{H}_2\text{O}\xrightarrow{\ \ \ \ \ \ \ \ \ }\text{H}_2\text{CO}_3$
$\text{H}_2\text{CO}_3\rightleftharpoons\text{2H}^++\text{CO}^{2-}_3$
When pH of rain falls below 5.6 it becomes acid rain.

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Question 61 Mark

What are pesticides and herbicides? Explain giving examples.

Answer

Pesticides : They are chemicals that are used to kill pests. They act by blocking the neurotransmission in the pest. e.g., $\text{DDT, BHC}$, etc.
Herbicides : They are chemicals such as $\mathrm{NaClO}_3, \mathrm{Na}_3 \mathrm{AsO}_3$ which are used to control the population of weeds in the fields.

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Question 71 Mark

A factory was started near a village. Suddenly villagers started feeling the presence of irritating vapours in the village and cases of headache, chest pain, cough, dryness of throat and breathing problems increased.

Explain what could have happened?
Give chemical reactions for the support of your explanation.

Answer

The gases evolved from the factory caused headache, chest pain cough, dryness of throat and breathing problems.
$2\text{C(s)}+\text{O}2\text{(g)}\xrightarrow{\ \ \ \ \ \ \ \ } 2\text{CO(g)}$

Carbon monoxide causes headache, nervousness, muscular weakness and weak eye sight.
$\text{S}+\text{O}_2\xrightarrow{\ \ \ \ \ }\text{SO}_2$
$2\text{SO}_2+\text{O}_2\xrightarrow{\ \ \ \ \ \ }\text{SO}_3$
Oxides of sulphur are irritating and can cause cough, dryness of throat and breathing problems.

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Question 81 Mark

Why 'photochemical smog' is called so?

Answer

It is because it is formed as a result of photochemical reaction (i.e. in the presence of sunlight) between oxides of nitrogen and hydrocarbons.

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Question 91 Mark

Why is hand pump water not considered as drinking water in these days? Explain.

Answer

Hand pump water is ground water. It is getting contaminated by fertilizers, pesticides, herbicides which are soluble in rain water and pass through the soil and enter underground water and make it unfit for drinking. Presence of Arsenic, excess of fluoride ions, heavy metals also make it unfit for drinking.

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Question 101 Mark

What is the role of $\mathrm{CO}_2$ in the 'green house effect'?

Answer

Heat from the sun after being absorbed by the earth is re-emitted by the earth and absorbed by $\text{CO}_2$ which then radiate it back to the earth, thus, maintaining the constant temperature of the earth.

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Question 111 Mark

What is the importance of measuring BOD of a water body?

Answer

BOD is a measure of level of pollution caused by organic biodegradable material present in the sample of given water. Low value of BOD indicates that water contains less organic matter.

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Question 121 Mark

What are biodegradable and non biodegradable pollutants? Give are example of each.

Answer

Those pollutants which are decomposed by micro organism are called biodegradable pollutants. e.g. detergents with linear alkyl chain are biodegradable water pollutants. Soaps are also biodegradable.
Non-biodegradable pollutants: Those pollutants which are not decomposed by micro-organisms are called non-biodegradable pollutants, e.g. Detergents with branched alkyl chain, DDT (insectide) are non-biodegradable.

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Question 131 Mark

Every year some people die by being in room containing a faulty heater that uses coal, or oil? How might the death occur?

Answer

The death occurs due to carbon monoxide which reacts with haemoglobin to form carboxy haemoglobin which does not act as oxygen carrier.

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Question 141 Mark

In winter, Sonia's parent burn coal in Angithi to keep the room warm. One late right, they wanted to keep angithi with burning coal inside the room. Sonia stopped them for doing so. She explained about the incomplete combustion of coal and harmful effects of burning coal in deficiency of oxygen.
Name the gas formed by incomplete combustion of coal. Also write the chemical reaction involved.
Suggest a reason as to why this gas is poisonous.

Answer

Carbon monoxide is formed by incomplete combustion of coal.

$2\text{C(s)}+\text{O}_2\text{(g)}\xrightarrow{\ \ \ \ \ \ \ }2\text{CO(g)}$

Carbon monoxide reacts with haemoglobin to form carboxy haemoglobin due to which delivery of oxygen to the organs and tissues is blocked. It results in headache, breathlessness, asphyxia $($cardio vascular disorder$)$ and even death in high concentration.

