C3 Review PowerPoint Presentation

 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.

 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.

 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.

 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).

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.

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:

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.

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.