Chlorine

Chlorine is the non-metallic chemical element, symbol Cl, Chlorine is a highly poisonous, greenish yellow gas, about two and a half times as dense as air, and with a strong, sharp, choking odor.

1. University of Halabja College of Science Prepared by Karwan Omer May 2017 Chlorine Gas

2. Outlines 1- History 2- Introduction 3- Occurrence of chlorine 4- Position of chlorine in the periodic table 5- physical and chemical properties of chlorine 6- Electron configuration and bonding in Chlorine gas 7- Uses of Chlorine 8- Methods for the preparation of chlorine gas 9- Test for the identification chlorine gas 10- Reactions of chlorine 11- Health Effects of Chlorine

3. History Chlorine was  discovered  by Carl William Scheele at 1774 in Sweden.  T he Origin of name come from the Greek word " chloros " meaning " pale green “ Chlorine was discovered in 1774 by Carl William Scheele. He obtained it through the reaction of the mineral pyrolusite (manganese dioxide, MnO 2 ) with hydrochloric acid (HCl, then known as muriatic acid). MnO 2 (s) + 4HCl(aq) → Cl 2 (g) + MnCl 2 (aq) + 2H 2 O(l)

4. Scheele thought the resulting gas contained oxygen. He did not realize he had generated a previously unknown chemical element. It was not until 1810 that British scientist  , Sir Humphry Davy proposed and confirmed chlorine to be an element in 1810, and he also named the element.

5. Introduction Chlorine is the non-metallic chemical element, symbol Cl , Chlorine is a highly poisonous , greenish yellow gas , about two and a half times as dense as air, and with a strong, sharp, choking odor. It was, in fact, one of the first poisonous gases used in warfare—in 1915 during World War I.one of roughly 90 basic building blocks of matter. Naturally chemically reactive, chlorine’s tendency to combine with other elements and compounds has been used to produce thousands of essential products.

6. Chlorine gas Chlorine is rarely present in nature by itself as elemental chlorine , and typically exists bonded to other elements in the form of chemical compounds such as sodium chloride (table salt).  

7. In nature, chlorine is widely distributed over the  earth  in the form of the  salt  ( sodium chloride ) in sea  water . Halite  (NaCl) , sylvite ( KCl ) and carnallite (MgCl 2 .KCl.6H 2 O). average  concentration  of 0.67 oz (19 g) of chlorine in each liter of sea water, it is estimated that there are some 10 16  tons of chlorine in the world's oceans. 10 16   tons of chlorine in the world's oceans. Other compounds of chlorine occur as  minerals Occurrence of chlorine

8. Chlorine is the 17 th element on the periodic table. It is located in period 3 and group 17. Position of chlorine in the periodic table

9. Physical Properties of chlorine 1- Chlorine is a greenish-yellow gas at room temperature and  atmospheric pressure . 2- Density of chlorine ( 3.214 g/l) is two and a half times heavier than air 1.27 g/l. 3- Chlorine Is soluble in water. Its aqueous solution is called chlorine water which consists of a mixture of chlorine, hydrochloric acid (HCl), and hypochlorous acid ( HClO ). 4- The boiling point of chlorine is – 34.05°C. 5- The melting point of chlorine is –101°C.

10. Chemical Properties of chlorine 1-   Oxidation numbers of chlorine aside from the −1 oxidation state are +1, +3, +4, +5, +6, and +7 . in the following chlorine dioxide (ClO 2 ), chlorine perchlorate (Cl 2 O 4 ), dichlorine hexoxide (Cl 2 O 6 ), and dichlorine heptoxide (Cl 2 O 7 )—all highly reactive and unstable 2- the first  ionization energy  of chlorine is high 3- Chlorine is highly corrosive. 4- Chlorine displaces the heavier, less electronegative  halogens ,  bromine  and  iodine , from compounds. The displacement of bromides, for example, occurs according to the following equation:                                       5- Specific mixtures of chlorine and hydrogen can be explosive

11. The  electron configuration  of a chlorine  atom  ( Cl ) is as follows: 1s 2 2s 2 2p 6 3s 2 3p 5 [Ne]3s 2 3p 5 Electron configuration and bonding in Chlorine gas A  chlorine   atom  has  7   electrons  in its  outer shell .

12. Two  chlorine atoms  will each  share  one  electron to get a  full outer shell  and form a  stable   Cl 2   molecule . This is a picture of the  shared electrons  making a  covalent bond in a  chlorine molecule .  Chlorine  is a  simple molecule . By  sharing  the  two electrons  where the  shells touch each  chlorine   atom   can count  8 electrons  in its  outer shell .

