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Environmental Chemistry II: Water       Q.1)  Percentage of sodium chloride in sea water is ?  A. 0.02  B. 97  C. 2  D. Option 5  E. 3.4 Q.2)  Which salt does not cause the water to become hard?  A. Magnesium hydrogen carbonate  B. Calcium hydrogen carbonate  C. Sodium chloride  D. Magnesium sulphate Q.3)  Which of the followings is not a water born disease?  A. Hepatitis   B. Typhoid  C. Anemia  D. Dysentery Q.4)  Which one do you like?  A. Option 2  B. Option 1  C. Option 3  D. Option 4 Q.5)  Heating calcium hydrogen carbonate produces?  A. All of these  B. CaCO3  C. CO2  D. H2O Q.6)  Which salt causes temporary hardness in water?  A. Calcium sulphate  B. Both calcium sulphate and magnesium sulphate  C. Mag...

  Question: Describe some water born disease. Answer   Water borne diseases are given as follows. Cholera   Cholera is an intestinal disease. It is caused by bacteria such as vibrio cholera, E. coli etc., which may be present in water polluted with human waste. It  leads to vomiting and purging. Dysentery Dysentery is also stomach disease. It is caused by a parasite, Entamoeba. This infection is transmitted by fecal contamination of water or food by encysted organism. It can cause mild to severe abdominal cramps, diarrhea, chocolate colored stool with mucous and sometimes with blood. Jaundice Jaundice proceeds from obstruction of liver. Excess of bile from the liver enters in the blood and causes yellowness of skin and eyes. It causes loss of appetite, weakness and fatigue. Hepatitis Hepatitis is acute swelling of liver. It is caused by viruses and classified as hepatitis A, B, C, D and E. Hepatitis A and E spread through polluted wate...

Question: Describe different methods to remove permanent hardness in water. Answer. Methods to Remove Permanent Hardness Permanent hardness of water can be removed by following methods. i. By Adding Washing soda ii. By Ion Exchange Resins i. By Adding Washing soda Permanent hardness in water can be removed by adding washing soda. Calcium sulphate present in permanent hard water reacts with washing soda (Na2CO3.10H2O) to form insoluble calcium carbonates. Similarly, magnesium sulphate reacts with washing soda to give insoluble magnesium carbonate. Carbonates of both Mg and Ca can be removed by filtration method.   ii. By Ion Exchange Resins In this method, hard water is passed through a container filled with a suitable resin containing sodium ions (zeolite). Zeolite, also known as sodium aluminum silicate (Na2Z) is a naturally occurring as well as synthetic ion exchanger. When hard water is passed through zeolite bed, calcium and magnesium are removed from hard water by exchan...

Question: Describe different methods to remove temporary hardness of  water. Answer. Methods to remove temporary hardness Generally, there are two methods to remove temporary hardness. 1. By boiling 2. By adding slaked lime (Clark’s method) 1. By boiling   Temporary hardness of water can be removed by boiling. During the boiling of hard water, soluble calcium and magnesium hydrogen carbonates are converted into their insoluble carbonates which are separated by filtration. Thus, calcium and magnesium ions are removed as insoluble carbonates and water becomes soft.  However, this method is too expensive for removal of temporary hardness of water at large scale. 2. By adding slaked lime (Clark’s method) In Clark’s method, slaked lime (Ca(OH) 2 )  is added to temporary hard water. The slaked lime reacts with soluble calcium and magnesium hydrogen carbonates to form their insoluble carbonates which are separated by method of filtration. This meth...

Soft Water: Water that gives lather with soap easily and does not form scum is called soft water. Hard Water: Water that gives little lather with soap easily and forms scum is called soft water. How hard water is formed? Rainwater dissolves CO2 as it passes through atmosphere. Carbon dioxide reacts with water to form carbonic acid (weak acid).  When carbonated water passes over or through the rocks containing carbonates of calcium and magnesium, acid present in it reacts with these carbonates. As a result calcium hydrogen carbonate and magnesium hydrogen carbonate are formed which slowly dissolve rain water. Some rocks may contain gypsum (CaSO4.2H2O) or anhydride (CaSO4) or Kieserite (MgSO4.2H2O) which is sparingly soluble in water. The presence of these dissolved salts causes the water to become hard. Self-Assessment  1. List substances that cause hardness in water. 2. Differentiate between soft and hard water. Answer. 1. i. Calcium hydrogen...