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C3 Review PowerPoint Presentation
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Qualitative Analysis is where you find out what type of substance you have present. Quantitative Analysis is when you deduce the amount of unknown sample you have. Water samples contain IONIC COMPOUNDS which contain both CATIONS (positive) and ANIONS (negative ions). Ion tests must only give a positive result or one type of ion.
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Flame tests are commonly used for CATION (metals). Precipitate reactions can also be used by reaction the ionic solution with SODIUM HYDROXIDE as most metal hydroxides are insoluble in water.
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Testing for the Halogens ◦ This is performed by acidifying the sample with dilute Nitric Acid and then reacting with Silver Nitrate to form a precipitate. ◦ This reaction works by the Halogen displacing the Nitrate in Silver Nitrate with the Halogen. Testing for Ammonium ions (NH 4 + ) ◦ Warm the solution to release the Ammonium ions as a vapour ◦ It will turn damp red litmus paper blue.
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Ion identification is used in many different industries. For example: ◦ Water Industry to test for dissolved ions (both Halogens and other ions such as aluminium (linked to Alzheimer's disease). ◦ Blood testing to test for different ions (Iron linked to Anaemia, Sodium linked to kidney function).
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Types of Water Soft water – contains low levels of ions (Na, Mg) – easily produces a lather Hard water – contains lots of dissolved ions (Ca, Mg) – produced scum not lather – used lots of soap for cleaning Permanently hard water – cannot be easily softened Temporarily hard water – can be softened by boiling.
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Calculating Concentration Concentrations of ions are calculated generally in mgdm -3 or gdm -3. 1dm 3 is equal to 1000cm 3 (1 litre) To calculate concentration use the following formula:
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Temporarily hard water This water is softened by boiling. It converts the Calcium Hydrogen carbonate into insoluble Calcium Carbonate (lime scale). Softening the water improves its ability to form a lather and therefore reduce the amount of soap required.
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Softening Permanently hard water This can be performed using ION EXCHANGE. This involves Sodium ions (Na + ) in the resin displacing Calcium (Ca 2+ ) and Magnesium (Mg 2+ ) in the water sample and softening it.
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