13. Chlorine used as oxidizing agent and in substitution reactions. And for the manufacture of chlorates and it is important in organic chemistry, forming compounds such as chloroform, carbon tetrachloride, polyvinyl chloride, and synthetic rubber.  Chlorine gas is itself very poisonous, and was used as a chemical weapon during the War. Chlorine kills bacteria – it is a disinfectant. It is used to treat drinking water and swimming pool water. Pharmaceuticals : Chlorine chemistry is used in the production of a large proportional of all prescription drugs. Uses of Chlorine

14. Add concentrated hydrochloric acid dropwise onto a small quantity of potassium permanganate crystals (in a flask). Collect the chlorine gas by upward displacement of air in a hood. Reaction 2 KMnO 4 + 16 HCl  ==> 2 MnCl 2 + 2 KCl + 8 H 2 O + 5 Cl 2 Methods for the Preparation of chlorine gas

15. Chlorine may also be obtained by heating manganese dioxide with concentrated hydrochloric acid MnO 2   + 4HCl  è  MnCl 2 +2H 2 O + Cl 2 On industrial scale Cl 2 is obtained by the electrolysis of aqueous solution of NaCl called Brine. 2NaCl + 2H 2 O  è  Cl 2 +H 2 + 2NaOH

16. Tests for the identification chlorine gas   Chlorine  gas, Cl 2(g)  is green-yellow in  color . Chlorine has a characteristic sharp, choking smell . It also makes damp blue litmus paper turn red. Chlorine gas  is  extremely soluble  in  water. It  dissolves  to form   hydrochloric acid , a  strong acid ,   pH  = 1

17. 1- Reaction of Chlorine with Sodium Hydroxide Chlorine reacts with a hot solution of Sodium Hydroxide to give a mixture of Sodium Chloride and Sodium Chlorate. 3Cl 2 + 6 NaOH ==> 5 NaCl + NaClO 3 + 3 H 2 O 2- Reaction with water H 2 O + Cl 2 ==> HCl + HClO The Hypochlorous Acid, HClO, is not very stable and the solution readily decomcomposes, especially when exposed to sunlight, yielding Oxygen. 2 HClO ==> 2 HCl + O 2 Reactions of chlorine

18. 3- Oxidising Reaction of Chlorine Chlorine is a strong oxidising agent. Chlorine oxidises Iron (II) Chloride, FeCl 2 , to the salt containing Iron in the higher oxidation state Iron (III) Chloride, FeCl 3 . This is possible because Iron has a variable valency. 2 FeCl 2 + Cl 2 ==> 2 FeCl 3 4- Chlorine displaces the less electronegative Bromine and Iodine from their respective salts. Cl 2 + 2 KBr ==> 2 KCl + Br 2 5- Chlorine removes Hydrogen from the hydrides of non-metals, forming Hydrogen Chloride, and leaving the non-metal element. Cl 2 + H 2 S ==> 2 HCl + S

19. 6- Reaction of Chlorine with Hydrogen A mixture of Chlorine and Hydrogen explodes when exposed to sunlight to give Hydrogen Chloride. In the dark, no reaction occurs, so activation of the reaction by light energy is required . Cl 2 + H 2 ==> 2 HCl 7 - Halogenation of Organic compounds CH 4 + Cl 2 CH 3 Cl + HCl Unsaturated compounds, especially  alkenes  and  alkynes , add halogens: CH 2 = CH 2 + Cl 2 CH 2 Cl-CH 2 Cl

20. Health Effects of Chlorine Exposure, Concentration Health Effects (ppm in air) summarized in table bellow: Health Effects of Chlorine Health Effects Concentration (ppm in air) Mild mucous membrane irritation 1-3 ppm Upper respiratory tract irritation 5-15 ppm Immediate chest pain, vomiting, shortness of breath (dyspnea) and cough 30 ppm Inflammation of lung tissues (toxic pneumonitis) and fluid accumulation (pulmonary edema) 40-60 ppm Death within 30 minutes 430 ppm Death within a few minutes 1,000 ppm

21. References 1- Christe . K and Scheider .S (2016). Encyclopedia brittanica [ online] Available at : https :// www.britannica.com/science/chlorine/Physical-and-chemical-properties [Accessed 21 April 2017 ]. 2- Rutala , W.A. and Weber, D.J., 1997. Uses of inorganic hypochlorite (bleach) in health-care facilities.  Clinical microbiology reviews ,  10 (4), pp.597-610 . 3- Tundo , P., He, L.N., Lokteva , E. and Mota , C., 2016. Chemistry Beyond Chlorine. 4- Stringer , R. and Johnston, P., 2001.  Chlorine and the environment: An overview of the chlorine industry . Springer Science & Business Media.

22. Thanks for your attention