Chapter 12 - Chemical Analysis
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Define Purity [1]
A substance with nothing added to it [1]
Define a formulation [1]
A useful mixture, with each component having a specific function [1]
How can you determine whether a substance is pure or not? [2]
A subtance will melt/boil at a specific temperature [1] therefore having no impurities in the substance [1]
Give an example of how formulations are important in real life [2]
Formulations can carry out a function very effectively [1] e.g. paracetamol can relieve pain effectively [1]
Describe the test for CO2 and state the results [2]
Bubbling CO2 into limewater [1] Limewater turns cloudy in presence of CO2. [1]
Describe the test for chlorine and state the result [2]
Dipping damp litmus paper into chlorine mixture [1] Turns paper white in presence of CL2 [1]
Describe the test for hydrogen and state the results [2]
Placing a burning splint in a test tube with H2 [1] A squeaky pop sound in the presence of H2. [1]
Describe the test for O2, and state the results [2]
Placing a glowing splint in a test tube with O2 [1] Splint relights in the presences of O2. [1]
What is meant by a mobile and stationary phase? [2]
Mobile - When the molecules can move (e.g. Liquid) [1] Stationary - When the molecules cannot move (e.g. solids) [1]
What is chromatography? [1]
Separating substances into different components [1]
Describe the procedure of carrying out a chromatography [6]
Fill a beaker with a little bit of water [1] Using paper, use a few drops of ink and draw a baseline in pencil [1] Place the paper into the water [1] Wait for 5 minutes or until the ink stops moving [1] Measure the distance travelled by the substance and the distance travelled by the solvent and calculate an Rf value [1] Repeat 5 times and calculate a mean [1]
Which 2 factors affect time spent in each phase? [2] Explain what would happen to a subtance with a high solubility and low attractiveness [2]
Solubility in water [1] Attractiveness to paper [1] The substance would spend more time in the mobile phase [1] and less in the stationary phase [1].
State the equation used to calculate Rf values [1]
Distance of substance ÷ Distance of solvent [1]
Give the colour produced in the following flame tests: [5] 1. Lithium 2. Sodium 3. Potassium 4. Calcium 5. Copper
(Li) - Crimson [1] (Na) - Yellow [1] (K) - Lilac [1] (Ca) - Orange [1] (Cu) - Green [1]
Give the precipitate colour formed in the following sodium hydroxide tests: [6] 1. Aluminium 2. Magnesium 3. Calcium 4. Copper (II) 5. Iron (II) 6. Iron (III)
(Al) - White (Dissolves in NaOH) [1] (Mg) - White (Doesn’t dissolve) [1] (Ca) - White (Orange in Flame Test) [1] (Cu) - Blue [1] (Fe II) - Green [1] (Fe III) - Brown [1]
Give the test and result obtained from the tests for negative ions: [10] 1. Carbonate ions 2. Sulfate ions 3. Chloride 4. Bromide 5. Iodide
Carbonate: 1. Add an acid 2. Bubbles of CO2 Sulfate: 1. HCl + Barium Chloride 2. White precipitate Chloride: 1. Nitric acid + Silver nitrate 2. White precipitate Bromide 1. Same as chloride 2. Cream precipitate Iodide: 1. Same as chloride 2. Yellow precipitate