Presentation on theme: "On reaching this century and with the ease of information flow, the world seemed to be living in a global village full of a complicated information. We."— Presentation transcript:
On reaching this century and with the ease of information flow, the world seemed to be living in a global village full of a complicated information. We want as we are crossing to the 21 st century to reach by our educational system from linearity to systemic. So we searched for a new methodology growing the global way of thinking of students that is one of the most important requirements of globality. PREFACE
Systemic approach in teaching and learning chemistry (SATLC) is a new approach in teaching and learning for the 21 st century and means study of concepts or issues through interacted systems in which all relationships between concepts and issues are clear. It gives students a more global view of chemistry subjects, and improve their under-standing. It is found in 1997 as a result of joint cooperation between: Prof. Dr. A. F. M. Fahmy (Ain Shams University, Cairo, Egypt), and Prof. Dr. J. J. Logowski (University of Texas at Austing, USA). Concepts of practical Qualitative investigation of some anions and metal ions (Qualitative analysis of simple salts) are presented in this book under the name of green chemistry in lab. Experiments (GCLE) by making use of systemic methodology.
After studying this course, you are able to: (1) Save chemicals, and time. (2) Investigate metal ions qualitatively by different consecutive methods. (3) Investigate any compound in the frame of its chemical relations with related compounds. (4) Promotes of the principle of 3 R's (Reduce, Recover and Recycle). (5) Creation of the sense of the green chemistry. General Objectives
Methods available for detection of acid radicals or anions do not introduce the sense of the green chemistry. It must, however, be mentioned that it is possible to separate the anions into major groups depending upon solubilities of their silver, and or of barium salts. The following scheme has been found to work well in practice for detection of soluble anions in solution. Essentially the process employed may divided into two main experiments depending on the precipitation reactions with (BaCl 2 ) and (AgNO 3 ) solutions. Reactions of the acid radicals or anions in solution Reactions of the acid radicals or anions in solution
Unknown acid radical no ppt. Cl -, Br -, I -, S 2 O S --, NO 2 -, NO 3 - White ppt. on heating HCO 3 - White ppt. CO 3 --, SO PO , B 4 O 7 --, SO Exp.1 (BaCl 2 ) Insoluble in dil HNO 3 SO 4 -- Soluble in dil. HNO 3 CO 3 --, PO B 4 O or SO 3 -- No white ppt. B 4 O 7 -- or SO 3 -- white ppt. CO 3 --, PO white ppt. CO 3 -- Yellow ppt. PO Green solution SO 3 -- No Change in Color B 4 O 7 -- White ppt. Cl - Yellow ppt. I -, Br - Black ppt. S 2 O 3 --, S -- I-I- Br - S 2 O 3 -- S -- NO 2 - NO 3 - Exp. I-A (HNO 3 ) Exp. I-A-1 Exp. I-A-2 (AgNO 3 )Exp. I-A-3 (K 2 Cr 2 O 7 ) Exp. II-3 Exp. II (AgNO 3 ) no ppt. NO 2 -, NO 3 - KMnO 4 Exp. II-1 (CH 3 COO) 2 Pb +Mg SO 4 Exp. II-2 (CH 3 COO) 2 P b
To (1 ml) of the unknown solution add (2 ml) of BaCl 2 solution Exp. I Observation:
Add (2 ml) of dil HNO 3 to the precipitate obtained from exp. I. Exp. I-A Observation:
To (1 ml) of the original solution add (1 ml) of AgNO 3 solution Exp. I-A-2 Observation:
To (1 ml) of the original solution add (1 ml) of potassium dichromate and (1ml) of dil. Sulphuric acid Exp. I-A-3 Observation:
To (1 ml) of the unknown solution add (2 ml) of MgSO 4 solution. Exp. I-B Observation: White ppt. After heating. This means that HCO 3 - is present. Equation:
To (1 ml) of the unknown solution add (2ml) of AgNO 3 solution. Exp. II Observation:
To (1ml) of the original solution add (1ml) of lead acetate (CH 3 COO) 2 Pb solution. Exp. II-1 Observation: White ppt. of lead chloride soluble in boiling water. Equation: 2KCl + (CH 3 COO) 2 Pb PbCl 2 + 2CH 3 COOK.
To (1 ml) of the original solution add (1 ml) of lead acetate solution. Exp. II-2 Observation:
To differentiate between thiosulphate and sulphide anions: Exp. II-3 1) To (1 ml) of the original solution add (1 ml) of ferric chloride solution. Observation: Dark violet coloration (disappear by time). This confirm that (S 2 O 3 2- ) is present. The colour is due to sodium ferri-thiosulphate complex, Na[Fe (S 2 O 3 ) 2 ] 2) To (1 ml) of the original solution add (1 ml) of sodium nitroprusside solution.
Observation: Purple color formation. This confirm that (S 2- ) is present. Equation: Na 2 S + Na 2 [Fe(CN) 5 NO] Na 4 [Fe(CN) 5 NOS] If Exp. I and Exp. II gives no observation, the anion may be (NO 3 - or NO 2 - ) To differentiate carry out the following test. To (1 ml) of the unknown solution add (1 ml) of acidified potassium permanganate solution. Observation: If the color of potassium permanganate solution is discharged, then (NO 2 - ) radical is present.
Equation: 2KMnO 4 + 3H 2 SO 4 + 5NO 2 - K 2 SO 4 + 2MnSO 4 + 5NO H 2 O Reactions of the Metal Ions (Cations) Reactions of the Metal Ions (Cations) The Analytical Classification of the metal ions: The common metallic ions may be divided, for purposes of qualitative analysis, into a number of groups, which are distinguished according to their particular group reagent. The various groups are summarized in the following table.
It's assumed in the above table that the group reagents are added systematically to the solution from which the ions of the earlier groups have been removed or absent. When carrying out the various reactions of cations and anions, the student should always aim to keep the volumes and quantities of reagents as small as possible (semimicro technique). The advantages of semimicro scale technique, especially from the view point of economy of chemicals, apparatus, time and safe environments are so great that it must be strongly recommended to all.
Analysis of Group I Dil. HCl Group Analysis of Group I Dil. HCl Group Exp. I 1-a) To (1ml) of the unknown solution add (1ml). of dil. HCl solution. Observation: White ppt. of AgCl or PbCl 2. 1-b) Boiled the white ppt. obtained from (exp. 1-a). The ppt. soluble (Pb 2+ ) is present, Carry out systemic investigation (SI-1) to confirm the results The ppt. insoluble (Ag + ) is present, Carry out systemic investigation (SI-2) to confirm the results