Periodic Table and Energy 3
- Created by: GummyBear
- Created on: 14-03-17 19:05
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- THE PERIODIC TABLE AND ENERGY
- GROUP 7 - THE HALOGENS
- STATES AND COLOURS (room temperature)
- Chlorine = gas, pale yellow/green, and green vapour
- Bromine = liquid, brown/red and orange/brown vapour
- Iodine = solid, grey/black and purple (violet) vapour
- TESTING FOR HALIDE IONS
- Addition of AgNO3 (aq), dilute NH3 (aq) and concentrated NH3 (aq)
- Chloride = white precipitate, and precipitate dissolves with dilute NH3
- KCL(aq) + AgNO3(aq) = AgCL(s) + KNO3(aq)
- Bromide = cream precipitate, no change with dilute NH3, precipitate dissolves with concentrated NH3
- KBr(aq) + AgNO3(aq) = AgBr (s) + KNO3(aq)
- Iodide = pale yellow precipitate, no change wit dilute or concentrate NH3
- KI(aq) + AgNO3(aq) = AgI(s) + KNO3(aq)
- Use of Chlorine in water treatment
- ADVANTAGES
- Kills deadly microorganisms e.g. Cholera
- Keeps water pipes free of bacteria
- DISADVANTAGES
- The reactions of chlorine with organic compounds in the water produce THM's - e.g. cancer causing carcinogens
- Chlorine itself is toxic in large volumes
- ADVANTAGES
- TRENDS IN MELTING AND BOILING POINTS
- INCREASE DOWN THE GROUP - more electrons so stronger London dispersion forces between molecules so more energy is required to overcome them
- LONDON DISPERSION FORCES
- Uneven distribution of electrons causes a instantaneous dipole, this causes an induced dipole in surrounding molecules, therefroe creating a weak attractrion between moleucles
- REACTIVITY DECREASES DOWN THE GROUP
- STATES AND COLOURS (room temperature)
- GROUP 7 - THE HALOGEN
- HALOGEN DISPLACEMENTS
- Chlorine + Potassium Iodide - pink colour of I2
- Cl2 + 2KI = 2KCl + I2
- Bromine + Potassium iodide - Pink colour of I2
- Br2+ 2KI = 2KBr + I2
- Chlorine + Potassium Iodide - pink colour of I2
- HALOGEN DISPLACEMENTS
- GROUP 7 - THE HALOGENS
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