ENVIRONMENTAL CHEMISTRY II: WATER

Chapter 15

ENVIRONMENTAL CHEMISTRY II: WATER

SOLVED

Test Yourself 15.1 (PROPERTIES OF WATER)

  1. No. i. What is capillary action?

Answer. Capillary action is the process by which water rises up from the roots of plants to leaves. This process is vital for the survival of the land plants.

  1. No. ii. Point out two properties of water that make it an excellent solvent.

Answer. The two properties of water that make it an excellent solvent are,

  • Polarity of water molecule
  • Exceptional hydrogen bonding ability
  1. No. iii. Why water molecule is polar?

Answer. Water molecule has a polar structure, i.e., one end of the molecule is partially positive while the other end is partially negative because of electronegative difference between oxygen and hydrogen atoms oxygen being more electronegative attracts the shared pair of electrons toward itself and attains partial negative charge while| hydrogen atom attains partial positive charge. In this way water molecule becomes polar.

 No. iv. Explain why non-ionic polar compounds are soluble in water?

Answer. Water can even dissolve non-ionic polar compounds having hydroxyl groups (-OH) like alcohols, organic acids, glucose, sugar, etc, by forming hydrogen bonds with them.

Test Yourself 15.2 (SOFT AND HARD WATER)

  1. No. i. What is an industrial waste?

Answer. The industrial effluent may be highly toxic organic chemicals, inorganic salts, heavy metals, mineral acids, oils and greases.

  1. No. ii. How water used as a cleaning agent in industries causes pollution?

Answer. Water used as cleaning agent in industries is directly discharged out. This water contains all kinds of toxic chemicals and detergents. When this used water enters lakes, streams, rivers or oceans it either gets dissolved or floats suspended in water. Even it gets deposited on the bed. Thus it causes water pollution.

  1. No. iii. Why use of detergents is increasing day by day?

Answer. Use of detergents for cleaning purposes is increasing day by day at domestic and industrial level. It is because; detergents have strong cleaning action than that of soap even in hard water. They can work even in acidic solutions. So, due to their better cleaning action their use is increasing.

  1. No. iv. How decaying plants consume oxygen?

Answer. Decaying plants being bio-degradable consume O2 present in water for decomposition process. As a result, O2 depletes in water that causes death of aquatic life.

  1. No. v. What is function of fertilizers?

Answer. Fertilizers are used to make up the deficiency of nitrogen, phosphorus, etc., of the soil because of intensive cultivation of crops in the recent years. They provide nutrients for the growth of plants.

  1. No. vi. How pesticides cause water pollution?

Answer. Pesticides are chemicals that are used either directly to kill or control the growth of pests. They are used in agricultural fields. When they run-off from these fields enter into pounds, streams or rivers, the salts containing phosphate ions causes the rapid growth of algae. When algae dies, bacteria consumes oxygen of the water for decomposition of algae. As & result, oxygen, depletes in the water that affects other organisms living in the water. Thus, pesticides cause water pollution.

Test Yourself 15.3 (WATER POLLUTION)

  1. No. i. Which salts are responsible for hardness of water?

Answer. Salts of divalent cations like Mg2+, Ca2 and anions like Cl-, S042-, HCO3– and COs2; for example, gypsum (CaSO4.2H2O) and lime stone (CaCO3) are responsible for hardness of water. Gypsum is sparingly soluble in water, while limestone is insoluble in water. However, in the presence of carbon dioxide small quantity of limestone is soluble in water according to the chemical reaction.

CaCO3(s) + CO2(g) + H2O(1)            Ca(HCO3)2(aq)

MgCO3(s) + CO2(g) + H2O(1)           Mg(HCO3) 2(aq)

  1. No. ii. Explain the chemistry of removing the temporary hardness by boiling water.

Answer. Temporary hardness of water is easily removed by boiling water. On boiling calcium bicarbonate Ca (HCO3)2 decomposes to produce insoluble calcium carbonate, which precipitates out of the solution and water becomes soft.

Ca (HC03) 2 ———> CaCO3 + H2O + CO2

  1. No. iii. What is the principle of removing permanent hardness of water?

Answer. Permanent hardness is because of Calcium (Ca+2) and magnesium (Mg+2) ions in water. The principle of removing permanent hardness is removing calcium and magnesium ions by using chemicals.

