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The aim of the experiment is to identify 6 unknown colourless liquids by carrying out different chemical reactions on each of the liquids.

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Introduction

The aim of the experiment is to identify 6 unknown colourless liquids by carrying out different chemical reactions on each of the liquids. Flow chart showing tests/ reactions to identify the liquids. a) Bromoethane b) Butan-1- ol c) Cyclohexene d) Ethanoic Acid e) 2-Methylpropan-2-ol f) Water a b c d e f Forms CO2 gas and a white precipitate when reacting with sodium hydrogen carbonate. Yes No d- Ethanoic Acid a b c e f Decolourises bromine water Yes No c- Cyclohexene a b e f Forms a pale cream precipitate when reacting with silver nitrate solution. Yes No a- Bromoethane b e f Colour change occurs from orange to green when reacting with acidified potassium dichromate (vi) Yes No b- Butan-1-ol e f Turns blue cobalt chloride paper pink Yes No f- Water e Reacts with concentrated Hydrochloric acid, and Chlorine is substituted in place of the OH group. It then reacts with bromine water, decolourising the solution. Yes e- 2-Methylpropan-2-ol Background Information & Methods for Testing: Haloalkanes: Bromoethane is a haloalkane. Haloalkanes have the general formula of CnH2n+1X where the X represents the halogen. Bromoethane is a primary haloalkane. ...read more.

Middle

Equation for the reaction: K2CR2O7/H+ CH3CH2CH2CH2OH CH3CH2CH2CHO Butan-1-ol Heat [-2H] Butanal 2-Methylpropan-2-ol is a Tertiary Alcohol. Carbon2 has no hydrogen atoms, but has 3 alkyl groups and one OH group attached instead. Molecular Formula: C4H9OH = CH3CCH3OHCH3 Structural formula of 2-Methylpropan-2-ol: Carbon2 OH group Alkyl group To identify the tertiary alcohol, I will react 5cm3 of the liquid with 2cm3 of hydrochloric acid in a boiling tube and leave it at room temperature for 10 minutes. The tertiary alcohol will now have become a haloalkane because chlorine has replaced the OH group. After 10 minutes, I will react each of the liquids with bromine water. The solution that will decolourise will show that the original solution used was the tertiary alcohol, 2-Methylpropan-2-ol. (3) Equation for the reaction: HCl (aq) CH3CCH3OHCH3 CH3CCH3ClCH3 + H2O 2-Methylpropan-2-ol 2-Methyl-chloro-propane Water Carboxylic Acids: Ethanoic Acid is a Carboxylic Acid. Carboxylic acids are weak acids, hence only small amounts of its molecules dissociate in water. Carboxylic acids are however, stronger than alcohols due to the weakening of the O-H bond in the acid because of the presence of the carbonyl group and also because of the stability of the anion formed when the H+ ion leaves. ...read more.

Conclusion

If the solution decolourises, it will indicate that the original liquid used was Cyclohexene.(2) Equation for the reaction: C6H10 + Br2 C6H10Br2 Cyclohexene Bromine 1, 2-dibromohexane Water: Water is a pure substance made up of 2 hydrogen atoms and one oxygen atom. Water makes up 70% of the body and is very important to human life. Molecular Formula: H2O Structural Formula of Water: Oxygen atom. Hydrogen atoms To identify water, I will react 10cm3 the unknown substance in a beaker with blue cobalt chloride paper. If the paper turns pink after being in contact with the solution, it will prove the solution is water. The blue colour in the cobalt chloride paper is because of [CoCl4]2- ions. The blue [CoCl4]2- ions convert into [Co(H2O)6]2+ ions, which are pink in colour. (1) Safety: Source of hazard Hazard Precautions taken Acidified potassium dichromate (vi) Breathing in toxic fumes Conduct tests in a fume cupboard. Mixing chemicals Chemical may splash into eyes Wear safety goggles Acids Spillage/ contact with body Wear gloves and lab coat Apparatus: 6 boiling tubes Test tube holder Water bath 25cm3 beaker Measuring cylinder Spatula Bung Plastic tubing Silver nitrate Dilute alkali solution in ethanol Nitric acid Acidified potassium dichromate (VI) Hydrochloric acid Bromine water Sodium hydrogen carbonate (powdered) Limewater Blue cobalt chloride paper Six unidentified liquids- Bromoethane, Butan-1- ol, Cyclohexene, Ethanoic Acid, 2-Methylpropan-2-ol, Water. ...read more.

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