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Question 151 Mark

What is pneumoconiosis?

Answer

It is lung disease such a lung cancer, bronchital asthma, chronic brochities, etc caused by small sized particulates which enter into lung through nose and provide large surface area for adsorption of carcinogenic substances.

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Question 161 Mark

Ozone gas is heavier than air. Why does ozone layer not settle down near the earth?

Answer

Ozone layer is formed at an altitude of 25-30km from earth's surface by action of U.V. light on oxygen.
At this altitude force of gravitation is negligible that is why ozone does not settle near the earth.

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Question 171 Mark

Why are aquatic species more comfortable in cold water than warm water?

Answer

It is because dissolved oxygen is more in cold water than warm water.
Solubility of gas in liquid decreases with increase in temperature.

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Question 181 Mark

Photochemical smog occurs in warm, dry and sunny climate. Among $\text{SO}_2$, $\text{NO}_2$, $\text{O}_3$ and hydrocarbons which one is not amongst the components of photochemical smog and why?

Answer

$\text{SO}_2$ is reducing in nature and not obtained in sunny and dry climate. So, it is not a component of photochemical smog. It is a component of classical smog.

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Question 191 Mark

Why is ozone depletion mainly over Antartica?

Answer

This is because in other parts of stratosphere, chlorine free radicals combine away to form harmless products.
It Antarctica, compounds formed are converted into chlorine free radical again which cause ozone depletion.

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Question 201 Mark

What do you mean by Biochemical Oxygen Demand (BOD)?

Answer

Organic matter in water is biodegradable, i.e., it can be decomposed by the action of bacteria. Now, these bacteria need oxygen to decompose the organic waste. Thus, the amount of oxygen required by bacteria to breakdown the organic matter in a certain volume of a sample of water is called Biological Oxygen Demand (BOD) for that sample.

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Question 211 Mark

A trainee pilot was flying his plane in stratosphere. His senior advised him not to fly the aeroplane in the stratosphere.
Answer the following:

In your opinion, why the senior pilot advised his trainee pilot not to fly his plane in the stratosphere.
Write the possible reaction affecting stratosphere.

Answer

It is because No $($nitric oxide$)$ released by aeroplane will deplete ozone layer that is why aeroplane should not be flying in stratosphere.
$\text{N}_2+\text{O}_2\xrightarrow{\ \ \ \ }2\text{NO} [$nitric oxide$]$

$2\text{NO}+\text{O}_3\xrightarrow{\ \ \ \ \ }2\text{NO}_2+\text{O}_2 [$ozone depletion$]$
No reacts with ozone to form $\text{NO}_2$ and $\text{O}_2$.

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Question 221 Mark

Name the two greenhouse gases.
What is global warming?

Answer

Carbon dioxide and methane are green house gases.
Global warming when concentration of green house gases like $\text{CO}_2$ increases, these gases trap infrared radiations of sun and increase the temperature of the earth i.e. increase green house effect causing global warming. Global warming leads to abnormal changes in climate.

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Question 231 Mark

How can you apply green chemistry for the following:To control photochemical smog.

Answer

The most straight forward way to reduce or prevent the formation of photochemical smog is to minimise the release of oxides of nitrogen and hydrocarbons to the atmosphere. The following methods can be applied to minimise the oxides of nitrogen and hydrocarbons.

By fitting efficient catalytic converters in automobiles, the harmful gases are converted catalytically into harmless gases.
By spraying certain compounds into the atmosphere which generate free radicals that readily combine with the free radicals that initiate the reactions forming toxic compounds of the photochemical smog. The compound diethyl hydroxylamine has been found to possess smog inhibiting property.
Certain plants such as pinus, jiniparus, pyrus, vitis, etc., can metabolise oxides of nitrogen.

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Question 241 Mark

What is greenhouse effect?

Answer

The increase in temperature of atmosphere due to presence of gases like $\text{CH}_4$, $\text{CO}_2$ and water vapours which absorb infrared radiation is called greenhouse effect.

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Question 251 Mark

How can you apply green chemistry for the following:To reduce the consumption of petrol and diesel.

Answer

Instead of petrol and diesel, the use of CNG (Condensed Natural Gas) and LNG (Liquefied Natural Gas) has been preferred as they are pollution free fuels. The other sources such as hydrogen, ethyl alcohol, etc., can be tried in place of petrol and diesel.