Calcium (Ca+2) and magnesium (Mg+2) ions are removed as insoluble salts by adding washing soda (Na2CO3) or sodium zeolite.

  1. No. iv. How addition of Na2CO3 removes permanent hardness of water?

Answer. The addition of washing soda removes the calcium and magnesium ions as the insoluble calcium and magnesium carbonates, respectively. As a result permanent hardness of water removes.

Na2CO3(aq) + CaSO4(aq)         CaCO3(s) + NaSO4(aq)

Na2CO3(aq) + MgSO4(aq)        MgCO3(s) + Na2SO4(aq)

No. v. How sodium zeolite softens water?

Answer. Sodium zeolite is a naturally occurring resin of sodium aluminum silicate NaAl (Si03)2, which can also be prepare artificially. It is used for softening of water at domestic as well as on; industrial scale. When water is passed through resin sodium ions o the resin are exchanged with the unwanted calcium and magnesium; ions of the hard water as shown in figure:

Ion exchange for removal of hard water ions

Na2 zeolite + CaSO4(aq) ———> Ca zeolite + Na2SO4(aq)

  1. No. vi. What do you mean by boiler scales? How are they removed?

Answer. Insoluble calcium and magnesium salts are deposited inside the boiler which is called boiler scales. They are removed by using acids which dissolve these salts.

Test Yourself 15.4 (WATERBRONE INFECTIOUS DISEASES)

  1. No. i. Define waterborne diseases.

Answer. Diseases that spread because of drinking polluted water or eating food prepared with polluted water are called waterborne diseases.

  1. No. ii. What is dysentery?

Answer. Dysentery is an intestinal disease which is typically caused by certain

bacteria or parasites. It is characterized by severe diarrhea that may be accompanied by blood or mucous.

  1. No. iii. Which of the bacteria causes cholera?

Answer. Cholera is an acute infection caused by the bacteria Vibrios cholerae, which may be found in water contaminated by human feaces.

Q.No. iv. What do you mean by fluorosis?

Answer. Fluorosis is a disease caused by the consumption of excess fluoride. Fluorosis can cause bones and teeth damage.

  1. No. v. What is hepatitis?

Answer. It is liver inflammation commonly caused by one of five viruses called hepatitis A, B, C, D, and E. Hepatitis A and E can be transmitted by contaminated water.

MULTIPLE CHOICE QUESTIONS

Put a (√) on the correct answer

/.     Which   one   of the   following properties   of water   is responsible for rising of water in plants?

  1. specific heat capacity b. surface tension
  2. excellent solvent action d. capillary action
  1. Specific heat capacity of water is
  2. 4.2 kJg-1 K-1 b. 4.2 Jg-1 K-1
  3. 2.4 kJg-1 K-1. d. 2.4 Jg-1 K-1
  1. Water dissolves non-ionic compound by
  2. ion-ion forces.  b. ion-dipole forces,
  3. dipole-dipole forces. d. hydrogen bonding.
  1. Temporary hardness is because of
  2. Ca(HCO3)2. b. CaCO3.
  3. MgCO3 d. MgSO4
  1. Temporary hardness is removed by adding
  2. quick lime.      b. slaked lime
  3. lime stone. d. lime water.
  1. Permanent hardness is removed by adding
  2. Na2 zeolite. b. soda lime
  3. lime water. d. quick lime.
  1. Which one   of the following   salts   makes   the water permanently hard?
  2. Na2CO3 b. NaHCO3
  3. Ca (HCO3) 2 d. CaSO4
  1. Rapid growth of algae in water bodies is because of detergent having
  2. carbonate salts. b. sulphonic acid salts
  3. sulphate salts. d. phosphate salts.
  1. Which one of the followings is not a reason of depletion Of from water?
  2. decaying of aquatic plants
  3. biodegradation of aquatic plants
  4. rapid growth of aquatic plants
  5. decomposition of aquatic plants
  1. Which one    of   the   following   diseases   causes    live inflammation?
  2. typhoid b. jaundice
  3. cholera d. hepatitis
  1. Which one of the following diseases causes severe diarrhea and can be fatal?
  2. jaundice b. dysentery
  3. cholera d. typhoid
  1. Which one of the following gases is used to destroy harmful bacteria in water?
  2. iodine b. chlorine
  3. fluorine d. bromine
  1. Which one of the following ions does not cause hardness in water?
  2. Ca2+ b. Mg2+
  3. Fe2+ d. Na+
  1. A disease that causes bone and tooth damage is:
  2. flourosis. b. hepatitis
  3. cholera. d. jaundice.
  1. Ionic compounds are soluble in water due to:
  2. hydrogen bonding. b. ion-dipole forces.
  3. dipole-dipole forces. d. dipole-induced dipole forces.
  1. The chemicals used to kill or control pests are called pesticides. They are:
  2. dangerous inorganic chemicals,
  3. dangerous organic chemicals,
  4. beneficial inorganic chemicals,
  5. beneficial organic chemicals.
  1. Which one of the following is incorrect?
  2. oceans contain 97%of world water, b. inland water is 0.2%
  3. glaciers and ice caps is 2.1% d. ground water is 0.8%
  1. 18. Portable water is only:
  2. 0.1% b. 0.2%
  3. 0.3%   d. 0.4%

