C7.5

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  • Created by: amy_mair
  • Created on: 21-06-16 07:46
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  • C7.5
    • Analytical Procedures
      • Qualitative
        • 1. Qualitative analyis tells you which substances are present in a sample
        • 2. It does not tell you how much of each substance there is
      • Quantitative
        • 1. Quantitative analysis tells you how much of a substance there is
        • 2. It can be used to work out the molecular formula of the sample.
      • Chemical Analysis
        • 1. Usually you analyse just a sample of the material under the test there are some reasons for this...
          • 2. It might be very difficult to test all of the material if you have got an awful lot it
          • 3. Taking a sample also means taht if something goes wrong with the test, you can go back for another simple and try again
          • 4. A sample mist represent the bulk of the material being tested
      • Analysis
        • They are analysed in a solution
        • Samples are usually tested in solution
        • A solution is made by dissolving the sample in a solvent
        • There are 2 types of solution-aqeous and non aqueous
        • An aqueous solution means the solvent is water
        • An non aqueous solution means the solvent is anything other than water for example ethanol
      • Standerd Procedures
        • Everything is done the same way
        • 1. Standard procedures are agreed methods of working
        • 2. Standard procedures can be agreed within a company
        • 3. They are useful because wherever and whenever a test is done
        • 4. There are standard procedures for the collection and storage of a sample
    • Analysis- Chromatography
      • Phases
        • Chromatography is an analytical method used to separate the substance in a mixture.
        • You can then use it to identify a substance
        • There are a lot of different types of chromatography
          • A mobile phase: Where the molecules can move
          • A stationary phase: Where the molecules can not move
        • 1. The components in the mixture separate out as the mobile phase moves across the stationary phase
        • 2. How quickly a chemical moves depends on how it distributes itself between the 2 phases
        • 3.The molecules of each chemical constantly move between the 2 phases
        • 4. They are said to reach a dynamic equalibrium
      • Method
        • 1. The solvent moves up the paper
        • 2. The chemicals in the sample dissolve in the solvent and move between it and the paper
        • 3. When they are in the mobile phase the chemicals move up the paper with the solvent
        • 4. Before the solvent reaches the top the paper is removed from the beaker
        • 5. The different chemicals in the sample form separate spots on the paper
    • Analysis Chromatography
      • You can calculate the Rf for each chemical
        • 1. The result of chromatograpy analyis is called a chromatogram
        • 2.  Some of the spots on the chromatgram might by colourless. If they are you need to use a locating agent to show where they are
        • 3 You need to know how to work out the Rf values for spots on a chromatogram
        • Rf = distance travelled by solute / distance travelled by solvent
        • 4. Chromatography is often carried out to see if a certain substance is present in a mixure
        • 5. Chemists use substances called standard referance materials to check the identities of substances
      • Gas Chromatography
        • Gas Chromatography is used to analyse unknown substances
        • The mobile phase is an unreactive gas such as nitrogen
        • The stationary phase is a viscous liquid
        • 1. The unknown mixture is injected into a long tube coated on the inside with the sationary phase
        • 2. The mixture moves along the tube with the mobile phase untill it comes out the other end.
        • 3. The time it takes a chemical to travel through the tube it is called the retention time
        • 4. The retention time is different for each chemical
        • The distance along the x axis is the retention time
        • The peak height shows you how much of that chemical was in the sample
    • Analysis- Solution concentrations
      • Concentration= mass/volume
      • A standard solution is any solution hat you know the concentration of. Making a standard solution needs careful measuring
      • 1. First work out how many grams of solute you need by using the formula
      • 2. Carefully weigh out this mass of solute
      • 3. Add a small amount of ditilled water to the beaker and stir until all the solute has disolved
      • 4. Tip the solution into a volumetric flask
      • 5. Rince the beaker and stirring rod with distilled water and add to the fask
      • 6. Top flask up to correct volume
      • 7. Stopper the bottle and turn it upside down
      • 8. Check the meniscus again and add a drop or two of water
    • Analysis- Titration
      • How to get consistent readings
        • 1. Sometimes you get an outlier. This might be caused by faulty equipment or human error
        • 2. If your values are very similar you can be confident your results are reliable
        • 3. If they are more spread out, you can not be so certain of what the true value is
        • Then you need to repeat the results carefully
      • Interpreting
        • You can use titrations wo work out the identity of an unknown element in a compound
        • Step 1: First find out the mass of acid and the mass of alkali that react
        • Step 2: Find the relative formula mass of the known solute
        • Step 3: Find the relative formula mass of the unknown solute using the balanced equation
        • Step 4: Identify the metal hydroxide

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