4.7.2Electrochemistry
Practical- Preparation of Ethyl Ethanoate — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 5 parts Lesson 14 of 20 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Aim and Set-Up
Aim
- Aim To prepare a small sample of ethyl ethanoate from ethanoic acid and ethanol.
Reagents
- Reagents Ethanoic acid and ethanol are mixed with concentrated sulfuric acid, which acts as a catalyst.
Heating
- Heating The mixture is heated gently in a water bath or with an electric heater, because ethanol is highly flammable.
Distillation
- Distillation The ester is distilled off as it forms and collected in a beaker, because esters are volatile with low boiling points.
Equilibrium
- Equilibrium Removing ester from the mixture stops the reverse reaction, which shifts the equilibrium towards more ester.
Section 2 of 5Procedure
1
Mix ethanoic acid and ethanol in a flask, then carefully add the concentrated sulfuric acid.
2
Warm the mixture gently in a water bath or with an electric heater, never with a naked flame.
3
Collect the distillate in a beaker as the ester evaporates and condenses.
4
Smell the distillate by wafting the vapour towards the nose, to check for the sweet fruity smell of an ester.
Section 3 of 5Purification and Safety
Purification and Safety
Acid impurities
- Acid impurities Ethanoic acid and sulfuric acid carried over are removed by adding sodium carbonate solution until fizzing stops.
Ethanol impurity
- Ethanol impurity Calcium chloride solution is added to remove any residual ethanol from the ester.
Flammability
- Flammability Ethanol is flammable, so there must be no naked flames near the apparatus during heating.
Volatility
- Volatility Esters and ethanol evaporate easily, so the apparatus should be kept covered and handled with care.
Section 4 of 5Worked Example
Question Explain why the ester is distilled off as soon as it forms, and describe how its formation is confirmed.
- Esterification is reversible, so the ester can react back to acid and alcohol
- Distilling off the low-boiling ester removes product from the equilibrium mixture
- Removing product shifts the equilibrium to the right, increasing the yield of ester
- The distillate is smelt, and a sweet fruity smell confirms that an ester has formed
Answer Removing the ester drives the equilibrium towards more product, and the fruity smell of the distillate confirms that the ester formed.
Section 5 of 5Exam Checklist & Tips
4.7.2 – Key Points for the Exam
- Esterification The reaction of an alcohol with a carboxylic acid to form an ester and water.
- Distillation Separating a liquid from a mixture by heating it to vaporise it, then condensing the vapour.
- Water bath A container of hot water used to heat a flask gently and evenly.
- Sodium carbonate solution A solution used to neutralise and remove acid impurities.
- Calcium chloride solution A solution used to remove residual ethanol from the ester.
Common Mistakes
- Heating ethanol with a naked flame, which is dangerous because ethanol is flammable.
- Confusing the purposes of the two washing solutions: sodium carbonate removes acid, and calcium chloride removes ethanol.
- Keeping the ester in the reaction flask, which lets the reverse reaction occur and lowers the yield.
- Stating that the sulfuric acid is used up in the reaction; it acts as a catalyst.
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