   Sea water is unfit for drinking du& to:

  1. having dissolved salts
  2. having little salts
  3. having industrial effluents
  4. having agricultural effluents
  1. Which one of the following properties of water is incorrect?
  2. freezing point is 0°C
  3. density is 1 gem-3 at 4°C
  4. heat capacity 4.2 kJg1k-1
  5. boiling point is 100°C

ANSWER MCQs

  1. d 2. b 3. d       4. a       5. b       6. a       7. d       8. d 9. c       10. d     11. b      12. b     13. d     14. a     15. b        16. d
  2. a 18. b     19. a      20. c

 ANSWERS TO THE SHORT QUESTIONS.

  1. No.1. How water rises in plants?

Answer. Capillary action is the process by which water rises up from the roots of plants to leaves. This process is vital for the survival of the land plants.

  1. No.2. Which forces are responsible for dissolving polar substances in water?

Answer. The forces which are responsible for dissolving polar substance in water are polarity of water molecule and exceptional hydrogen bonding ability of water molecule.

  1. No.3. Why non-polar compounds are insoluble in water?

Answer. Many covalent substances like benzene, ether, octane, etc., which do not have polar ends or bonds are not attracted by water molecules. Therefore, non-polar compounds do not dissolve in water. Which is a polar solvent, So they do not follow the principle of like dissolves like

 No.4. How water dissolves sugar and alcohols?

Answer. Both sugar and alcohols contains hydroxyl group (OH-). Water molecule has two O-H bonds and two lone pairs that form hydrogen bonding with other compounds having hydroxyl groups. This unique behavior of water enables it to dissolve such compounds by forming hydrogen bonds with them.

  1. No.5. How lime stone dissolves in water?

Answer. Limestone is insoluble in water. However, in the presence of carbon dioxide small quantity of limestone is soluble in water according to the chemical reaction.

CaCO3(s) + CO2(g) + H2O(1)  Ca(HCO3) 2(aq)

  1. No.6. Differentiate between soft and hard water

Answer. Soft water is that which produced good lather with soap. While hard water is that which does not produce lather with soap?

Hard water consists of salts of divalent cations like Mg2+, Ca2+, and anions like Cl-, SO42- ,HCO3 and CO32- for example, gypsum (CaSO4.2H2O) and limestone (CaCO3) in water while soft water contains these salts.

  1. No.7. What are the causes of hardness in water?

Answer. Causes of hardness in water are presence of salts of divalent cations like Mg2+, Ca2+, and anions like Cl, SO42-, HCO3 and CO32 for example, gypsum (CaSO4.2H2O) and limestone (CaCO3) in water.

  1. No.8. What are the effects of temporary hardness in water?

Answer. Temporary hardness is because of presence of bicarbonate s of calcium and magnesium.

Effects of hard water

(i)       Hard water consumes large amount of soap in washing purposes.

(ii)      Drinking hard water causes stomach disorders.

(iii)     Hard water is unfit for use in steam engines, boilers and turbines because insoluble calcium and magnesium salts are deposited inside. Which is called scale? They are bad conductors of heat and hence more fuel is used. Insoluble calcium and magnesium sulphates not only reduce the efficiency of the engine but also cause the boiler to burst.

