2.3.2 Counter Ion “Most bacterial cell walls are charged with a negative charge‚ so most antibacterial polymers must be charged with a positive charge to facilitate the adsorption process. The composition of the counter ion‚ or polymer-linked ions‚ is used to balance the charge‚ it also affects the antibacterial activity. The counter ion has positive charge‚ which is a strong ion-pair with the polymer will inhibit the antibacterial activity because it will prevent the polymer from interacting with
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separate these two compounds column chromatography can be used to exploit the weaker polarity of 4-bromonitrobenzene. 4-Bromonitrobenzene has a weaker polarity due to its nitro group being in a para position thus lessening the electronegative effects of bromine on the other side of the ring by pulling electron density toward the ring1. Column
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Revision checklist for IGCSE Chemistry 0620 A guide for Students Revision checklist for IGCSE Chemistry 0620 A guide for students How to use this guide The guide describes what you need to know about your IGSCE Chemistry examination. It will help you to plan your revision programme for the theory examinations and will explain what the examiners are looking for in the answers you write. It can also be used to help you to revise by using tick boxes in Section 3‚ ‘What you need to know’‚ to check
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Science Division Course Offerings Astronomy (AST) AST 220. INTRODUCTION TO ASTRONOMY 4 cr. hrs.‚ Lec. 3‚ Lab. 2 This course covers the history of astronomy and the development of astronomical thought leading to the birth of modern astronomy and its most recent development. Emphasis is placed on the coverage of astronomical instruments and measuring technologies‚ the solar system‚ the Milky Way galaxy‚ important extra galactic objects and cosmology. Laboratory is required. Biology (BIO) BIO 103
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GLOBAL WARMING What Is Global Warming? Global warming is the warming of the earth through carbon dioxide (CO2) being pumped into the atmosphere from tailpipes and smokestacks. Then the gases trap heat like the glass in a greenhouse. This is where the term the “greenhouse effect” came from. What’s Happening Scientists say that the barrier insulating the continental ice caps is melting. “The impacts of warming temperatures in Antarctica
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Surname Centre No. Initial(s) Paper Reference 4 3 3 5 Candidate No. 2 H Signature Paper Reference(s) 4335/2H Examiner’s use only London Examinations IGCSE Team Leader’s use only Chemistry Paper 2H Higher Tier Wednesday 17 June 2009 – Morning Time: 2 hours Materials required for examination Nil Items included with question papers Nil Question Leave Number Blank 1 2 3 4 5 6 7 8 9 Instructions to Candidates In the boxes above‚ write your centre number‚ candidate number‚ your surname
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The SN2 reaction requires three qualities: a strong nucleophile‚ a good‚ unhindered leaving group‚ and a polar‚ aprotic solvent. For our reaction‚ we have all three bases covered. The nucleophile is an alkoxide‚ a deprotonated alcohol. Technically‚ because our alcohol is a phenol‚ the conjugate base is called a phenoxide. Phenol itself has a pKa of about 10‚ but our alcohol has more resonance opportunities‚ so the pKa is down around 8. This is sufficiently acidic for use of weak base like K2CO3 for
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6. What is the mass of 3.01 x 1023 atoms of sulfur? 7. What is the mass of 2.41 x 1024 molecules of water? 8. What is the formula mass (molar mass) of ammonium nitrate? 9. How many moles are in 56.2 grams of bromine gas? 10. What is the mass of 2.67 moles of sulfuric acid? 11. What is the mass of 3.5 moles of sodium sulfide? 12. Calculate the mass of 0.354 moles of ammonia‚ NH3. 13. Calculate the mass of 3.54 moles of sodium
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Louis Pasteur has always been famous in the medical field. A medical practitioner isn’t considered one without knowing who he is and what his contributions were. He was traditionally called as the progenitor of modern immunology‚ which with his discoveries paved a way for many experiments which helped the world in many ways. But who is this Louis Pasteur really? What influenced him into being a scientist? What are those wonders created by him? French chemist and microbiologist Louis Pasteur was
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hydrocarbons on the basis of physical and chemical properties; draw and differentiate between various conformations of ethane; appreciate the role of hydrocarbons as sources of energy and for other industrial applications; predict the formation of the addition products of unsymmetrical alkenes and alkynes on the basis of electronic mechanism; comprehend the structure of benzene‚ explain aromaticity and understand mechanism of electrophilic substitution reactions of benzene; predict the directive influence
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