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A-LEVEL CHEMISTRY EDEXCEL UNIT 6 (FULL) QUESTIONS AND ANSWERS WITH SOLUTIONS 2024
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A-LEVEL CHEMISTRY EDEXCEL UNIT 6 (FULL) QUESTIONS AND ANSWERS WITH SOLUTIONS 2024
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A-LEVEL CHEMISTRY EDEXCEL UNIT 6 (FULL) QUESTIONS AND ANSWERS WITH S OLUTIONS 2024 test for water - ANSWER CoCl2 = blue to pink CuSO4 = white to blue Give the reason why water is added when preparing benzoic acid - ANSWER To remove excess acyl chloride test for CO2 - ANSWER bubble gas through lime water (CaCOH)2 turns cloudy Explain in terms of change of state how the process of heating under reflux works - ANSWER as liquid boils vapour is cooled and condenses back to liquid absorbs water - ANSWER CaCl2 Give reasons why it is often necessary to heat chemicals under reflux - ANSWER 1. It prevents escape of reactants and products 2. Enables flammable liquids to be heated safely 3. Allows for a complete reaction Iodoform Test method - ANSWER - add I2 to alkaline solution til brown turns colourless - I2 and sodium hydroxide solution - add KI - positive = with carbonyl with methyl group = yellow ppt how species such as CH₃CHOH⁺ is formed from a molecule of compound X - ANSWER Species is formed by loss of CH₃ group Salt bridge - ANSWER filter paper and KNO3 suggest the best way to obtain some pure 1 -methyl -2,4-dinitrobenzene after the distillation. - ANSWER Fractional distillation followed by recrystallisation explain why when preparing nitrobenzene steps are taken so that the reaction mixture is always at or below room temperature - ANSWER To ensure only mono -substitution what neutralises excess acid? - ANSWER = sodium hydrogen carbonate = effervescence (CO2) Potassium manganate (VII) - ANSWER - indicator not required for titration - self indicating = colourless to pink explain why generally working from high to low concentration would be less accurate - ANSWER increases the possibility of contamination of ions due to residues from earlier experiments. Flame Test Method - ANSWER 1.) use nichrome wire 2.) dip wire in conc HCl to clean 3.) dip wire in solid 4.) place in hot bunsen flame and observe flame colour outline how you would use the apparatus to prepare 100cm³ of 0.1moldm⁻³ solution of X starting from 1moldm⁻³ of X. - ANSWER 1. Use a pipette to measure 10cm³ of the 1moldm ⁻³ of X. 2. Transfer this to a 100cm³ volumetric flask. 3. Make the solution up to the mark with distilled water and then mix. Test for Ammonia - ANSWER = damp red litmus paper turns blue = react with HCl gas > gives dense white smoke Name the reagents that are required for the iodoform test - ANSWER Sodium hydroxide and iodine solution . Recrystallization Method - ANSWER 1.) dissolve crystals in min. volume of hot ethyl ethanoate (solvent /water) 2.) filter to remove soluble impurities and allow to cool 3.) filter and wash with small amount of cold solvent (water bath and vacuum filtration) 4.) dry between filter paper or with warm oven Describe the procedure for carrying out the iodoform test. - ANSWER mix the reactants together and heat. Why is solid white? (trans metal) - ANSWER = d orbitals can't split therefore no colour as no ligand is present How would you show that the decomposition was complete - ANSWER Heat to a constant mass. Observation when a gas is evolved from a liquid - ANSWER Bubbles. Calibrate pH meter - ANSWER = use alkaline buffer solution and acidic buffer solution = then measure pH Why add water before acid? - ANSWER = acid reacts very exothermically with water = vigorous Observation when a gas is evolved from a solid. - ANSWER Steamy fumes. How to seal capillary tube? - ANSWER = heat one end of tube with bunsen flame until glass meltsThe benefits of buying summaries with Stuvia:
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