  1. No.9. Mention the disadvantages of detergents.

Answer. The detergent remains in the water for a long time and makes the water unfit for aquatic life. The phosphate salts present in detergents causes’ rapid growth of algae in water bodies, which floats over the surface of water. These plants ultimately die and decay. Decaying plants being bio-degradable consume O2 present in water. Thus, depletion of O2 results in death of aquatic life.

  1. No.10. What is difference between biodegradable and non-biodegradable substances?

Answer. The substances which can be decomposed by micro-organism like bacteria are called biodegradable substances. While, some of the detergents cannot be decomposed by micro-organisms like bacteria; they are called non-biodegradable substances.

  1. No.11. How detergents make the water unfit for aquatic life?

Answer. The phosphate salts present in detergents, causes rapid growth of algae in water bodies, which floats over the surface of water. These plants ultimately die and decay. Decaying plants being bio­degradable consume O2 present in water. Thus, depletion of O2 results in death of aquatic life. In this way detergents make the water unfit for aquatic life.

  1. No.12. Why pesticides are used?

Answer. Pesticides are used either directly to kill or control the growth of pests. Pests may be weeds herbs, insects, fungi, viruses, etc. They all damage crops and transmit diseases both to human beings and animals.

  1. No.13. What are the reasons of waterborne diseases?

Answer. Lack of proper sanitation facilities is the main cause of rapidly spreading of waterborne diseases. Water pollution may be due to toxins or microorganisms. Toxins are arsenic, mercury, lead and many organic chemicals. Microorganisms such as viruses, bacteria, protozoa and worms are the reasons of water borne diseases.

  1. No.14. How waterborne diseases can be prevented?

Answer. Waterborne diseases can be prevented by taking the following measures:

(i)       Provision of safe water: Drinking water must be properly treated and purified.

(ii)      Disposal of sewage: There must be adequate sanitary disposal of sewage. Any type of waste must not be thrown or discharged directly in water supplies or

reservoirs.

(iii)     Control of toxic chemicals: Chemical contamination can cause acute illness, but often toxic contaminants are slow poisons and carcinogens. There must be a strict- control over the use of pesticides and other chemicals.

ANSWERS TO THE LONG QUESTIONS

  1. No.1. How polarity of water molecule plays its role to dissolve the substances?

Answer. Water molecule has a polar structure, i.e., one end of the molecule is partially positive while the other end is partially negative because of electronegativity difference between oxygen and hydrogen atoms. All other polar substances are soluble in water, because the positive end of the substance is attracted by the negative end (O) of the water and negative end of the substance is attracted by the positive end (H+) of the water. The electrostatic forces attraction among the ions is overcome by the ion-dipole forces of attraction between ion and water molecules. In this way positive and negative ions of the compounds are pulled apart as shown in figure. Ultimately, these oppositely charged ions are surrounded by water molecules, thus separated and kept in solution. For example, most of the salts like NaCl, KC1, Na2SO4, etc., are soluble in water.

  1. Q. NO. Explain the methods of removing permanent hardness.

Answer. Permanent hardness can only be removed by using chemicals. Calcium (Ca2+) and magnesium (Mg2+) are removed as insoluble salts by adding washing soda (Na2CO3) or sodium zeolite.

  1. By using washing soda: The addition of washing soda removes the calcium and magnesium ions as the insoluble calcium and magnesium carbonates, respectively.

Na2CO3(aq) + CaSO4(aq)      CaCO3(s) +  Na2SO4(aq)

Na2CO3(aq) + MgSO4(aq)      MgCO3(s) + Na2SO4(aq)

Using Sodium Zeolite: Sodium zeolite is a naturally occurring resin of sodium aluminum silicate NaAl (SiO3)2, which can also be prepared artificially. It is used for softening of water at domestic as well as on industrial scale. When water is passed through resin sodium ions of the resin are exchanged with the unwanted calcium and magnesium ions of the hard water as shown in figure.

Na2 zeolite + CaSO4(aq)         Ca zeolite + Na2SO4(aq)

When resin is fully used up it can be regenerated by flushing it with concentrated solution of NaCl. The reverse process takes place because of high concentration of sodium ions.