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Question 261 Mark

What do you mean by sink? Give one example.
What is the sink for hydrocarbons and why?

Answer

Medium present in the environment that take up some amount of certain pollutants is called sink e.g. oceans act as sink for $\mathrm{SO}_2, \mathrm{CO}_2$ and $\mathrm{NO}_x$.
Chemical and photochemical reactions act as sink for hydrocarbons as these get decomposed in these reactions.

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Question 271 Mark

$\text{CO}_2$ is inert and harmless gas, yet it is thought to be a serious pollutant. Explain.

Answer

$\text{CO}_2$ absorbs infrared radiations from atmosphere which lead to global warming. If $\text{CO}_2$ level increases beyond 0.03%, the natural greenhouse balance may get disturbed. $\text{CO}_2$ is a major contributor to global warming, therefore, it is considered as serious pollutant.

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Question 281 Mark

A person was using water supplied by Municipality. Due to shortage of water he started using underground water. He felt laxative effect. What could be the cause?

Answer

The laxative effect is observed only when the sulphates present in water have concentration greater than 500ppm. Otherwise at moderate levels it is harmless.

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Question 291 Mark

What are primary and secondary pollutants of air?

Answer

Primary pollutants are those which remain as such in atmosphere e.g., NO.
Secondary pollutants are formed by reaction between primary pollutants e.g., PAN (peroxy acetyl nitrate).

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Question 301 Mark

Explain giving reasons "The presence of CO reduces the amount of haemoglobin available in the blood for carrying oxygen to the body cells."

Answer

Co combines with haemoglobin (Hb) of the red blood corpuscles (RBCs) about 300 times more readily than oxygen to form carboxyhaemoglobin complex, as follows
$\text{Hb}+\text{CO}\rightleftharpoons\text{HbCO}$
Thus, Hb is not able to combine with oxygen to form oxyhaemoglobin complex and hence, transport of oxygen to different body cells does not occur.

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Question 311 Mark

Dissolved oxygen in water is very important for aquatic life. What processes are responsible for the reduction of dissolved oxygen in water?

Answer

The discharge of human sewage and organic waste from pulp and paper industry and presence of leaves, grass, trash etc. in water due to run off result in phytoplankton growth. The microorganisms which decompose this organic matter need oxygen. Hence, the amount of oxygen in water of lakes etc. decreases.

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Question 321 Mark

How can you apply green chemistry for the following:To reduce use of synthetic detergents.

Answer

To reduce the use of synthetic detergents as cleaning agent, emphasis should be made on the use of soaps prepared of vegetable oils. The vegetable oils are biodegradable while detergents do not undergo biodegradation.

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Question 331 Mark

What is meant by polar vortex?

Answer

Polar Vortex: When polar stratospheric clouds are formed over Antarctica during winters, stable wind patterns, in the stratosphere are called polar vortex which encircle the continent.

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Question 341 Mark

Why is $\mathrm{SO}_2$ considered air pollutant?

Answer

$\mathrm{SO}_2$ reacts with $\mathrm{O}_2$ and $\mathrm{H}_2 \mathrm{O}$ to produce acid rain. $\mathrm{SO}_2$ also causes problem in breathing and irritation in eyes.

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Question 351 Mark

Why there is ozone depletion mainly over Antarctica?

Answer

This is because in other parts of the stratosphere, chlorine free radicals combine away with NO or $\mathrm{CH}_4$ but in Antarctica, the compounds formed are converted back into chlorine free radicals which deplete the ozone layer.

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Question 361 Mark

How can you apply green chemistry for the following:
To avoid use of halogenated solvents in drycleaning and that of chlorine in bleaching.

Answer

Solvents used to dry clean clothes are usually chlorinated compounds which are carcinogen. Suitable detergents which work in liquid carbon dioxide have been discovered to replace the chlorinated compounds. For bleaching of clothes in laundry, $\mathrm{H}_2 \mathrm{O}_2$ and not $\mathrm{Cl}_2$ is used which gives better results and is not harmful. Earlier, $\mathrm{Cl}_2$ gas was used for bleaching paper. Chlorine is highly toxic in nature. Its use has been replaced by $\mathrm{H}_2 \mathrm{O}_2$ in presence of a suitable catalyst.

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