Ca zeolite + 2NaCl         Na2 zeolite + CaCl2

  1. No.3. Explain the water pollution because of industrial waste.

Answer. Industrial units are installed to produce the desired substances (chemicals, cloth, leather goods, paper, plastic items, petrochemicals and rubber items) on commercial scale to meet the needs of the society. But unfortunately all the industrial units discharge their wastes (chemicals and solid materials) either to open ground or to water channels. This is called industrial effluent. The industrial effluent may be highly toxic organic chemicals, inorganic salts, heavy metals, mineral acids, oils and greases, etc. On the other hand, water used as cleaning agent in industries is directly discharged out. This water contains all kinds of toxic chemicals and detergents.

When these effluents or used water enter lakes, streams, rivers or oceans, they either get dissolved or float suspended in water. Even they get deposited on the bed. This results in the pollution of water, i.e.

(i)       They deteriorate the quality of water.

(ii)      They reduce the quantity of dissolved oxygen, ultimately affects aquatic life arid ecosystem.

(iii)     They can also seep down and affect the ground water deposits. They contaminate the water deposits. When this water is used by human beings it causes serious diseases like cancer .and gastro. This polluted water damages soil, crops, plants and animals.

(iv)     Heavy metals like cadmium, lead and mercury are toxic and health hazards for human beings. Acute cadmium poisoning causes high blood pressure, kidney damage and destruction of red blood cells. Acute lead poisoning causes disfunction of kidney, liver, brain, central nervous system and reproductive system. Mercury poisoning causes neurological damage.

  1. No.4. Justify the statement: house hold water is the reason of water pollution.

Answer. Use of detergents is increasing day by day for cleaning purposes in houses-and industries. It is because; detergents have strong cleaning action than that of soap even in hard water. They can work even in acidic solutions. But they have a major disadvantage over the soaps, as some of the detergents are non-biodegradable (cannot be decomposed by micro-organisms like bacteria). When household water containing these detergents is discharged in streams, ponds, lakes and rivers, it causes water pollution.

The detergent remains in the water for a long time and makes the water unfit for aquatic life. The phosphate salts present in detergents causes’ rapid growth of algae in water bodies, which floats over the surface of water. These plants ultimately die and decay. Decaying plants being bio-degradable consume O2 present in water. Thus, depletion of O2 results in death of aquatic life.

Domestic sewage contains a wide variety of dissolved and suspended impurities. They include food and vegetable waste, garbage, cans, bottles, chemical soaps, washing powder, etc. It also contains disease causing microbes. All these substances add to

water pollution.

  1. No.5. Explain agricultural effluents are fatal for aquatic I life.

Answer. Water pollution due to agricultural waste is because of use of fertilizers and pesticides. Fertilizers are used to make up the deficiency of nitrogen, phosphorus, etc., of the soil because of intensive cultivation of crops in the recent years.

On the other hand, pesticides are used either directly to kill or control the growth of pests. Pests may be weeds, herbs, insects, fungi, viruses, etc. They all damage crops and transmit diseases both to human beings and animals.

Agricultural effluents have dual effects:

(i)       Intensive cultivation of crops causes these chemicals from fertilizer and pesticides to seep into the ground water commonly called leaching process. The high nitrate contents in ground water are mainly because of irrigation run-off from agricultural fields.

(ii)      Sun-off from the agricultural land (where fertilizer and pesticides have been used), enters into ponds, streams or fivers. This water contains nitrate (NO3) and phosphate (PO43-) salts. These substances results in a rapid growth of algae, floating over the surface of water. They prevent the sunlight and air (oxygen) to reach up to aquatic life. When algae dies, and decompose bacteria consume oxygen of the water for decomposition. As a result oxygen depletes in the water. Aquatic animals feel suffocation and ultimately die due to insufficient supply of oxygen.

  1. No.6. Explain five important waterborne diseases. How can these be prevented?

Answer. The important waterborne diseases are

(i) Diarrhea diseases.

Intestinal diseases, such as cholera, that may cause dangerous dehydration. Diarrhea may be caused by viruses, bacteria, or parasites.

(ii) Cholera  

Cholera is an acute infection caused by the bacteria Vibrios choleroe, which may be found in water contaminated by human feaces. Cholera causes severe diarrhea and can be fatal.

(iii) Hepatitis

It is liver inflammation commonly caused by one of five viruses called hepatitis A, B, C, D, and E. Hepatitis A and E can be transmitted by contaminated water.

(iv) . Jaundice

Jaundice is caused by an excess of bile pigments in the blood. Liver ceases to function and eyes turn yellow- Patient feels weakness and fatigue.

(v) Typhoid

A dangerous, bacterial disease often spread by contaminated water or by food prepared with contaminated water.

Prevention of waterborne diseases

Waterborne diseases can be prevented by taking the following measures:

(i)       Provision of safe water: Drinking water must be properly treated and purified.

(ii)      Disposal of sewage: There must be adequate sanitary disposal of sewage. Any type of waste must not be thrown or discharged directly in water supplies or reservoirs.

(iii)     Control of toxic chemicals: Chemical contamination can cause acute illness but often toxic contaminants are slow poisons and carcinogens. There must be a strict control over the use of pesticides and other chemicals.

  1. No.7. Give some disadvantages of hard water.

Answer. Some disadvantages of hard water are:

(i)       Hard water consumes large amount of soap for washing purposes.

(ii)      Drinking hard water causes stomach disorders.

(iii)    Hard water is .unfit for use in steam engines, boilers and turbines because insoluble calcium and magnesium salts are deposited inside. They are bad conductors of electricity and hence more fuel is used. Insoluble calcium .and magnesium sulphates not only reduce the efficiency of the engine but also cause the boiler to burst,

  1. No.8. What is water pollution? Describe the effects of using polluted water.

Answer. Water pollution is a contamination of water bodies (e.g. lakes, rivers, oceans and ground water). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful Compounds.

Water pollution has the following effects:

(i)      It is hazardous to human health. Drinking polluted water can cause cholera, typhoid and diarrhea.

(ii)     The use polluted water is not only devastating for people but also for animals and birds.

(iii)    It causes rapid growth of algae. Death and decomposition of algae cause deficiency of oxygen in water that affects other organism living in water.

(iv)    It is damaging aquatic life, thus breaking a link in food chain.

(v)     It reduces the aesthetic quality of lakes and rivers.

(vi)    It is unfit for cleaning or washing purposes.

  1. No.9. Explain the reasons for considering water a universal solvent.

Answer. Water as Solvent

Water is the universal solvent because it can dissolve almost all the minerals. Its ability to dissolve substances is because of two unique properties of water:

(i)       polarity of water molecule;

(ii)      exceptional hydrogen bonding ability.

(i) Polar nature of water:

Water molecule has a polar structure, i.e., one end of the molecule is partially positive while the other end is partially negative because of electronegativity difference between oxygen and hydrogen atoms.

All other polar substances are soluble in water, because the positive H8+ end of the substance is attracted by the negative end (O5-) of the water and negative end of the substance is attracted by the positive end (H8+) of the water. The electrostatic attractions among the ions are overcome by the ion-dipole forces of attraction between ion and water molecules. In this way positive and negative ions of the compounds are pulled apart as shown in figure. Ultimately, these oppositely charged ions are surrounded by water molecules, thus separated and kept in solution. For example, most of the salts like NaCl, KC1, Na2SO4, etc., are soluble in water.

Dissolving process of a polar substance in water

On the other hand, many covalent substances like benzene, ether, octane, etc., which do not have polar ends or bonds are not attracted by water molecules. Therefore, non-polar compounds do not dissolve in water.

(ii) Extensive Hydrogen Bonding Ability

Water molecule is composed of oxygen and hydrogen atoms.

Because of two O-H bonds and two lone pairs, one H2O molecule can form hydrogen bonding with four other H2O molecules, which are arranged like tetrahedral around the H2O molecule as shown in Figure. This unique behavior of water enables it to dissolve many polar non-ionic compounds having hydroxyl group (-OH), like alcohols, organic acids, glucose, sugar etc. by forming hydrogen bonds with them.

Hydrogen bonding of water molecule

  1. No.10. Write a note on chemistry of cleaning swimming pool.

Answer. Swimming pools are cleaned by chlorination process. It is the addition of chlorine solution in swimming pools. Chlorine kills bacteria and other micro-organisms. Cl2 itself does not kill rather it dissociate in water to form hypoclorous acid (HOCI) and hydrochloric acid

C12 + H2O (1)         HOCl (aa) + H+ + Cl-(aq)

HOCI further ionizes to produce hypochlorite and proton

    HOCl(aq)   H+(aq) + OCl-(aa)

Both the products HOCI and OC1- kill bacteria and micro­organisms.

 

 

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